39 special grinding in 2nd and 3rd gear

[buick looks fine for 39]

I've been asked by a friend to help with a transmission problem. The family is planning a roadtrip to Yellowstone , but the transmission is grinding badly in second and third gear. This car has had a frame off restoration by my friend who is an experienced mechanic. Most, if not all components , are nos in the gear box. First and reverse work fine, and if I remember correctly first to second shifts smoothly as well, but second to third grinds badly. Also downshifting from third to second is next to impossible. I checked the linkeage last fall and it seemed tight and installed correctly. Also with the motor not running the linkeage seemed to operate correctly. I found one wrong minor item which I corrected, but it didn't make any difference. After 20 minutes I ran out of time and had to quit. In the next few weeks I'm going to make another trip and attempt another repair. I know clutch drag can cause  hard shifting, but if the clutch was dragging wouldn't it cause grinding when shifted from first to reverse? I'd appreciate any input or advice.

 

                                                                                     Thanks

                                                                                     Leif

[Bloo]

First check the fluid level.

 

27 minutes ago, buick looks fine for 39 said:

but if the clutch was dragging wouldn't it cause grinding when shifted from first to reverse?

That is correct, but I would re-test it anyway.

 

Car idling not moving, put in first. Never let clutch up. Pull out of first. Wait about 2-3  seconds. Clutch pedal is still down. Try to shift back into first. Should not grind. Also adjust the clutch linkage to factory spec just to be sure it is OK.

 

27 minutes ago, buick looks fine for 39 said:

first to second shifts smoothly as well, but second to third grinds badly. Also downshifting from third to second is next to impossible.

These are symptoms of bad synchronizers on both second and third. What kind of oil is in it? I would try some synchromesh oil in it. It probably won't fix it but it might. Were the synchronizers new?

 

39 Buick transmissions have a bunch of one year only parts. As I understand it, one of the things they changed in 1939 was the taper of the synchro cones. I don't know for sure what year parts would physically fit in there, but it sure seems to me that you could get a taper mismatch by using a wrong year synchro or gear.

 

If it's not the oil or the clutch, I think you are tearing it down.

 

Edited February 10, 2022 by Bloo (see edit history)

[Jolly_John]

Hi Leif. Good of you to help this fellow '39 BUICK owner out. Bloo mentioned the possibility of an issue with the transmission oil. Certainly worth a check.

 

If I remember correctly (and you probably know), '39 was the first year BUICK spec'ed an EP gear lube for its transmissions. 90w, I believe. I wonder if whoever did the transmission work might have put in a straight gear oil, as was found in '38 and prior. If you can get a little of the lube on your finger (through the fill hole), you should be able to tell by the distinctive smell, if it's EP or not. Best of luck in your effort. John

[buick looks fine for 39]

Thanks guys I'll check the trans fluid and recheck the clutch. I also thought about a synchro taper mismatch, but I wanted to try easy fixes first. I'm open to any more additional ideas. This car runs beautifully except for the tranny. It belonged to a friend who passed away last year without being completed. Three guys including me finished the car for the family and this is  the last real hurdle to conquer.

 

                                                               Thanks again

                                                                Leif

[avgwarhawk]

Synchro are probably incorrect. I replaced a second gear synchro that had broken. The new synchro did not work. I tried every gear oil under the sun. Did not help.  At what speed is the engine idling? If the rpm is to high between shifts the synchro maybe having a hard time slowing the gear so to mesh without a grind. 

 

[Bloo]

You can check synchros on the bench when you have them out. Clean the synchro and the taper on the gear up real good. Put a little oil on the synchro. Push the two together while twisting. It should drag pretty hard or stop. If not, something is wrong.

[Mark Shaw]

Or, just shift it slowly like a no synchro tranny.

[buick looks fine for 39]

Thanks everyone for your imput, I tried to activate the like icon for y'all, but I ended up liking myself

[Larry Schramm]

5 hours ago, Mark Shaw said:

Or, just shift it slowly like a no synchro tranny.

 

What is a synchro tranny?

[EmTee]

[Lawrence Helfand]

My 41 century was balky into 2nd and I tried every lubricant out there over the years. Last year a forum member mentioned Redline 75/140 NS synthetic which is especially formulated for vintage manual transmissions. Bought some on the recommendation and my trans has never shifted better. I always assumed the more slippery the lube the better but synchromesh transmissions dont like too slippery as it turn out. I loved the results so much i used it in my Moto Guzzi trans and again superb results. No other lubricant comes close and its worth every penny! 

[EmTee]

On 2/12/2022 at 12:57 PM, Lawrence Helfand said:

I always assumed the more slippery the lube the better but synchromesh transmissions dont like too slippery as it turn out.

Yes, that's also the situation with my '04 Silverado.  I thought it would be good to change the transfer case oil since it was approaching 200 Kmi.  Since it uses ATF, I figured I'd "upgrade" it to Dexron VI.  Well, shortly afterwards it became increasingly reluctant to engage unless at a complete stop.  I found others on GM truck forums had observed the same; apparently the synthetic based Dexron VI is 'too slippery'.  Maybe this year I'll switch it over to Redline also.  I have been running Redline MTL in the T-10 in my '64 GP and it shifts like butter!  

[markewebb '39 Buick Team]

If needed, there is a 60 series 39 transmission for sale on Facebook.  You can find it on the "1939 Buick Owners and Enthusiasts" group page or search "1939 Buick transmission model 60 for sale$150"  

[Bloo]

That sounds like a good deal, but the car in the original post is a 40 series. It is a whole different transmission.

 

[avgwarhawk]

3 minutes ago, Bloo said:

That sounds like a good deal, but the car in the original post is a 40 series. It is a whole different transmission.

 

If it's similar to later 4 and 6 bolt transmissions it should fit. 6 bolt I believe is 1 inch longer. 

[Bloo]

That is a 6 bolt transmission in the picture, should fit 60-80-90. Car in the original post is a 40 and should have the physically smaller 5 bolt transmission.

 

Edited February 15, 2022 by Bloo (see edit history)

[Marty Roth]

As a temporary measure, and until the issue is resolved,

your friend could "Double Clutch",

not really a Lost Art.

Many of us here could step them through the procedure if needed.

[37_Roadmaster_C]

33 minutes ago, Marty Roth said:

As a temporary measure, and until the issue is resolved,

your friend could "Double Clutch",

not really a Lost Art.

Many of us here could step them through the procedure if needed.

Just STEP twice while shifting.  Sorry, could not pass it up 😇.

[Marty Roth]

On 2/15/2022 at 12:00 AM, 37_Roadmaster_C said:

Just STEP twice while shifting.  Sorry, could not pass it up 😇.

Move the shift lever to neutral-

release the clutch pedal-

depress the clutch pedal again-

shift to the other gear and release the clutch pedal (while approximating the newly-required engine RPMs)

 Thanks Robin,

and good to know the brakes on your Roadie work well 😎

[critterpainter]

Any chance that the shift cable is gummy or sticky.   I believe 39 is the only year that uses a cable to shift the gears.

[buick looks fine for 39]

Thanks for thinking of that, but the shift cable is smooth as silk 

[jvelde]

l use this gear oil in my ‘39, it really helps slow down the gears and the grinding is much less frequent. Shifting slowly was a plus.