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keithb7

1938 Plymouth Transmission Rebuild

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Hi folks. I decided to start a fresh new thread on the re-bearing and re-seal of the tranny in my 1938 Plymouth. I started to touch on the topic in my car revival thread however I suspect it’s buried too deep to been seen my many. 

 

My goal is to completely reseal the tranny and change the main input and output bearings. I have progressed a bit in the job, however  this is my first time at this task. I really don’t want to screw up this tranny as I don’t have a spare. Also I want to do this and learn. It’s 1938, I don’t expect it’ll be too challenging. However I will tread carefully and ask lots of questions. I am hoping there is some experience here to guide me. 

 

I was wishful,  thinking I could change the main drive input bearing without disturbing too much of the tranny. I have been reading and that does not appear to be the case. Looks like the shafts are coming out.  

 

So far I have the front bearing cover and snap rings off. The park brake housing if off. Rear bearing retainer ring is out. I am ready to remove the rear main output bearing. I think I’ll try my slide hammer to get the bearing out of the park brake housing. Is that an acceptable method? 

 

I have an original Plymouth manual and a ‘40 era motors manual. Both mention being very careful when sliding then rear mainshaft out the back of the tranny housing. To avoid damage to the sliding clutch. Are there any other surprises to get this shaft out? The manual’s instructions are both pretty vague. Hoping I don’t see clutch gear springs and balls drop everywhere. 

 

Thx. There will be more q’s. Keith

 

 

 

 

A46FD3D9-66A7-4364-BC66-FC1056EA79E8.jpeg

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Isn't the purpose of the pilot bearing in the flywheel to accommodate the play in the shaft? I would need to to see a service spec for lateral runout before pulling the tranny apart.

 

Is the transmission noisy?

Edited by Sam Buchanan

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There was considerable drive train noise. I did find a very worn throw out bearing. This input bearing could also have been contributing. I can’t 100% say.  Turning it by hand, it does not feel smooth. I have no idea on the bearing age. Could be original. While I’m in there for the TO bearing it seemed to make sense to address these two main-shaft roller ball bearings

Edited by keithb7

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I’ll be watching with interest. I have noise In 1st and 2nd gear in my 36.

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Some pics up close of the bearing that is my current challenge. As mentioned, limited experience with how to pull this out. Toward the  shaft. Any tool advice appreciated. 

 

Maybe I can get my slide hammer to grab on the inner race edge and I can heave it out. May try that....No that won’t work. Tranny Input shaft is too long. In the way of a slide hammer. 

 

 

051DB486-CA91-469D-A11C-832BB3CC074C.jpeg

277D9917-6B76-4115-A658-BF569A0D72C9.jpeg

Edited by keithb7

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It's wise to replace both the input and output bearings IMO.

The replacement chinese /off shore bearings probably will not have as many roller balls and you might find the input shaft has nearly the same amount of movement as the old bearing.

There will always be some input shaft slop even with a new bearing.

The input shaft bearing is the most stressed bearing and can really rumble or howl if the balls and race get pitted.

Replace it or both..and check all other needle bearings carefully.

I now days won't use off shore ....bearings..junk IMO

..only MoPar/Timken/ Federal/ BCA etc old stock cosmolined bearings that look like good dry storage. 

 

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@Dodgeb4ya we’re aligned. Only a quality bearing will be re-installed. If I can get it out! Lol. 

 

A breakdown view is seen below here. Yellow line represents front bearing retainer housing that I removed. Green arrows (x2) point to bearing lock rings, both removed. Red arrow points to front bearing assembly to be replaced. 

 

 

17B611CC-477F-4A52-940C-CFD5594C907A.jpeg

Edited by keithb7

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Studying further and re-reading, I am grasping the inner workings. I wanted to understand this tranny. I think I got it. I will try to explain it to those interested, like I am. 

 

Gear set numbers are labeled in red. 1st/Rev sliding gear is on the main  shaft. You literally slide that gear by moving the shifter. There is no synchro mesh. It’ll grind if you try to downshift into first while still rolling. Unless you speed match the set perfectly to the matching countershaft gear. I won’t attempt to down shift to first. It’s just not built to take that shift. 

 

Look at the lovely twisted splines on the mainshaft that 1st/rev gear slides fore-aft on. That is a thing of beauty right there. Fine Chrysler engineering!

 

Gears 3 & 4 are in constant mesh with the countershaft. However they are not splined (locked) to the main shaft. You slide the clutch gear when shifting to lock and unlock 2nd or 3rd gear to the main shaft.  Direction of moving clutch gear indicated by green arrows that I drew on it. 

 

Notice all gears are spur cut and matched for quiet driving and increased strength. 

 

Good stuff. I’m enlightened. 

C789D906-7EB3-4CCF-8027-4CF788816554.jpeg

Edited by keithb7

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I have wedged against the input shaft outer bearing snap ring with one or two screw drivers.... while lightly tapping on the input shaft to work that bearing off the input shaft.

This after 1st removing the smaller snap ring on the input shaft.

Otherwise you need to drop the cluster gear down into the bottom of the case so the input shaft and bearing assembly can be removed out the front of the case.

Then press tap the bearing off the shaft.

Edited by Dodgeb4ya

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1 hour ago, Ranger said:

I’ll be watching with interest. I have noise In 1st and 2nd gear in my 36.

 

Ranger, I had noise in 1and 2 only as well. Did not hear it when in 3rd. 

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1st and 2 noise and some noise idling in neutral?... quiet in 3rd.... probably the input shaft bearing. Listen right at the top of the trans to bell housing with a long steel rod/long big screw driver or a wood dowel held against your ear.

Preferably with the rear wheels off the ground engine running in each gear there is noise.

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This method worked to get the  bearing free of the tranny housing. Used the large outer snap ring groove to anchor to, and a dead blow hammer. Now gotta get it off the shaft further. Getting close. 

 

 

B96F2002-E513-42D3-898E-4661F8EC0307.jpeg

67C5065C-F9F8-4F44-9C09-57DA07AA4705.jpeg

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I had 3 different 3 speeds in my 38.     First gear went in all three.       I gave the forth trans to someone in Pa.    I think I still have one more, but I went with a conversion, to a 5 speed Ranger trans....

5speed007.jpg

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You don't want to wedge the input shaft out of the case...no no..

Just pull the bearing and shaft out as much as it will let you from the case maybe 1/8" or so and wedge/hold that bearing firmly at that distance ...

Then tap with a brass hammer etc on the end of the input shaft till the shaft moves into the bearing 1/8". Wedge the bearing out a little more till it wont come out anymore ( usually 2nd time 1/4")  and repeat what you just did  driving the shaft into the bearing.. 3-4 times doing this will get the bearing off the input shaft.

No hard wedging...no big hammering is required and should not be done.

The input shaft is not to come out of the case and should not unless complete tear down is to be done... do not try to force it out of the case. .

Once again....Just keep pulling/wiggling  or lightly wedging the bearing and shaft out of the case as much as it will let you each time till it stops.

Then you need to prevent the bearing itself from being driven back into the case by holding it by the groove or I hold the bearing in place using the outer snap ring with screw drivers and or wedges. Then I lightly tap the input shaft into the bearing maybe 1/8" as that's as far as you can with out damaging the syncro or needle rollers. Then pull or wedge the bearing and shaft out again till it stops and repeat the process. As you do this the shaft stays in its place and the bearing keeps coming farther and farther off the shaft (about a (1-1/4") till it's free and in your hand.

Takes me at most 5 minutes to do this little operation as I've done many over the years..

Posi-Lok does make a $300.00 tool for this operation if you want one! It uses the snap ring groove to do it...special groove arms.

If you cannot do it safely take the whole trans apart! Don't damage anything.

Some random pics of different ways I hold the bearings if needed.....

Imput Shaft removal (2).JPG

Imput Shaft removal (5).JPG

Input shaft removal (2).JPG

Input shaft removal (1).JPG

Edited by Dodgeb4ya

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@Dodgeb4ya You method makes sense. I gave it a try. 

 

My initial technique did move the bearing up the shaft a fair aways. Just over ¼”.  I did not use excessive force. I don’t think I did any damage. After reading your post I blocked the tranny vertical and shimmed under the snap ring on the outer bearing housing. I started tapping on the input shaft with a deadblow soft hammer. I saw a little more movement of the bearing then it didn’t want to move any farther. A couple more taps, and the input  shaft was loose in the tranny. housing. It then easily was removed out the front, with the bearing still attached. Not great.

 

Upon inspection I can’t see any sign of any damage, marring or the like. Gears and sliding clutching ring and related parts all look good. I’ll take the shaft and bearing to a friend with a hydraulic press to complete the re & re on the shaft

 

Now I’m wondering if I’ll be able to get the input shaft back in through the front? Or wondering if I’ll have to take everything apart to go in from the rear?

 

 

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952FFC99-BD7D-41C0-BB63-AE2EF4947FFF.jpeg

Edited by keithb7

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The dead blow hammer does not have enough solid heavy weight mass to easily drive the input shaft quickly into the bearing. 

With the input shaft out of the case  and no bearing on it I'd try to see if the input shaft can be  put back in...it probably will not be easy to re-install as the cluster gear and input shaft synchro teeth interfere. Usually always preventing pulling out the input shaft.

You probably will now have to tear the trans apart...to re-install the input shaft and bearing assembly...safely.

 

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Yes, disassemble it and check your countershaft bearings. Usually noise in 1-2 but quiet in third is the countershaft, no power is transmitted through it in third, just freewheels so it’s quiet. Input or main shaft bearings will be noisy in every gear.   Unlikely but remotely possible the pocket bearing inside your input shaft could be worn.  

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"Son, are you sure you can get this back together?"    😁

 

Might as well go with a total rebuild.....eat the elephant one bite at a time......everything will be OK....and enjoy your new transmission!

Edited by Sam Buchanan

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Is it in yet?

I have just been reading a Truck Service Operation Time Schedule book.

 

Transmission (3 speed)- Recondition

Includes: Remove, disassemble completely, replace necessary parts, assemble, adjust and install.  4 hours.

 

Tony

 

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1 hour ago, Tony WestOZ said:

Is it in yet?

I have just been reading a Truck Service Operation Time Schedule book.

 

Transmission (3 speed)- Recondition

Includes: Remove, disassemble completely, replace necessary parts, assemble, adjust and install.  4 hours.

 

Tony

 

 

Lol. Not!

I need to place an order for the small parts kit. I’m in Canada. That’ll take 2 weeks to arrive. 

 

Gotta source USA made bearings. More delays. Darn job takes up most of my days. I’m warming up the idea of going all in. Could use some tips on countershaft pin and  shaft removal if anyone has any. That’ll be next after I get my parts orders placed. 

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If you have a shop manual it should explain everything. I completely rebuilt the same transmission for my '38 Chrysler many years ago. I had never had a transmission apart before but I just followed the shop manual and it really is very straightforward. I got some parts online and some from Rovon Auto Parts in Coquitlam, who specializes in Mopar parts. Message me if you want his address and phone number. If you have a parts book it helps getting quicker service as most suppliers have their inventory arranged numerically.

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Sure glad I dug in further. I removed the shift rails and slid the main output shaft out the rear. Then I had full access in the tranny  housing to the countershaft. I checked it for thrust clearance. Spec is .002” to .008”. I felt plenty more so I set up my dial indicator and measured .052”. Yikes. I proceeded to punch out the countershaft and was happy to find the front thrust washer was tearing itself apart. It was pretty thin and becoming cupped. It had already set an appointment for a self scheduled failure. 

 

Below are some pics. I’m all-in now. Glad too because  I’ve learned a lot. I feel that fixing your own stuff, going this deep is very rewarding.

 

Below you can see how much of the steel thrust washer is gone. It’s not supposed to have a raised center.  Last pic is rear thrust washer compared to the front. 

 

F6E197D9-D28B-416B-AFFB-D0FF12755A74.jpeg

 

 

CBD48F23-3190-44A7-B9A1-27DFC13B7DEE.jpeg

 

 

0E5B497F-AD1B-4BDD-B4A2-A4E44B032194.jpeg

Edited by keithb7

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