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Odd T90 Problem (I think)

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JeepGuyintheBurbs View Drop Down
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    Posted: 14 Sep. 2021 at 8:03pm
Hello everyone. New member, this is my first post. I was hoping as a new memeber this would be a introduction of my drivable CJ2a but I've run into a problem I haven't found using the search functions (advanced, Google, etc.). Maybe my problem and it's solution is somewhere, I just couldn't find it. I've already gotten a lot of other great help and assistence from this site (thank you everyone, your're selfless sharing of knowledge is great and I hope to return the favor by doing the same down the road) but now I'm stumped. When I got my '46 Cj2a it had a 1981 inspection sticker on the windshield and according to the title the owner I bought it from only had it for 3 years and put only 200 miles on it around his small farm. After slowly and gradually working on it I got to the point where I could take it for a short test drive to see what other work it needed. On this short first drive I was able to shift the transmission into first and second gears, and that drive went very well. Let me now say I'm aware that the T90 cannot be speed shifted, and I shifted slowly and carefully. The next day I went a little furthur and this time shifted into 3rd gear. Right after I did this my problem started immediately. The shifter seemed to be stuck sort of around 2nd and 3rd, and I couldn't shift anymore. I got the jeep home and took the top shift assembly off. It seemed to be sticking somewhat so I took it apart, cleaned it and replaced the springs and poppet balls. When I put it back on my problem was unchanged, I still couldn't shift the trans with it at all. I then removed the transmission from the jeep, and when I got it on my bench I discovered that with the exception of the low/reverse gear everything else on that main shaft/main drive gear shaft was stuck. Nothing on that shaft was turning. And unlike the video I've seen where the rebuilder grabs the ends of the main shaft and main drive gear shaft and seperates it into 2 by pulling on it only his hands, mine will not come apart. I removed the joined/stuck shafts   from the transmission case by pressing off the front bearing and tried careful prying and soaking it with penatrants but it won't come apart. The clutch hub for the 2nd and 3rd gears will only move if I hit it with a rubber mallet, it does not move easily. The 3 shift dogs also seem to be stiff, very little movement. I even tried applying mild heat (350 degrees) from a magnetic engine block heater with no effect. I'm guessing that the previous owner had no need to use 3rd gear on his farm, and if the jeep was sitting in storage for a long time before that (which I suspect judging from the good condition of the jeep) I'm the first to put the T90 in 3rd gear in decades. Let me also add that there was no rust inside the transmission when I first opened it. There was transmission fluid in it when I drained it along with only about one ounce of water. No metal in the bottom of the case, no gold flakes floating arouns as a result of incorrect trans fluid having been previously used. I did refill it with GL-1. And the gears appear to be in good shape.  Any suggestions as to what I should do next? I want to continue disassembly so I can evaluate which parts need to be replaced, and I'm assuming some part or parts failed after I shifted into 3rd.   
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TERRY View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TERRY Quote  Post ReplyReply Direct Link To This Post Posted: 14 Sep. 2021 at 8:34pm
Take the shaft out and remove the synchro assembly and reassemble as shown in the shop manual. If the dogs are binding, or the springs worn, replace them.

Edited by TERRY - 14 Sep. 2021 at 8:37pm
BOULDER 48 2A
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JeepGuyintheBurbs View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JeepGuyintheBurbs Quote  Post ReplyReply Direct Link To This Post Posted: 14 Sep. 2021 at 9:03pm
I already have the shaft out of the transmission case. I'm unable to seperate that shaft into 2 parts. I believe I cannot replace the syncro assembly until I get the shaft seperated. Correct?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Joe DeYoung Quote  Post ReplyReply Direct Link To This Post Posted: 14 Sep. 2021 at 11:42pm
Your gears look rusty and pitted to me. They should be replaced if you're planning on using that transmission much.
Joe DeYoung
to many jeeps, parts, and accessories to list here, but apparently enough to keep me in trouble with my wife.





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Post Options Post Options   Thanks (0) Thanks(0)   Quote athawk11 Quote  Post ReplyReply Direct Link To This Post Posted: Yesterday at 12:37am
When pulling the transmission, we are all working hard to keep the main-shaft and input-shaft together.  They basically fall apart if you don't take special precautions to stop it.  If your shafts are stuck together, you probably have pretty severe rust damage to both shafts where the roller bearings ride.  See photo below to see these roller bearings...

 
1- 1946 CJ2A   
2- 1949 CJ3A
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Post Options Post Options   Thanks (0) Thanks(0)   Quote athawk11 Quote  Post ReplyReply Direct Link To This Post Posted: Yesterday at 12:45am
Here is a picture of the main-shaft nose that fits into those roller bearings...

1- 1946 CJ2A   
2- 1949 CJ3A
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bruce W Quote  Post ReplyReply Direct Link To This Post Posted: Yesterday at 1:07am
  I agree with Joe. Also, it looks mighty dry in there. Are you sure there was oil in it? How much?

When in second gear, the input shaft is turning faster than the output shaft. That's when those roller bearings that Tim showed do their work. If they're not lubricated they'll become very hot very soon. Then when the transmission is shifted into third gear, both shafts turn at the same speed, there's no motion keeping the rollers moving, and if they're hot enough, they can weld themselves to both shafts, making all three items one piece. Could this be what happened here?
  If you do manage to get the two shafts pulled apart, I'd bet my lunch that you'll find both shafts and all 14 rollers ruined.
BW
It is NOT a Jeep Willys! It is a Willys jeep.

Happy Trails! Good-bye, Good Luck, and May the Good Lord Take a Likin' to You!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote SE Kansas 46 CJ-2A Quote  Post ReplyReply Direct Link To This Post Posted: 22 hours 4 minutes ago at 9:08am
When I operated my shop, I have taken apart T-90s that the nose of the mainshaft were so worn that there was a ridge holding the roller bearings in place and a matching ridge on the inside of the input shaft. There was enough of a ridge in both shafts that the rollers would fall in the ridges and keep the shafts from separating. The assembly was just loose enough to operate in the lower gears but was misaligned enough to not allow the syncronizer to slide onto the input gear when shifting to 3rd gear.

The abnormal wear was caused by a lack of oil or water in the transmission in most cases. Indeed, in one instance there was probably only a couple of tablespoons of oil in the bottom of the case. That transmission had to have howled like a banshee. That particular transmission was toast as it turned out.

Edited by SE Kansas 46 CJ-2A - 22 hours 3 minutes ago at 9:09am
46 CJ-2A #64462 "Ol' Red" (purchased April 1969)

U.S. Coast Guard Chief Petty Officer (ret.)
U.S. Army Vietnam veteran and damned proud of it.



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JeepGuyintheBurbs View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JeepGuyintheBurbs Quote  Post ReplyReply Direct Link To This Post Posted: 20 hours 18 minutes ago at 10:54am
Thanks for your input, everyone. When I first drained the trans fluid afrer I got the jeep it seemed like it was only half full and the fluid was blackish brown. I've kept it full of GL-1 since but I suspect due to the good overall condition of the jeep and the 1981 inspection sticker on it that is was sitting somewhere unused for decades before the young owner I bought it from got it, and from the looks of it he didn't do anything to it. I have tried PB Blaster and Kroil on the shaft, and had the whole shaft soaking in a container of half ATF and half acetone with no success. Some of the pictures I posted make the gears look rusty and pitted but they're not, I took those pics after I briefly sprayed brake cleaner on the shaft anf that may have caused a little surface flash rust (I used brake cleaner to successfully free up the distributor seized in the block). The brake cleaner did not work either. Thanks for the details on the issues that may seized the 2 shafts together, I suspected some sort of unseen failure was happening. I'll try a little bit more to seperate them but I suspect you're right and all new parts are needed. Oh well, onward and upward.  
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