Joined: Jan 31, 2017 Posts: 72 Location: Salt Lake City, UT
Posted: Fri Feb 03, 2017 10:57 am Post subject: 1952 M38 - T-90 transmission rebuild
Hey guys, just picked up a1952 M38 and am looking at getting it back up and running as it should be. Currently it sorta runs, well enough to take a loop around the ranch I bought it from. During that test loop, I noticed that it would transmission would slip out of 2nd gear quite easy. Based on my limited knowledge on transmissions (generally I have someone else do transmission work), my guess is that the 2nd gear synchro ring is worn and needs to be replaced.
It's about time for me to put my big boy pants on and rebuild a transmission myself but I hear horror stories about people using knockoff/cheaper parts and having things go wrong. So, my question is, does anyone know of a good quality rebuild kit for a T-90 transmission? So far it seems like Novak Conversions kit is the best but I can't say for sure since I'm brand new to this.
Any advice would be much appreciated! Thanks everyone.
Joined: Feb 09, 2014 Posts: 178 Location: Tri Cities, Washington
Posted: Fri Feb 03, 2017 11:39 am Post subject:
I rebuilt mine with Novak, I think one reason they pop out of 2nd is the shifting forks are worn also. Novak didn't have any shifting forks the last time I called them. There is also a video on YouTube that is a step by step rebuild tutorial on the t90 and Spicer 18 TC. You might be interested in taking a look. Good luck. _________________ Rusty, 1952 M38, Koenig hard top.
Joined: Jan 31, 2017 Posts: 72 Location: Salt Lake City, UT
Posted: Fri Feb 03, 2017 1:04 pm Post subject:
I have watched 3 or 4 different YouTube videos on how to rebuild the T-90 which is why I think I can handle it on my own. Nothing like a home made YouTube video to inspire some confidence!
Did you end up using the existing shifting forks or did you buy them from another vendor?
Joined: Feb 09, 2014 Posts: 178 Location: Tri Cities, Washington
Posted: Fri Feb 03, 2017 1:28 pm Post subject:
I still have the original forks. It just pops out about 30% of the time. Just enough to drive me nuts. I've been looking around, just not as seriously as I probably should be. I'd like to get some forks from someplace reputable. _________________ Rusty, 1952 M38, Koenig hard top.
Joined: May 30, 2014 Posts: 3447 Location: Texas Hill Country
Posted: Fri Feb 03, 2017 1:52 pm Post subject:
Rusty,
I'm in the middle of that same project.
You say it jumps out of 2nd gear because of worn shift forks.
Do you mean the forks being worn or the poppet balls and springs
needing replacement?
I'm looking at my shift tower and it seems those forks would have to
be really ground down to allow the gear to come out. The pins could be really be really worn.
Walker,
I have nearly completed putting my T90 back together and have rebuilt
the shift tower. It's all or none. Worn parts in either can cause you grief.
Granted, I don't have everything back together yet but it isn't brain surgery.
Rick Stivers has a rebuild guide on line and I have it, along with Moses Ludel's
book as well as the TM's near the workbench. All of the military manuals
are available here free for downloading.
I have and continue to receive good advice from friends here on the board.
The recommendations regarding parts are to buy from vendors sourcing
NOS new old stock parts, surplus military stocks, and in the case of bearings if
new US bearings are not available then Japan. Do not buy bearings or shafts in particular made in China.
Reputable suppliers that carry NOS or US made parts (And Japan bearings)
are Peter DeBella, Brent Mullins, Army Jeep Parts, Midwest Military and Ron
Fitzpatrick. You need to make a list of parts then have an over the phone conversation with one or more of these vendors and let them know what you
are doing, and that you want NOS or US products.
There are pages and pages of posts here regarding rebuilding the T90 and
D18. Use the search function up top.
One quick and dirty way to get a look is to pull the shift tower cover
plate, make sure the jeep is blocked, put the tranny in neutral and remove
the shift tower. You can turn it over and look for wear and wiggle the forks
to check for excessive looseness.
Joined: Jan 31, 2017 Posts: 72 Location: Salt Lake City, UT
Posted: Fri Feb 03, 2017 4:51 pm Post subject:
Right on, thats the kind of stuff I was wanting to know. I'll be on the look out for NOS/US made parts. I knew about the China stuff, just wanted to know if anyone had some vendors that they would recommend. I'll check out the names you gave and see what damage I can do!
I'll post some pics along the way or how this goes. Could be hysterical or successful!
Joined: Feb 09, 2014 Posts: 178 Location: Tri Cities, Washington
Posted: Fri Feb 03, 2017 5:13 pm Post subject:
I did a lot of reading and some of the problems is not getting quality steel to make the shafts. Novak says they have quality stuff and others have used their master rebuild kits too with good results. As for the poppet balls, I did replace the springs and poppet balls. In the tutorial the gentleman gives a clearance of, and don't quote me, but I think 12 thousands of an inch between the forks and the part the forks ride on. What this means to me is when you shift into 2nd gear, your not actually getting it in all the way. I replaced every part in the t90 and Spicer18, except the shifting forks. There is a guy down the road here that collects a wide arrangement of WW2 trucks, jeeps, ducks,Etc. and he told me more than likely it's the forks. This makes some sense because this part gets used just like the rest of the Tranny. I'm not sure what else it could be. But I'm always open to opinions and others experience.
Cheers. _________________ Rusty, 1952 M38, Koenig hard top.
Joined: May 30, 2014 Posts: 3447 Location: Texas Hill Country
Posted: Fri Feb 03, 2017 5:52 pm Post subject:
I would check the pins that hold the forks on the rails. The pins can get
really worn and cause the forks to wobble on the shafts. Easy to replace with new roll pins and safety wire.
The other place is the squareness of the fork notches and the shifter cane. It would have had to take some real abuse for them to be very bad.
Rick Stivers' guide gives a tear down, checkout and rebuild for the shift tower.
It's worth a look. One last place is to check the rails themselves. A guy on Rick's page found a groove worn in the shift rail where the ball rode.
Joined: May 14, 2009 Posts: 971 Location: South Dakota
Posted: Fri Feb 03, 2017 6:00 pm Post subject:
Advice: do not buy Omix Ada parts or made in India parts. The vendors mentioned know what the good stuff is. It's worth paying extra. As to popping out of 2nd gear, The list of causes is long. You need to make anything and everything that's suspect new. What I've gleaned: too much mainshaft endfloat, worn mainshaft where 2nd gear rides, worn 2nd gear , out of spec 2nd gear bushing, worn blocking rings, worn synchro collar, weak poppet ball springs, worn shift forks. Measure the items and check against correct sizes. Add shims if needed, or a new mainshaft spacer. Assemble the thing with the transfercase bolted up and check your endfloat. All the small 1000's of wear add up to endfloat. The drive dogs on the gears if tapered or chipped mean replace the gear. If they are bad, the synchro collar will most likely be bad. Your case thrust surfaces if scored and ground mean you need a new case. If you can turn it by hand, the tightness of the endfloat is fine. I had a tranny shop make a smaller mainshaft spacer because he though it needed .020 endfloat. WRONG!!!!!! get it as tight as you can and still turn it by hand. The bearings alone give enough. I've learned the hard way. John
Joined: Jan 31, 2017 Posts: 72 Location: Salt Lake City, UT
Posted: Thu Feb 23, 2017 3:27 pm Post subject:
Thanks everyone for the input. I'm going to go ahead and go with the Novak kit as it really does seem most everyone uses/likes them.
The next question though seems to have a 50/50 split on opinion. I'm interested in being able to put the jep into 2wd low (both levers forward). With everything I have read, it seems that it is as simple as leaving the poppet ball out during the rebuild. However, half the people think you will destroy your axle with all the torque while the other half says its totally fine. Anyone done this to their jep? Have any horror stories?
I'm wanting to be able to stay in low gear but 2wd to make sharp turns on a trail. A lot of the local trails around here have sharp switchback style turns with enough rocks/debris that you want a low gear.
Joined: May 14, 2009 Posts: 971 Location: South Dakota
Posted: Thu Feb 23, 2017 4:17 pm Post subject:
It's called the interlock pin. Not poppet ball. You have to remove the front output cover to expose and remove it. Guys with locking differentials like it out since they can shift in and out of 4 wheel drive in order to steer when turning with torque applied to the front axle. It also is good for parades in two wheel drive. John
Joined: Jan 31, 2017 Posts: 72 Location: Salt Lake City, UT
Posted: Thu Feb 23, 2017 4:22 pm Post subject:
Thanks for the clarification on the part in question.
Sounds like you are a believer that with the understanding that you aren't going to be using 2wd 4x4 other than simple things like turning, parade runs, etc., I should be safe in leaving it out.
Joined: Jan 31, 2017 Posts: 72 Location: Salt Lake City, UT
Posted: Thu Feb 23, 2017 4:27 pm Post subject:
Yes. Again, thank you for the clarification. Joys of being the new guy trying to regurgitate information I have been reading about. I have a form explaining how to pull the pin and yes, it is from the transfer case. They just say it is easiest to do it while your transmission is out which is why I'm asking about it in this thread.
John listed all but one cause of jumping out of 2nd and it's a cause that should never be overlooked unless you enjoy removing and installing the gear boxes a lot. Worn pilot shaft bushing in the flywheel! As a safe rule always change it when a tranny is removed for any reason.
Oil Leaker said:
Quote:
The list of causes is long. You need to make anything and everything that's suspect new. What I've gleaned: too much mainshaft endfloat, worn mainshaft where 2nd gear rides, worn 2nd gear , out of spec 2nd gear bushing, worn blocking rings, worn synchro collar, weak poppet ball springs, worn shift forks.
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