Shimming mainshaft |
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NCtoy
Member Joined: 28 Aug. 2005 Location: NC Status: Offline Points: 507 |
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Posted: 05 Jan. 2019 at 3:47am |
I was having trouble with 2 gear, so I checked the end play on my mainshaft and came up with .053”.
Now, the service bulletin makes it sound like you can install a shim with the transmission in the jeep. The original shims would have been u shaped right? Every thread I look at, people are installing the shims while the transmission is getting rebuilt, with the output bearing pulled. I imagine I can cut the shims to slide over the shaft. Has anybody done this? McMaster Carr sells shims, but I need the inside and outside diameters. What size do I need?
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Joe Friday
Moderator Group Sponsor Member x 2 Joined: 26 Dec. 2010 Location: Jeep Central Status: Online Points: 3633 |
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I've never heard of using u shaped shims. The shims go between the rear main bearing and the mainshaft right? So you need to remove the transfer case to pull out the bearing to slide the shim over the shaft?
At the factory it was set by thickness of a snap ring? Are you missing the snap ring entirely? |
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NCtoy
Member Joined: 28 Aug. 2005 Location: NC Status: Offline Points: 507 |
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Maybe I’m misunderstanding what I’m reading. But the service bulletin about adjusting second gear problems makes it sound like it can be fixed without pulling the mainshaft out of the transmission. And this video rick stivers explicitly state that willys dealers did it without pulling the mainshaft with the use of an open shim, starting around the 7 minute mark. https://m.youtube.com/watch?v=vwbhR0aFzIs
Now I know the video is liable to be wrong, but seems like that would be the easy way to get a little more life out of a transmission. I’m collecting parts to try and rebuild a spare I have this year, I just need mine to run another year so I can get it all done. Edit: rereading the service bulletin without thinking about what stivers is claiming, it doesn’t say how to go about the shimming procedure. But if you’re taking it all apart anyway, why not rebuild it to start with?
Edited by NCtoy - 05 Jan. 2019 at 3:18pm |
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TERRY
Member Sponsor Member Joined: 22 May 2007 Location: BOULDER COLORADO Status: Offline Points: 3396 |
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When I rebuilt my T90, there was an omega shaped shim in place on the mainshaft. I recall reading somewhere on the forum that this was a commonly available item in the "old days". There was a tab on the top of the shim for gripping it with pliers to install. I guess you just gave the "legs" a little squeeze to hold it in place. Heard a rumor thar Sears sold them.
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BOULDER 48 2A
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ndnchf
Member Sponsor Member x 2 Joined: 22 Sep. 2017 Location: Virginia Status: Offline Points: 2177 |
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So what held these U - shims on the shaft? Was it just pinced?
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1948 CJ2A - It goes nowhere fast, but anywhere slow.
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Mike F
Member Joined: 12 Aug. 2018 Location: Longview wa Status: Offline Points: 684 |
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I may have watched every YouTube T90 rebuild video there is. The subject of one was shimming the main shaft? Seems like it was done to take care of the popping out second problem. Rick Stivers maybe.
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TERRY
Member Sponsor Member Joined: 22 May 2007 Location: BOULDER COLORADO Status: Offline Points: 3396 |
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I found my old one in the garage, here are photos loose and installed. I did not squeeze the ends slightly as I expect was done. |
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BOULDER 48 2A
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mbullism
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I feel like I'm looking at a unicorn...
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Those who do not learn from history are doomed to repeat it... Welcome to 1930's Germany
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NCtoy
Member Joined: 28 Aug. 2005 Location: NC Status: Offline Points: 507 |
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I’m going to head down to the local sears and buy up all they have in stock.
Now that I know it can and was done that way, my idea is to cut an opening in a regular round shim and slap it in there. Once I pull the nut on the back of the output shaft up tight it shouldn’t be able to go anywhere. Any chance you can measure the inside and outside diameters on that one?
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TERRY
Member Sponsor Member Joined: 22 May 2007 Location: BOULDER COLORADO Status: Offline Points: 3396 |
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It has been deformed from its original dimensions, so measurement won't be accurate. I would go off of the OD of the shaft, and allow enough width for the OD to go beyond the shoulder on the mainshaft as in the photos. The OD should not be critical as there isn"t anything to interfere with. I get ID of approx. 1.5" and it is 1/4" wide. Your thickness is up to your measurements.
Edited by TERRY - 07 Jan. 2019 at 4:16pm |
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BOULDER 48 2A
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Greaser007
Member Joined: 16 Jan. 2018 Location: Anderson, Calif Status: Offline Points: 850 |
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What is the endplay supposed to be ?
For some reason, I don't think that is enough to cure a second gear issue. My experience, limited, but if you are popping out of 2-nd on decal, you probably need a new 2-nd gear, and / or the locking-ring. the two have a slight reverse-cut on the interlocking teeth, and they can "look" good, but when compared alongside a new-cut, you can see a noticeable difference. I had a 2-nd gear pop-out issue with both a '46 T-90 and a '62 VW Bug. It took a new gear with no shimming from what it was on tear-down. When I tear down my T-90, I will have to watch the Stiver's vids before hand and during. YouTube is sure a helpful tool for us hobbyist's. I will keep an eye on this thread to see what works. |
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NCtoy
Member Joined: 28 Aug. 2005 Location: NC Status: Offline Points: 507 |
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Worked on this some today. I had ordered some shims, so I cut them to slide on the shaft. I ended up using 2 .02” shims. This should give me .040” of shim and leave .013” free play, right in the alleged .012-.018” spec, although I can’t find it in the manual. I turned the spacers so the open ends were opposite each other and tightened up the nut on the back to hold it all together. Up to this point I was thinking I was pretty slick. Then I noticed this:
2 of the 3 plates that go in the synchronizer are missing. I think at this point I’m going to button it up and hope for the best while I accelerate collecting parts to rebuild my spare. Edited by NCtoy - 20 Jan. 2019 at 3:42am |
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Greaser007
Member Joined: 16 Jan. 2018 Location: Anderson, Calif Status: Offline Points: 850 |
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There may lie your problem with 2nd gear. yep
The good thing is - you spotted it ! good eyes. It is so easy to sometimes overlook the obvious. But, your end result on the end-clearance sounds good, in the middle. ( I shimmed a NP435 tight thinking it would loosen-up, and has not in 22 years in my ford pickup ). Makes me think that "looser-is-better", and that probably holds true for exhaust valve guides. Hang in there and be patient. take lots of breaks. I have not rebuilt a T-90 in 24-years, and in that one, I replaced just the second gear to fix the popping-out-of-second on deccel. All else looked good on mock-up. ( assemble 3-times to get it right once ) hahaha Will you be running the sealed bearing on the input drive gear ? Len |
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NCtoy
Member Joined: 28 Aug. 2005 Location: NC Status: Offline Points: 507 |
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I got this back together and filled with oil. Good news! Second gear is working perfectly, no popping out of gear. It’s always been a little slow to shift into second and third, maybe the missing plates are why.
Who knows how long they have been gone or how long I can run without them. After draining the oil out I felt around with a magnet but couldn’t find them. I’m still planning on a replacement sooner than later, but for now it’s working great. Edited by NCtoy - 28 Jan. 2019 at 12:44am |
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M38a1327
Member Joined: 29 Jan. 2019 Location: california Status: Offline Points: 16 |
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Hi, I'm interested in doing this as well. Can you please tell me what shims you used (size, etc) , where you got them and how you went about installing the shims. thanks
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NCtoy
Member Joined: 28 Aug. 2005 Location: NC Status: Offline Points: 507 |
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Before jumping straight to the shims, do some searches on second gear problems. There’s a couple good threads.
Do the stuff in the service bulletin here: http://www.cj3a.info/tech/49-30.pdf That being said, I ordered my shims from McMaster Carr. I ordered stainless steel with a 1 1/2” ID. I think the outside diameter was 2 1/2”, but it’s the only OD they have with that ID. I thought about trimming them down, but the extra OD doesn’t really touch anything. They are very close to the rear of the case, but don’t appear to touch. Besides, they will be covered in gear oil. I had already measured and found the thickness I needed to come up with, but I ordered a few different thicknesses. In my case I wanted about .040” of shim. I ended up using two .020” shims together. I carefully cut an open side in them that would fit right to the mainshaft. For a thicker one I made I used a cutoff wheel, but the thin ones I was able to use a pair of sheet metal snips. I then filed the cuts until there were no sharp edges left, and made sure the cut marks were filed smooth with a very fine file. When I put them on the shaft, I turned the open end opposite of each other, then tightened the mainshaft nut back up. It really wasn’t hard, it just took some careful measuring. Before and after opening one side: |
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M38a1327
Member Joined: 29 Jan. 2019 Location: california Status: Offline Points: 16 |
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sounds good. thanks for the info. I'll give it a try.
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Jesse598
Member Joined: 18 Jan. 2024 Location: CA Status: Offline Points: 1 |
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So after a full removal and re-seal and gaskets on a T90, new synchros and 2/3 clutch it was still pooping out of second gear on decel…. I would just like to thank everyone on this post for the info and the you tube video link. I did the rear access plate removal and loosing the rear nut, shift tower removal and with the help of a friend was able to drive the main shaft forward to expose roughly a .050 gap while working a pick in from the transmission to push the original shim back to the bearing. Many shim kits were online but went to the local Napa and got a snap ring with a 1.28 ID and cut off the end just over center. The snap ring measured almost exactly .050 for thickeness. Buy cutting just over center it snaps on the shaft and even if something ever came loose it can’t fly off. Was able to push it into place with a screwdriver and retighten the output gear. No longer pops out of second with a $1.49 snap ring for a shim. Have been dealing with it for years and wouldn’t have figured it out without all the info. Never posted before but figured I should share if it helps somebody else.
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