PhilAndrews

'51 Chieftain - Transmission overhaul

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6 hours ago, john hess said:

Well Phil, on to positive side, when you get it fixed you will be more confident about going anywhere with the car. I was hesitant at first about opening up engine or transmission, ( manual ) but I am glad I did. I found some issues and fixed them. My intentions are to travel cross country with this car, and should any issues surface, I now have the knowledge to be able to repair or diagnose most issues. And with the help of this forum, if I don't know what's wrong, there's enough people connected to it, to help me(or anyone) to figure it out.             Keep us posted... Glad to hear you are in your new garage . John

 

 

 

John

 

That's rather where I'm at with this. First automatic transmission I've had to pull apart- the manual is actually really very good at demystifying it. 

Broken down into its modular parts each function becomes less difficult to comprehend. This thing definitely had some aircraft engineers working on it though, there are some really very aviation style designs, wrapped in inch-thick cast iron...

 

Overall it's not that bad to figure out. The trouble with me will be listening for odd noises and worrying over them.

 

Phil

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Oh dear.

20190804_113351.thumb.jpg.880e02cb3343c31a61321d4f18c01090.jpg

 

I have found the source of the swarf. I have a broken oil control ring. It has destroyed the center bearings and the drums.

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Anybody know a good source for hydramatic spares?

 

Phil

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Google FATSCO transmission parts in New Jersey. 

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20190804_161505.thumb.jpg.ff27cd306b0eb78561a3e61be55834a3.jpg

Root cause, this bearing failed, causing the other one to misalign and fail. The resulting off-center of both drums caused the fluid sleeve to come into forceful contact with the drums, melting the sleeve and fracturing the oil control ring.

 

20190804_161459.thumb.jpg.81425b75bf7de8275e1e8a541e829bd1.jpg

 

The inner bushing remains in good condition and as such held the primary epicyclic shaft true.

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So, the hubs of the clutches are toast and the fluid control sleeve and rings. The rest of the rotating parts are ok, the planet gears on that shaft are a bit worn but not horrible.

 

I've yet to pull the clutch packs apart to see how they are inside, hopefully they've not ingested too much swarf.

 

I'll see what FATSCO has to say on the matter, if they have the hubs and bushings individually. They do list the fluid sleeve new so that's a start.

 

Phil

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That's more like it, a la carte non-broken preloved parts.

 

Gonna pull the clutch packs out and see what shape they're in- if I can get away with just new hubs and bearings and fluid sleeve then that makes me happier.

 

Phil

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Shot an email off to fatsco this morning. Been bouncing back and forth and they've been incredibly helpful so far.

Looks like I may actually get this thing put back together.

 

Phil

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20190806_173525.thumb.jpg.1ad3b34c047c0f5a41cec932d75f4f4c.jpg

Friction material is no more good.

 

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Steels don't look too sharp, either.

 

The other drum is stuck, that's going to need something a bit more creative to shift.

 

Phil

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20190806_200211.thumb.jpg.5c20f078ee2c8417c519d5a6e159bd93.jpg

This put up a fight but came apart eventually. The friction discs have some material left but it's breaking up and the steels, although smooth, have heat fractures radiating out.

More on the list.

 

Phil

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20190807_112738_1.gif.c18696ce71988ad7fb49e283859106aa.gif

My big snap ring pliers arrived. They're going to make reassembly a lot easier than using my tiny little pliers. 

Between times they're quite therapeutic.

 

Phil

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Posted (edited)

One thing I would advise about reassembly, and this is for automatic transmissions in general, not just Hydra-Matics. Cleanliness is absolutely essential. A tiny spec of dust in the wrong place can ruin a rebuild. I know that is hard to believe since you find all sorts of crap from the steels and clutches laying in the pan of working transmissions. I don't know why that is different, but it is.

 

If you are not assembling in a clean, dust free room, and have to use a garage, like I used to do, close the doors and wet down the concrete floor and anything else that might put dust or dirt up in the air. Use a clean, clean, bench. If it is not a metal bench, put down some hard faced paper, something that won't release lint. Don't do part of the assembly and the rest later. Do it all at once and get it closed up.

 

Make sure your case, including any passages, is completely free of that swarf before you start.

 

Clean parts with clean solvent, blow them with compressed air, lubricate as necessary with ATF or transmission assembly lube, and put them in immediately. Do not get them near any shop rags! A tiny piece of lint can ruin your rebuild. Lint free rags are (or used to be) made for transmission rebuilding, but they can't be had on a minute's notice, and probably aren't a  good idea anyway. Banish rags, paper towels, etc from your shop while you assemble this.

 

Spool valves in valve bodies need to be able to drop out of their bores under their own weight. Don't be fooled by springs. Most of these spool valves are pressure balanced in actual operation. It really doesn't take anything to make one stick. Be careful cleaning them, Don't try to smooth or deburr uncooperative ones. The sharp edges are absolutely essential to keep tiny dust from wedging the valve and making it stick.

 

If you have some spool valves that won't fall out of their bores, don't just try to polish them or something, because the only way back from that mistake is to find another valve body. Take a step back and plan what to do next.

 

Good luck with your rebuild!

 

Edited by Bloo (see edit history)
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I had read through this in the manual and other rebuild advice elsewhere.

I'm unfortunately having to do this in my garage. I'm at the "get the swarf out of everything" stage, which is involving cleaning things down and putting them on new metal baking trays.

 

I'm going to be ordering the spares for it soon, at which point the clean/reassemble will be through the manual in one go as you say.

I've worked with precision hydraulics before and am familiar how little it takes to completely screw up a bore...

 

Any advice is absolutely welcome though. Thank you.

 

Phil

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Spent last night taking measurements of the thrust washers and doing some calculation.

The main shaft end-float is a compound of all the thrust washers and machine faces between the main center bearing and the back of the gearbox, so 4 washers and a shim.
When the gearbox was still all in one piece I measured the lash and it is 0.019", which is just outside of the 0.004-0.018" specification.
The thrust washers are quite worn. One is all the way through the copper coating, and regardless needs replacement. They measure 0.087" and 0.088" respectively, new they are 0.090" so I just ordered 2 new standard thickness ones and a slightly thicker main shaft end-float washer to bring me back into spec.

 

--Phil

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It is too late to work out by roadspeed, gear ratio and wheel diameter tonight.

 

What is the redline RPM of the Pontiac eight?

 

Something has me thinking 3750.

 

Phil

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Someone I met at Ames last year (who had a lot of road miles in flathead Pontiacs) told me "keep it below 3000  and everything will be fine".

 

Most engines generally should be able to sustain 80% of the RPM the horsepower was rated at.

 

Someone on the VCCA forum told me he could run his 1936 Eight 3250 RPM all day long, and often did on trips until it got wrecked. It was rebuilt and had aluminum pistons. Aluminum pistons put less load on the rod bearings at speed.

 

The good news is that HydraMatic cars are much less likely to spin the engine too fast, because they have a fourth gear.

 

How's that for a non-answer? :lol:

 

 

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Posted (edited)

Ha, yes. The book does not state what RPM max power is produced. 

 

Only reason is I want to set the needle on my tach. Technically it shouldn't go over redline because automatic but you never know if someone else is driving it with less sympathy than it deserves.

 

Following from what your wrote,I like to keep an engine cruising in the lower 2/3 of it's rev range if possible, but then again that comes from running small 4-cylinder engines (with design from the fifties, way to go stretching an engine design, Fiat...)

 

Phil

Edited by PhilAndrews (see edit history)

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48 minutes ago, PhilAndrews said:

Ha, yes. The book does not state what RPM max power is produced. 

 

Only reason is I want to set the needle on my tach. Technically it shouldn't go over redline because automatic but you never know if someone else is driving it with less sympathy than it deserves.

 

Following from what your wrote,I like to keep an engine cruising in the lower 2/3 of it's rev range if possible, but then again that comes from running small 4-cylinder engines (with design from the fifties, way to go stretching an engine design, Fiat...)

 

Phil

well pontiac max horsepower was read at 3600 rpms for straight eights 1949 to 1953, at 3800 rpms for 1954 straight eight, my 53 chieftain custom catalina would do 95 mph on a old tired 21 year old engine in 1974, with a 3.08 gear ratio at 90 mph the rpms were about 3400, with the highest gear ratio of 4.30 at 90 mph the rpms is 4750 according to the 49 to 54 pontiac shop manual. as a tech advisor, i have always told straight eight owners who have a tachometer to keep it no higher than 4000 rpms. 4th gear is not a overdrive gear, it's ratio is 1 to1, direct drive, no reduction.

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Posted (edited)

3750 is not an unreasonable limit.

 

I'm really wanting to keep it below 3000 anyway, that's really very fast and doesn't have much benefit in everyday driving. 

In the short distance I drove around it was happy 500-1000.

 

Other people may not appreciate that it doesn't share the same dynamic properties as more modern designs (oft with 6000-odd redlines). Just thinking of trying to preserve it a little.

 

Phil

Edited by PhilAndrews (see edit history)
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Posted (edited)
1 hour ago, PhilAndrews said:

3750 is not an unreasonable limit.

 

I'm really wanting to keep it below 3000 anyway, that's really very fast and doesn't have much benefit in everyday driving. 

In the short distance I drove around it was happy 500-1000.

 

Other people may not appreciate that it doesn't share the same dynamic properties as more modern designs (oft with 6000-odd redlines). Just thinking of trying to preserve it a little.

 

Phil

i remember my 53 cruising at 55 mph was only turning over about 2000 easy rpms

 

Edited by pontiac1953 (see edit history)
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I wasn't meaning to suggest that the HydraMatic had overdrive, just that HydraMatic cars usually came with higher final drive because they had 4 gears available, and could get away with it.

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I guess I'm old school... No tach. I just listen and feel.. most engines will tell you if you're pushing too hard, or chugging too low... John

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2 hours ago, john hess said:

I guess I'm old school... No tach. I just listen and feel.. most engines will tell you if you're pushing too hard, or chugging too low... John

My point is some people can't do that. So, a gauge with a red marker "not above here" is a help. Granted yes, you can feel it but still.

 

Phil

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4 hours ago, john hess said:

I guess I'm old school... No tach. I just listen and feel.. most engines will tell you if you're pushing too hard, or chugging too low... John

i drive truck, and i don't need a tach to tell me when to shift the gear, i can tell by the sound of the engine.

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Certainly not downing the use of a tach, I was just commenting on my driving habits.. also no need for a "check engine" light in my 53. It's called 'pretrip'..… I 'check engine' every day.. truck driver thing, I guess.... 

Hope the transmission rebuild works out. Ya got quite a project there Phil..

F

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