T-90 Disassembly/ Rebuild, A photo reference

[Doug]

I thought that I would post a photo reference of a T-90 transmission tear down and rebuild for those who may have never done it before to be able to see what is involved or maybe are in the middle of the rebuild and are stuck.

This is not intended to be a how-to, just merely a photo reference of disassembling and rebuild of a T-90 transmission. I used Rick Stiver's T-90 rebuild guide and also his video. The disassembly was not difficult at all; probably takes about a half hour to an hour and the most exotic tools required are a brass drift and hammer and a good pair of flat tip retaining ring pliers.

Here is the first shot where I removed the main drive gear (input shaft) bearing retainer:


After that, I pulled the whole main shaft assembly out of the rear of the transmission; a little finesse is required:


Here is a shot of the lock plate:


And here is a shot after the lock plate was removed:


This is a picture of the front of the transmission and you can see the end of the counter shaft about in the center of the photo:

[Doug]

As you're using your brass drift and hammer to drive the counter shaft out towards the rear:


And here is the counter shaft totally removed. When it is removed, you can hear the counter shaft gear drop a bit into the bottom of the case:


After the counter shaft gear drops into the bottom of the case, the main drive gear (input shaft) should come out from the front of the transmission. Mine had some issues coming out, but I was able to convince it to come on out anyway:


Next, the counter shaft gear can come out of the case. A little finesse is required once again:


Earlier in the disassembly, you may have heard some needle bearings falling, here we can see some parts and pieces laying in the bottom of the case. We also see the reverse idler gear, still in place:

[Doug]

Here is the counter shaft gear with all of it's guts spilled:


I tipped the case on it's end to allow the little extra oil to drain:


Remove main drive gear snap ring:


Now it's time to remove the bearing from the main drive gear. This bearing took a lot of coaxing to come off; it was probably the most difficult part. Holding it like in the picture, you pound down onto a piece of wood or something so as not to damage the end of the main drive gear:


Here, the bearing and oil retaining washer are off of the main drive gear:

[Doug]

Here is the main shaft assembly with all of it's parts and pieces as it came out of the transmission; remove the snap ring:


And, the main shaft assembly in pieces:


Put the case up on it's end on blocks for removal of the reverse idler gear shaft. You'll use your brass drift and hammer again:


Here are the reverse idler gear and shaft out of the case:


Finally, all of the T-90 internals laid out for inspection:

[Doug]

After inspecting parts, cleaning things up and buying your required parts (I needed a small parts kit and a new second gear) you can begin reassembling your transmission.


Starting out with the bearing washer and bearing on the main drive gear:


After using a brass drift and hammer to seat the bearing, install the snap ring:


Main drive gear ready for installation into case:


Dowel rod in center of counter shaft gear. Here is where you will use the special tools as described in Rick's guide. It makes installing the needle bearings a snap. You may want to cut the dowel rod a bit longer, just enough that it will hold the thrust washers in place on either end of the counter shaft gear during installation.


The first set of bearings installed quickly and easily. The only problem that I had is that the dowel rod was just a bit too fat. I took it out, sanded it down and it worked fine after that:

[Doug]

Fully loaded counter shaft gear with thrust washer installed:


I used a short dowel and the old reverse idler shaft and slid them in from each end just enough to keep the thrust washers in place against the case while sliding the counter shaft gear into place. I greased the thrust washers and it helped hold them in place while installing the counter shaft gear. If you made the dowel rod a bit longer as described above, that will work as well.


Install the main drive gear from the front of the case and then install the counter shaft:


Reverse idler gear in place:


Install reverse idler shaft making sure that the slots in both shafts are lined up for the locking plate:

[Doug]

Clutch hub/ sleeve put together along with new blocking rings:


Here is the brand new second gear and the clutch hub/ sleeve assembly installed onto the main shaft:


Installing bearings into the main drive gear:


Main shaft installed into case:


Sliding gear installed onto main shaft:

[Doug]

Rear bearing adapter installed:


Rear bearing installed:


Felt oil seal in place:


Locking plate installed. It is important to note that the locking plate cannot extend below the shafts. If this is allowed to happen, the transmission likely will not mate properly to the transfer case.


Main shaft gear/ washer/ nut installed temporarily just so they don't get lost:

[Doug]

Finished T-90 transmission, ready for installation and a test drive (almost, anyway):


One thing that I think I would do differently next time would be to install the locking plate BEFORE the rear bearing. It would give more room.

Other than a new small parts kit, I bought a new counter shaft, reverse idler shaft, reverse idler gear, second gear and blocking rings.

I hope this is of some help to someone

[Jon]

Nice job with the illustrations Doug, Its amazing how the T-90 and the D-18 (and other models) almost look like they shared the same engineers at that time. The principals and components look like they can almost be interchanged. They performed all that technology with out CAD and C&C machines. Jon

[KitC]

Doug, Thanks for posting the pictures...I may have to give it a try after all.