1938 Plymouth Transmission Rebuild

[keithb7]

Another developing issue, which I suspect is present in 99% of these old trannies is gear clashing at 1st gear. It is a sliding gear with no synchros. Previous owners were likely attempting to downshift into first gear while still rolling. Not good. You can see 1st gear teeth that have rounded nubs on the leading edges, where it makes initial contact with its mating gear. 

See pics below. I see some small chunks are missing from some teeth. I found the little pieces in the bottom of the case. 

 

Two mating gear areas, sliding 1st gear on main and mating gear on countershaft, are seen below here. 

 

Having limited experience with the longevity of these gears... Are you guys reusing gears like this? Or replacing them?  Keep in mind I am reviving the car. Not restoring it. I'm Building a local summer cruiser to enjoy. However I do prefer reliability.  The engine makes what,  maybe 120 HP when fresh? With no more future student drivers , I might be able to nurse these 2 gears along?

 

 Thx. Keith. 

 

 

 

 

Edited December 3, 2019 by keithb7

[Dodgeb4ya]

IMO use the gears. If one or two teeth were missing 1/5 or more of a tooth

...Replace the gears....in your case easy driving more than likely A-OK.

You might want to check both the counter shaft and the end of the main shaft where the needle rollers run on to be sure there is no damage to the surface case hardening on the shafts.

Pitting/spalling.

 

 

Edited December 3, 2019 by Dodgeb4ya

[kencombs]

7 hours ago, Dodgeb4ya said:

IMO use the gears. If one or two teeth were missing 1/5 or more of a tooth

...Replace the gears....in your case easy driving more than likely A-OK.

You might want to check both the counter shaft and the end of the main shaft where the needle rollers run on to be sure there is no damage to the surface case hardening on the shafts.

 

Agree with this advice.  I 'll add this:  Use a fine grinding stone on a die grinder, or similar tool, to smooth the edges of the chips.  That removes stress risers that can further damage the teeth and eases the engagement.  A slight taper and no sharp edges is the goal.  Back when 'three on the tree' replacement and repair was a staple of the auto salvage and garage business, we did hundreds like that.

 

 

[RobertKB]

I agree they are re-usable but with the tranny completely apart and if you can get the replacement gears at a reasonable price, why not replace? Ron Whiting at Rovon Auto Parts is very reasonable and all his parts are NOS or NORS and made in the US or Canada. His number is 604-936-9312. Having parts numbers ready always helps. I do have a parts manual that gives the numbers if you need help. Ron is a great guy, his prices are in Canadian dollars, and he ships quickly. Pretty sure he would have the small parts package you want as well as anything else. Good luck on the tranny project!

[westaus29]

Hi Keith, I am a bit late joining this conversation but as I have just recently overhauled my 38 Plymouth gearbox I will pass on my learnings. I had previously done my 29 gearbox which is a bit simpler. 

 

I stripped the gearbox mainly because it was out and accessible and I am trying to do a thorough restoration. It had always shifted fine and sounded fine. When I stripped it, I found missing and broken needle rollers inside the input shaft where the mainshaft slots in, but no apparent damage. So am very glad I did strip it. My bearings were ok and gears were in decent shape with light damage to first and reverse so I kept them. Before going further I ordered a small parts kit. These are available from Andy Bernbaum for $65 and include all needles, thrust washers and circlips. I bought mine thru eBay from Mopar-Direct because of postage issues to Aus and am happy with the quality.

 

First and most important is a couple of lengths of 3/4 inch hardwood dowel, one exactly 6-1/2 inches long for cluster gear and one 1-1/16 inch long for reverse idler, see pic below. The lengths of these match the overall assembled length of each gear including thrust washers and make assembly quick and easy.

 

 

Secondly I found it much easier to work on the gearbox by bolting it upright using a simple L bracket mounted in the vice as per pics below. It helped to have a swivel vice.

 

 

I was unable to remove the input shaft as a first step. It fouled the cluster gear and I dont like the idea of hammering the bearing as a way of getting that clearance, especially as my bearings were fine. So for me first step was to start at the back and remove the mainshaft complete with clutch assembly, taking care to hold the assembly together. Next I removed the countershaft, replacing it with the dowel, and let the cluster gear drop into the bottom of the box. This allowed me to remove the input shaft complete with bearing and circlip, then lift out the cluster gear assembly, then tap out the reverse idler shaft and likewise remove it ( cant quite remember if had to remove the reverse idler gear first???).

 

Assembly is the reverse. The dowels make it easy to insert the needles in the reverse idler and cluster gear, and position the thrust washers at each side. for the cluster gear, the steel thrust washers go next to the gear and needles, the bronze washers go on the outside. Note there are 31 needles to each bearing and I found they fit like a glove.

Pic Z1 shows needles being installed using dowel to hold them in place

 

 

Z2 shows thrust washers about to be installed

 

 

and Z3 shows the cluster assembly with thrust washers ready to go back in the box.

 

 

To insert the larger needles in the input shaft recess is not quite so easy, The last one feels like it wont go in but a bit of pressure from a wooden dowel and it should pop in. They fit so tight they wont fall out while you assemble them into the box. See pic Z4

 

 

Next install the cluster gear assembly and the reverse idler assembly, leaving the cluster gear in the bottom of the box. Install the input shaft, then lift the cluster gear into place and install the countershaft. Make sure countershaft and reverse idler shaft rear slots line up for the retainer plate. Then replace the mainshaft.

 

If you decide to pull the clutch gear apart you are in for some fun. I have some pics somewhere of a tool I used to reassemble it. As I recall it was a tin can of appropriate diameter. I could find it if you want.

 

Edited December 4, 2019 by westaus29
wrong data

[keithb7]

Thank-you @westaus29 for taking the time to write down your experience. The info is excellent and very helpful.

 

Are your wood dowels 3/4” diameter? 

[westaus29]

Yes 3/4 inch as bought from hardware store. Have just corrected reverse idler shaft length, had some extra bits in toolbox and picked the wrong one. Just took the top off my spare box and confirmed length is 1-1/16 inch. By the way, a bit of slop in bearings is to be expected as they are simple ball bearings. The input and mainshafts are steadied at both ends by bearings and arent going to move far.

[keithb7]

Hardwood, Oak ¾” dowel acquired.  Another good ol’ made in the USA part, I’m pretty sure. We don’t seem to grow or harvest any oak up here in Canada. 

I’m not planning to disassemble the clutch gear!  Hopefully I don’t have to. 

 

I ordered up USA SKF roller ball bearings. Numbers are:

 

Front main pinion (input) shaft 207ZNR. 

 

Output shaft bearing which is pressed into park brake housing 207S

Edited December 6, 2019 by keithb7

[westaus29]

Just remembered we have gone metric and dowel would be 19 mm not 3/4 inch. Difference of .05 mm not a problem. True Oak is hard to get here, we have "Tasmanian Oak" which is actually a native eucalypt, and in WA we have Jarrah which is a prized dark red very hard eucalypt.

 

Thanks for documenting the bearing numbers. I'll add it to my files.

Jim

[keithb7]

@westaus29 Reading though your instructions, there are a few things I can't quite wrap my head around.  When pushing the countershaft out, it was pretty tight. When putting it back in, if the slot for the lock plate is not lined up exactly as needed, how does one twist the countershaft to align?  

 

Also, what is the proper technique to push the reverse idler gear out the back of the case? I can't access it from both sides of the outside of the transmission case, as I did with the countershaft. Thanks, Keith

[westaus29]

I had a bit of trouble aligning the countershaft but have done it three times now, twice on my good box and once on the spare. The best way I found is to insert countershaft and reverse idler shaft  only part way so their far ends are just starting into the case. That holds everything together while you align the shafts and they are easier to twist. Tap the retainer plate in place at this stage and slowly tap both shafts in all the way. I put a bit of sealant here and there to hopefully minimise oil leakage

 

To get the reverse idler gear out I used a long brass drift inserted at an angle thru the input shaft hole. It doesnt seem to be as tight a fit as the countershaft.

[keithb7]

Following up on this thread, my tranny is coming together nicely. I am a little shocked and proud at the same time, being this is my first tranny rebuild. I won't celebrate yet until it's in the car and functioning properly. New input and output bearings installed. All new needle bearings installed. The kit I bought from Mopar Direct fit well. All new snap rings and thrust washers installed. It was a tricky tight fit to allow the cluster gear to drop down lower in the front, to allow the pinion to be installed. The wood dowels are a huge job aid and worked very well. The gears seem be shifting properly and moving as they should so far.  Next I'll install the park brake housing, all new gaskets and button this bad boy up...Riveting stuff!

 

Thanks @westaus29 for the tips. 

Edited January 4, 2020 by keithb7

[keithb7]

1 question. Does anyone know the recommended torque on the park  brake drum castellated nut? It mounts the drum to the tranny   output shaft . Just tight enough to line up the cotter pin holes?

 

I encourage you to go for it you’re considering rebuilding your manual transmission With a few common hand tools you can do this at home. Only task I left home for was the use of a hydraulic shop press to re and re main input and output bearings. I did not fab up a bracket to mount in a vice. Between my work bench and some blocking it was easily do-able. 

 

Possibly considered special tools I used: A slide hammer to remove the rear seal. (Not necessary just fast and easy) A brass hammer to tap pieces together. 1 pair of snap ring pliers.

 

Not so special stuff: A spacer tube for seal installation. (Seen in pic below). A bucket, some solvent and a brush. 2 oak dowels mentioned above. Some grease. New parts, gaskets, seals,  bearings are all readily available. 

 

About to push in the rear seal, in the pic. 

[keithb7]

I think she's gonna go! This vintage car stuff is terribly addicting. I can't hardly wait to get into the diff.

 

Edited January 5, 2020 by keithb7

[westaus29]

For recommended torques see ply33.com/Repair/torque for a good summary of available info. My Aussie manual does not show any torques. The mainshaft flange nut has to be good and tight. Specs say about 100 ft lb but you do have to line up for the split pin. I had to trim the pin short to get it into the recess. Good work!

[keithb7]

The park/emergency brake band was sent out for re-lining. The rebuilder told me the new brake band material is slightly thinner than what was originally used back in the day. He installed thin shim material around, behind the brake lining to maintain stock specs, and good hand brake performance.  See thin strip at base of arrow. 
 

 

 

[keithb7]

Something with the throwout  bearing is not sitting ok with me. I am wondering, what is the purpose of the 2 little wire springs on the side of the throwout bearing housing?  It seems the clutch fork can only fit around the throwout  bearing one particular way. Do I appear to have it laid out ok? Been a couple months since I took it out. I cannot recall exactly how it looked when I took it out. 

My manuals seem to skip any detail here. I am about to slide the tranny back in.  Thanks. 
 

 

Edited January 31, 2020 by keithb7

[Dodgeb4ya]

The release bearing and sleeve needs to be rotated 90 degree's. The fork pushes under the two fork curled springs.

A small dab of moly grease needs to be applied to each release bearing sleeve pad where the fork presses on.

The two clutch fork pads fit onto/against the two flat pads on the release bearing two flat machined pad surfaces.

Small amount of the same grease inside of the bearing sleeve so it slides freely on the trans bearing retainer.

Moly grease needs to be applied to the clutch fork and pivot ball stud surfaces too.

Edited January 31, 2020 by Dodgeb4ya

[Andydodge]

Keith........Dodgeb4ya beat me to it....the springs clip over the clutch fork and hold it onto the throwout bearing.........andyd

[keithb7]

Thanks folks. The spare throwout bearing and sleeve that I have here is from a 1953 Belvedere car. It won’t fit inside the ‘38 clutch fork if I spin it 90 degrees. 
 

I’m off to go find a new part. 

Edited January 31, 2020 by keithb7

[westaus29]

Your pic shows the clutch fork sitting on the bearing. It should be further back and turned 90 deg, sitting on the two arms of the bearing sleeve, held there by the spring clips. Are you saying the sleeve is too wide to fit there?

[keithb7]

@westaus29 The story behind this clutch fork issue and throwout bearing is I bought a bunch of used parts last fall for about $100. Most of the parts came out of a 1953 Plymouth.  I kept them around as needed in the future. When I got into my 1938 tranny & clutch I found a worn out throwout bearing. I looked in my spare parts stash and found I had what appeared to be a good, exact match. A throwout bearing and sleeve assembly. Upon reassembly of my '38 I found out that there was a difference.  The throwout sleeve housing is slightly wider. My '38 fork would not fit properly on the '53 sleeve.  As shown in the pics above.

 

I started shopping around for a proper new '38 throwout bearing. Every single part I need ends up costing me about $100 by the time it lands at my door. I'm in Canada and shipping charges are beyond ridiculous. At this point I am trying to revive the car, not restore it. I want to build a reliable driver and go from there. As you know, it's easy to spend $25K on a car worth $12K when you are done. This early in the game, I am trying to prevent that. Yet, how far I'll go in restoring the car in the future is to be determined. Getting back to the shift fork problem, I got to thinking, "Maybe I have the matching '53 shift fork?"  I dug around and found that indeed I did have it. I compared it to the original '38 shift fork. They are almost identical except for the wider spread at the fork. I swapped in the '53 shift fork and with the '53 throwout bearing, everything lined up nicely. The clutch linkage is smooth and seems to be working as it should. The real test will be the test drive coming up. 

 

Why would anyone utilize a used throwout bearing? Because in some instances at this stage,  I am willing to throw more time than money at my '38. LOL. 

 

Edited February 2, 2020 by keithb7

[keithb7]

Progress!! Test drive results coming soon...

 

 

[RobertKB]

5 hours ago, keithb7 said:

 

I started shopping around for a proper new '38 throwout bearing. Every single part I need ends up costing me about $100 by the time it lands at my door. I'm in Canada and shipping charges are beyond ridiculous.

 

 

I've suggested to you before to contact Rovon Auto Parts in Coquitlam, BC, not that far from you. He has most things you would need and his shipping is beyond reasonable.

[keithb7]

1 hour ago, RobertKB said:

 

I've suggested to you before to contact Rovon Auto Parts in Coquitlam, BC, not that far from you. He has most things you would need and his shipping is beyond reasonable.

Thanks. I have spoken to Ron. Three times over the past 3-4 months  I have contacted him to buy parts. He has not been able to provide so far for my parts requests. 

Edited February 2, 2020 by keithb7