T90 Rebuild

Hello All,

Past weekend I went on the longest ride yet after installing new exhaust system... A couple times when decelerating I slipped out of second gear.... Does anyone have a good idea or estimate how much it will cost to rebuild (from a shop)? I understand you don't really know until you get in there, but I'm just looking for a range...

Thank you


Edited by ggordon49 - 28 Sep. 2017 at 3:35pm

thank you, sir.... Is this something you guys feel can be done successfully by a novice? I'm confident in my abilities but I have never rebuilt one before... In my experience, some things should be left to someone who knows what they are doing... I'm not a complete moron, but I'm not a professional either

There are some good step by step guides out there and if you were ever to start on working on a transmission, the T90 is the one to start on. Pretty simple for the most part. 

ggordon, I feel your pain, I drove my 47 willys on the FCT 17 this year and experienced the same situation with slipping out of second gear. After talking with some of the old hands there at the FCT it seems that it is a common problem with the T-90. I got several opinions as to the cost to send my T-90 away for rebuild or exchange, estimates ran from $750 to $1100. All of the old hands also said that a DIY is not that difficult with a minimum of mechanical aptitude. With the help of the forum here and all of the online info available I plan to remove and rebuild my transmission this winter. Good luck, I'll watch your posts to see how you are proceeding!      

The T-90 is about as easy a rebuild as any transmission. It was the first transmission I ever rebuilt and that was almost 50 years and literally hundreds of transmissions ago.

A few simple things to consider:

During disassembly keep all the parts...whether you think they are bad or not and keep then in an area that is devoted to just that job. In my shop all transmission teardown parts went into metal draon pans...nuts bolts, everything. Nothing got thrown in the scrap until the transmission was back in service.

Always replace all gaskets and seals. Bearings are suspect and subject to replacement in most instances. If the object of the rebuild is to keep the transmission in service without problems, then the price of the replacement bearings shouldn't be a factor.

Unless you have done several of the same model transmission, follow the service manuals for that particular transmission. It does not hurt to look at several manuals, because the writer of the manuals may often overlook a particular procedure because they assume you might already know that procedure and plan to use it. As mbullism points out, he has read manuals that cover about 95% of the job. Reading several gives the first time rebuilder an excellent overview of the entire operation.

Inspect each gear and shaft for undue wear. Pay particular attention to the clutch teeth (synchronizer teeth) on the main drive gear (input gear) and the mainshaft second gear. They should not have rounded points on the clutch face of the gear. Always use new synchronizer stop rings, but you should really consider replacing the whole synchronizer assembly because the three dogs in the synchronizer can be worn and not show it. Attention should be paid also to the mainshaft 1st-reverse sliding gear. This gear often gets a workout when the driver attempts to downshift into first gear without coming to a full stop. The gear teeth should not have any chips out of the teeth. The countershaft gear (cluster gear) needs to be inspected for the same damage as the 1st-reverse gear. The reverse idler gear needs inspection at the teeth and the bushing inside the gear; it should turn smoothly on the idler shaft and no detectable wobble on the shaft should be detectable.

The transmission should be thoroughly cleaned inside and out. The front bearing retainer should be inspected for wear where the clutch throwout bearing slides on it.

An inspection of the shift tower should be made. The shift forks where they engage the gears shouldn't have excessive wear and should be solidly mounted on the shift rails. This is a little more forgiving than the rest of the overhaul in that if something isn't quite right with the shift tower at least it can be removed easily in the event that something needs to be corrected.

There are some options on the T-90 main drive gear (input gear) that need to be considered. These have to do with the type of seal used in the front of the transmission. The original seal was a layered felt-rubber seal that sealed against the back side of the front bearing retainer and is prone to leaking after being in service for a while. Other designs include a new style retainer with a conventional seal in place and a still different solution using a sealed bearing in place of a input seal. There are pros and cons for each method but you do need to be aware that there are different ways of solving the front seal leakage problem that can be prevalent in T-90 transmissions.

Use only top quality parts from a reputable supplier. Avoid using used parts, especially bearings with a questionable history.

The most complicated part of rebuilding the T-90 is the mainshaft spacing...it must be right, but we are here to help when you get to that step.

Finally, don't be afraid to tackle this job yourself. With the proper service literature, patience, good shop practices, and the help you find on this forum you should be able to rebuild the T-90. Many of us on this forum have rebuilt the T-90 and can help you if you have questions. Just ask on this thread, and we will give you the help you need.

You can do it...

I'm in the thick of rebuilding a t90 for the first time myself. And I know nothing. You can do this. Google Rick Strivers videos. They are excellent.

that sounds like a great deal.

Now take this comment with a grain of salt.  I too was where you are.  I have NEVER EVER worked on a car before.  Got my CJ2 and it needed the trans redone.  With the help of the gang here on the board and one member who actually had me over to his house to use his tools and time to show me how to do it - IT DID IT!  Of course it wasn't right!  The "great videos" neglected to mention you have to measure the endplay on the mainshaft and you have to get that right otherwise it will fall out of second downhill.

92889 wrote: I'm in the thick of rebuilding a t90 for the first time myself. And I know nothing. You can do this. Google Rick Strivers videos. They are excellent. https://www.thecj2apage.com/forums/42-47-rebuild-project-in-tsawwassen_topic36802_page6.html

Thanks for the support and info! Appreciate it.