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Fluid Drive Transmission Question - 1950 Dodge w/ Gyromatic


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Hello all,

I have a 1950 Dodge Coronet w/ a flathead six. According to the owner's manual and the emblem on the side, the car has a Gyro-Matic transmission. However, while I can come to a stop w/out depressing the clutch, the car wont shift gears like the Gyro-matics are supposed to.

I've been having problems w/ my car having almost no accelerating power once it's in third gear (shifting manually of course) and I was thinking that perhaps the Gyro-matic was the culprit. Upon doing some research I've found some info that leads me to believe that I should have an electronic solenoid connected to my carburetor which controls the shifting on the Gyromatic transmission when the gas pedal is released/pressed at certain speeds. Well, I have no such solenoid whatsoever! Just a regular 1 barrel Stromberg.

So here's my question: is it possible that even though the emblems on my car say that is has the Gyro-matic, it might actually just have a fluid drive which would still require shifting? If not, is it possible that not having that solenoid could cause the car to never hit one of the four gears (seeing as how I can only manually shift into three) which would result in no power in third (since I'm basically skipping a gear).

Any help or insight anyone could provide would really be appreciated, I've taken it to a couple of people but they know nothing about these transmissions and are just completely stumped. They just tell me that my car shouldn't have much power w/ just the flat 6 and while I know this is true, mine has way too little top end power, even for a big car like mine w/ a straight six!

Thanks in advance,

Luke in Austin

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Luke:

These are really nice cars and terribly underrated. You'll enjoy yours once you get some bugs ironed out, and you've come to the right place. I started 20 years ago with a 1949 Dodge Coronet club coupe, and after a succession of old Chrysler products, went back to the Fluid Drive era deliberately, and I've put 130,000 miles on my 1950 DeSoto in the last 12 years.

It is possible someone removed the automatic gearbox from your car. I saw a 1950 Dodge Coronet club coupe like that once.

Fluid Drive was just the fluid coupling that allowed you to some to a stop with the depression the clutch, as you say. It was also designed to cushion the drivetrain against all the vibration the crude early roads inflicted on cars. They started putting automatic-shifting gearboxes behind the Fluid Drive in 1941, and it was refined into your M-6 "Gyromatic" in 1949.

The first step is to determine whether your car still has the M-6 automatic gearbox. Take a look at the passenger's side of the transmission and see if there are two soup-can-shaped devices sticking upward out of the gearbox, pointing toward the floorboard. If these devices are there, you have an automatic, and we'll go from there. Also, look for a wiring harness coming up from the transmission and connecting to the two little connectors on the spark coil with three wires running over to the carburetor.

These transmissions are work very nicely and are super-reliable. If neglected, they tend to have a few very predictable, easily corrected quirks. Also, once we get your transmission cured, I'll help you with your power problem. As you say, these were not racing cars at all, but I've driven my Dodge and DeSoto over the Colorado Rockies and the Cajon Pass here in California routinely, and I keep up with traffic, no problem. You may have a dragging brake shoe, and even more likely, you may have a dirty, out-of-adjustment parking brake on the rear of the transmission--very common and easily fixed. There are also questions of rear axle ratio I can tell you about.

You have a nice, comfortable road car that will serve you well, especially on long trips. My latest trip with the DeSoto was a meandering 6,300 miles between southern California and St. Paul, Minnesota.

Tell me what transmission you have, and we'll get started.

JON

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Jon,

Thanks so much!! I can't believe my luck in finding someone like you to help me!

I'm planning on taking a look at the transmission as soon as I get home today, but before I do, I thought I'd ask a quick question. I actually have the shop manual for my car and I was looking at a picture of the Gyromatic transmission. It shows two cylinders on the passenger side of the tranny; one being the "solenoid assembly" and the other, the "governer assembly". Are these the two soup can shaped things I should be looking for?

Again, thanks so much for being willing to help me out, I can't even tell you how much I appreciate it.

Regards,

Luke

<img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" />

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Luke:

Glad to help.

Yes, the solenoid and governor switch are exactly what I'm describing on the passenger's side of the transmission. If you have an automatic, I'll have quite a bit of easy-to-follow advice, and if you have a manual transmission, we can still talk about getting it to run a little healthier.

If you have an automatic, lift up the floor mat on the passenger's side, and you'll find two inspection covers--a big one on the side of the transmission hump back by the seat, and a little one higher on the firewall. The big one is the access to the electrical components on the transmission, and the little one is where you fill the Fluid Drive unit. These covers are easy to pull, and you might want to, just to familirize yourself with the car.

Let me know what you find.

JON

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Jon,

Well, I must say I'm shocked. After checking it out, it turns out I must not have the gyromatic transmission. While my car does have the access plates under the carpet on the passenger side, there are no electrical components on the transmission. Since the emblems on my car do say "gyro-matic" I'm pressuming that the transmission in my car must've been replaced at one time?

So I guess that's definitely not the problem w/ my lack of power. Any ideas?

Thanks again,

Luke

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Hi, Luke:

Sorry about the break in the conversation. I had to get caught up on some chores.

I've seen the automatic transmissions replaced in these cars before. It's too bad that it happened to your car, but at least what you now have is still a stock transmission, and if you really want to make the car perfect, look for a set of emblems that say Fluid Drive instead of Gyromatic.

On these three-speeds that were set up for Fluid Drive, First gear is so low that you'll find yourself using First very rarely. Just start out in Second and shift to Third.

I'd have to hear a lot more about your engine's condition, the car's general condition, and your level of experience with tuning and repairing cars. There are so many things your low power could be.

These cars are rolling history, and I'm glad to help anyone keep an original one on the road. E-mail me, and I'll give you my phone number. It'll save us a lot of typing if you answer a few questions for me and give me clearer picture of your Dodge's condition.

jrobinson@mscomm.com

JON

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  • 2 years later...
Guest De Soto Frank

Bill,

Any MoToR's or Chilton's manual covering 1950-1960 should have pics of the Fluid Drive and the semi-autos.

While the semi-automatic (M-6 Hydraulically-operated transmission) became an option for Dodge in '49, they continued to be offered with both "Dry-clutch" and 3-speed stick, and with Fluid Drive and 3-speed stick (Gyrol Fluid Drive).

If you're familiar with the regular "H-pattern" for the three-speed column shift, put in the clutch and try putting your Dodge into "first" (Lift the lever towards the rim of the steering wheel, and pull down). If it goes into "First", it's a plain-old 3-speed.

Semi-autos had the "first gear" position blocked-out: the lever will only go into "Reverse" / "Second"(lo-range) / "Third" (Hi-range).

Also take a look under the hood at the carb: if your car DID have the semi-auto, there should be some electrical terminals on the carb: two on top of the float bowl cover, and one by the throttle lever. There would also be a terminal block mounted to the air-cleaner support strap the runs from the driver's side of the air cleaner down to the cylinder head.

If you don't find any traces of these electrical gizmos under the hood, then it's pretty sure this car never had the semi-auto.

Good luck !

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  • 5 years later...
Guest sadida011
Luke:

These are really nice cars and terribly underrated. You'll enjoy yours once you get some bugs ironed out, and you've come to the right place. I started 20 years ago with a 1949 Dodge Coronet club coupe, and after a succession of old Chrysler products, went back to the Fluid Drive era deliberately, and I've put 130,000 miles on my 1950 DeSoto in the last 12 years.

It is possible someone removed the automatic gearbox from your car. I saw a 1950 Dodge Coronet club coupe like that once.

Fluid Drive was just the fluid coupling that allowed you to some to a stop with the depression the clutch, as you say. It was also designed to cushion the drivetrain against all the vibration the crude early roads inflicted on cars. They started putting automatic-shifting gearboxes behind the Fluid Drive in 1941, and it was refined into your M-6 "Gyromatic" in 1949.

The first step is to determine whether your car still has the M-6 automatic gearbox. Take a look at the passenger's side of the transmission and see if there are two soup-can-shaped devices sticking upward out of the gearbox, pointing toward the floorboard. If these devices are there, you have an automatic, and we'll go from there. Also, look for a wiring harness coming up from the transmission and connecting to the two little connectors on the spark coil with three wires running over to the carburetor.

These transmissions are work very nicely and are super-reliable. If neglected, they tend to have a few very predictable, easily corrected quirks. Also, once we get your transmission cured, I'll help you with your power problem. As you say, these were not racing cars at all, but I've driven my Dodge and DeSoto over the Colorado Rockies and the Cajon Pass here in California routinely, and I keep up with traffic, no problem. You may have a dragging brake shoe, and even more likely, you may have a dirty, out-of-adjustment parking brake on the rear of the transmission--very common and easily fixed. There are also questions of rear axle ratio I can tell you about.

You have a nice, comfortable road car that will serve you well, especially on long trips. My latest trip with the DeSoto was a meandering 6,300 miles between southern California and St. Paul, Minnesota.

Tell me what transmission you have, and we'll get started.

JON

Hello Jon,

I know that this is an older thread but I am work on a 1951 Dodge Coronet and I took off the inspection plates and I do have the two soup-can-shaped device. I want to keep the transmission can you help me services and get it ready for the road and not break it

Thanks

Newbie

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sadidaO11, there have been several in depth discussions of this transmission on the Chrysler and Dodge boards especially.

It was known as Gyromatic, Fluid Drive, or Tip Toe Shift on Dodge, Chrysler or DeSoto but all were the same transmission.

Do a search on the Chrysler board for Fluid Drive and look at some long threads from around 2OO8. There is a lot of good info on there. It took hours to type it all out and I dont want to do all that work over again.

Read the threads on how to service the transmission, and the best way to operate it. They should clear everything up. If you have any questions we will try to answer them but please, save yourself some time and do the search first.

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Guest sadida011

Rusty_OToole

Thanks for the help on how what to use in the search. I'm finding tons of information !!

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  • 2 years later...
Guest mrblueroads

i was wondering how to get to that sight or to learn just how to check and install fluid in my 51 coronet gyromatic. this site and this car is all new to me. i removed the little panel in the floorboard and all i see is a big hole in the bell houseing. i put my finger in and dont feel any fluid. i havent got it to shift to 2nd or 4th gear. i been on the road once, now i hear i have to let up on the gas to shift but i think i should check these fkuids before i go out again. the cars been siting bout 20 years. also i need to check the rearend dope i think. i would apreciate any help. i just joined this forum i hope i can find yalls replys if i should get any. thank yall.

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To check the fluid you got off to a good start. There is a plate on the side of the transmission tunnel. It is directly under the dash, on the passenger side. Roll back the carpet and there it is.

There should be a round hole in the bellhousing with a tin knockout plug in it, the kind electricians use to plug holes in electrical panels. It seems yours is missing.

Now you need to "bump" the starter until the fill plug comes into view. It is like a crankcase drain plug. Unscrew it with a socket wrench, IMPORTANT, stuff a rag around the hole first. You don't want to drop the plug down inside the bellhousing. I would hate to tell you how I found this out ha ha.

Get some oil, either straight #10 motor oil, or what most of us use now for Fluid Drive units and transmissions, TDH Tractor fluid, ISO22 or ISO32 grade. You can get it at farm supply, auto parts stores, or Walmart. TDH stands for transmission, differential and hydraulic fluid. ISO22 is better because it is thinner but ISO32 is easier to get. Either will be fine.

Pour the fluid in using a funnel, go easy, and when it runs over STOP it is full. There must be a little air space, that is why they put the filler hole at 2 o'clock. If the car is level it will have the right amount of fluid.

The transmission is filled separately. There is a pipe plug on the right side of the trans about half way up, like any typical manual trans. Stick your finger in the hole, if you touch oil it is fine. If not, pour oil in until it drips out. There is a hole in the floor for access to this area, or use some kind of pump or pressure bottle.

Trans oil should be changed every 10,000 miles. So if you don't know when it was changed last, this might be a good time to do it.

If you found my driving instructions I am surprised you didn't find the filling instructions. But, they were posted quite a while ago and they are not easy to find.

You might also just generally check over the wiring for loose wires, frayed or bare wires, broken wires etc. The old wires are usually pretty worn by now especially under the hood.

If the wiring is good and the trans and Fluid Drive are full of the correct oil, and you know how to drive the Fluid Drive trans, there go 90% of the problems up the flue.

There are only 2 other common problems, the idle must be set low, 400 - 500 RPM. This is normal for a Dodge flathead, very low for today's engines. The other thing is, the contacts in the governor can get dirty and oily after 50 or 60 years. You can carefully take the top off the governor, clean out the oil with brake clean spray or contact cleaner, and clean the points by dragging a strip of white typing paper between them. They are made of silver so do not use anything too harsh. Just polish them up. You will see a black streak on the paper, do it a few times and the paper will come out clean or nearly clean. This means the points are clean and polished. Ready to go for another 50 years.

The usual symptom of the governor not working, is the engine stalls when you come to a stop because the trans did not shift down. Leave it alone if the trans is working good, but if the governor stops working, you know what to do.

There is a wiring diagram in the Chrysler section someplace, do a search for fluid drive wiring diagram, if your wiring looks messed up or you think it needs to be replaced.

PS rear differential takes 2.9 pounds of oil, Hypoid 90 (summer) or Hypoid 80 (winter)

Edited by Rusty_OToole (see edit history)
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Guest mrblueroads

thaks for the help. sorry it took me awhile to log in then figure out how to reply. im trying to get rear end oil now but the parts store is not sure what im talking about. is that straight 90 or is there another numbe 75/90 they ask me. im going to napa maybe they will know. thanks again i didnt know the trans fill was seperate from the bell housing. when i look at my transmission i see what looks like 3 drain plugs, one on top of the other. is this what your talking about. im sorry i know so little about this but no one around here knows anything about it either. thank you so much for shareing your experience with me. not many folks know bout these cars.

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The 75/90 gear oil will be fine, better than anything they had back in 1950.

The rear axle is supposed to take 90(summer) or 80(winter) grade, Hypoid gear oil. I don't know if they make those anymore, but the 75/90 gear oil, or differential oil, hypoid oil, is the same thing. Notice that the 75/90 range covers the 80-90. This means you don't have to chose between summer and winter grade, the new type oil is good all year around.

There are different bolts and plugs on the transmission. There is one at the bottom to drain the oil. There is a similar plug half way up on the right side, this is the fill hole. I don't know how else to describe it. If you had a manual maybe there would be a picture. I don't know what you mean by 3 drain plugs one on top of the other. The drain and fill plugs are not grouped together, they are all by themselves.

Here is a picture of the M6 transmission. You can see a pipe plug at the bottom of the trans, sticking out to the side. That is the drain plug. Directly above it, half way up the side, is an identical pipe plug, which is the fill plug. In this pic it is hidden by the solenoid, you may just be able to see it peeking out a bit. On your trans you will see it easily, this is the best picture I could find.

http://www.google.ca/imgres?imgurl=http%3A%2F%2Fimg.photobucket.com%2Falbums%2Fv20%2Fpsatchwill%2FMy%2525201949%252520Chrysler%252520Royal%2FM6_FluidCoupler_Clutch_1.jpg&imgrefurl=http%3A%2F%2Fp15-d24.com%2Ftopic%2F5629-fluid-drive-unit-or-clutch%2F&h=480&w=640&tbnid=6K6T4KAbg-JZtM%3A&zoom=1&docid=60QfPLiDRnwLhM&ei=mBKeU56NArbesATtnIHAAg&tbm=isch&ved=0CCAQMygBMAE&iact=rc&uact=3&dur=1168&page=1&start=0&ndsp=10

It shows the transmission, clutch, and Fluid Drive unit. Notice that the Fluid Drive looks like a torque converter, the clutch is a conventional clutch, and the trans is completely separate from the Fluid Drive.

Edited by Rusty_OToole (see edit history)
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Guest mrblueroads

thanks. took my a while to find messages. got sum rearednd oil in. still didnt switch gears. i will track wires now. i think is electrical issue. im not sure where the govenor and points are youre talking about. that may be the problem. the carbs been worked on. so maybe the wires aint right. i got vids on youtube under mrblueroads if youre on there let us know. i will look at my trans again my has those soupe can looking things. im not seeing the three plugs on the one in the pic. i will look again, if i could get it to shift i would have a good ride. it runs good. thank you so much for your time. if i dont get right back to you it because i dont know how. if your on youtube let me know. thanks scott.

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"got sum rearednd oil in. still didnt switch gears. "

I showed you a picture and described exactly where the fill plug is, directly above the drain plug. If you pay my air fare I will fly down and point to it, other than that I don't think there is any more I can do.

Did you click on the link? Did you see the blue transmission in the picture? Does it look like your transmission?

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Guest mrblueroads

yea it looks like it. i couldnt get it to change gears today either. somehow its connected to the carb then to some kind of breaker mounted over the engine. one side of the breaker says battery so i ran a wire to the battery. then with the test light i could see power was geting to the solonoids. still no shift except when i get in low range and coast down the driveway it geared down and i heard the first solonoid click the one with the red wire on it. then the car died in the driveway and i left it there. thanks for your time im sorry to get on your nerves. i would pay the airfare to get it going. i cant find anybody that knows bout it round here.

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Did you find the fill plug? Is there oil in the trans? Is it the correct light oil (#10 or TDH)?

http://forums.aaca.org/attachment.php?attachmentid=122482&stc=1&thumb=1&d=1386280383

Here is a wiring diagram. It should help figure out the wiring.

The picture will open if you click on the link. Sorry it is so bad. You can make it bigger after you open it, if you hold down the Ctrl button at the bottom left corner of your keyboard, and rotate the thumb wheel on your mouse.

Here is a better wiring diagram plus a picture of the transmission. You have to follow this link, go down to post #3 and open the link at the bottom.

http://forums.aaca.org/f153/48-fluid-drive-trans-wont-upshift-275705.html

This is an Adobe Acrobat file which means, you must have Adobe Acrobat Reader on your computer. Sorry it is so complicated to get at the info, I am doing my best too.

Edited by Rusty_OToole (see edit history)
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The box contains a resistor and a circuit breaker.

The resistor goes between the coil's distributor side and the interrupter switch on the trans. This is the smallest of the 3 electric gizmos.

In other words: coil + ------------------- resistor--------------------- interrupter switch

The other part, the circuit breaker, goes between the coil's hot side and the solenoid. This is the big gizmo with 2 wires on it.

In other words: coil- ----------------------------- circuit breaker ------------------------- solenoid

Remember, on a Dodge the - is hot and the + is ground.

I forget the markings on the box, one is BAT, that goes to the coil -

If you clean it off good all 4 terminals are marked.

Edited by Rusty_OToole (see edit history)
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Guest mrblueroads

sorry it took me so long to figure out how to reply again, i have trouble finding the conversation. i been checking the electrical. the circuit breaker checks good. the wireing to the solonoid and govener seems good. the resistor may have a problem. i have a video by chrysler master tech how to service the hydrolic trans been useing. one test didnt work. they said remove the interuptor switch crank the car put in drive rang and acelerate and you should see the piston move foward to show the hydrolic system is working but so much oil was coming out and i never saw a piston. i might have put the oil in the wrong hole. there are 3 plugs on mine one at the top behind the govenor one under it in the middle of the trans and one directly under at the botton the drain i guess, i drained the oil put 10 oil in the top hole and it was hard to put in i put it in with a straw, at least 4 quarts. was it the wrong hole? can i have to much oil in it? is the middle plug the fill level or the low level? i cant tell by the vid i hace and i think its a 1948 vid anyway. i did not switch yet. i guess i will try to take the solonoid off and test it on the battery and try to check the points in the govenor. after that i got no more leads to check. im starting to have doubts it will shift. thanks for the help. i wish i could tell if i put to much oil in the wrong plug. i wish i could call you to save time, i will try to put my number here if it will let me 404 462 3723 scott thanks

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Guest mrblueroads

looks like i put the oil in the wrong plug from a thread i read you sent. i guess i should remove the middle plug and let it pour out. dern

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The plug is the level, stick your finger in the hole, if you touch oil it is fine. If too full let it drain out to the level of the hole. There is no dip stick or gauge.

Too much oil no good. You didn't do any harm if you did not drive it that way. It would probably blow the seals and all leak out if you drove too far.

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Guest mrblueroads

i will check the resistor, what do you mean by the distributor side of the coil? i see you got the plus sign, i dont think this is the original coil, would that matter?

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Guest mrblueroads

not sure of idle speed dont know how to check that are where the screw is. i think it might be to high. i just ran a wire from the gnd side of the resistor to the plus side of the coil. i think idle next then open the govener i reckon. i saw that solonoid work one time it downshifted while i was coasting down hill

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It does not matter if it is the original coil or not.

Since your car is a + ground, the + side of the coil has the wire to the distributor. The - side of the coil is the power side, fed from the key.

500 RPM is very low, today's cars idle about 800. If it sounds too slow, but smooth, it is probably about right. If it sounds "normal" it is probably too fast.

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Guest mrblueroads
It does not matter if it is the original coil or not.

Since your car is a + ground, the + side of the coil has the wire to the distributor. The - side of the coil is the power side, fed from the key.

500 RPM is very low, today's cars idle about 800. If it sounds too slow, but smooth, it is probably about right. If it sounds "normal" it is probably too fast.

thanks i will idel it down

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Guest mrblueroads

thanks i will slow it down . i took those poins out i cant see anything wrong but i found a new set will be here soon. maybe that plunger in the govenor is not moving them. i tried to move it up and down with my hand, it barley moves just a fraction. i dont know how far its supposed to move. when you push down a lot of little meatal blades push down and i stop because it looks like it could mess it up. i grab the middle shaft and pull up and down but it barely moves. i see no vent hole for oil

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It only has to move a fraction. If they are opening and closing, making and breaking the circuit, they are working. You can test them with a test light or multi meter. I never heard of them being replaced, only being cleaned, and then only rarely (every 25 to 50 years).

It should be clean, not full of oil. If oil has worked in, you can clean it off and dry it up with brake clean spray.

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Guest mrblueroads

it shifted today i dont know what made it shift but it did i want to thank you for your help. if you ever get this way stop a while. you have been a lot of help through this. it sliped a couple of tomes in 3rd but it went into 4th and we cruised around town, it will be on you tube friday morning if you want to look. thanks if there is anything i can do for you feel free to ask.

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  • 1 year later...
Guest Hispanikpanic

Hey guys, I'm new to the club and I have a question about transmission fluid for my 1950 Coronet.  Gyromatic --- the book says SAE 10 Motor oil, is that correct?

 

Thanks guys

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A lot of us use TDH tractor fluid, ISO32 grade. TDH stands for Transmission, Differential and Hydraulic. So it is formulated for this kind of application. ISO22 is even better (thinner) if you can find it.

 

10 motor oil is good too.  The TDH fluid may be better for the trans, it is easy to get from Walmart, auto parts stores and farm supply stores and it is cheaper than motor oil.

 

Either one will work.

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know i no it is a gyromatic i was looking for a picture of it was i am puting together a manual witch i will post when finshed so i need a picture of the trans and drive shaft and rear end

A picture of the M-6 trans and the fluid drive coupling.....

Bob

post-104482-0-52225000-1436841640_thumb.

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