Perfect T-84 to T-90 Conversion

[Fred-D]

This is lots of work but there is NO cuting of the tub. First I cut those humps of of the top of the Tans. cover. Machined flat and pluged the holes. Bored holes in from the side, Taped With a 5/8 fine tap, made new spring tubes, screwed in place, sealed with JB weld and pined in place with 6-32 screws. That gave me 3/4 inch. Then used m38 cross member, drive shafts and linkage. Had to reposition linkage tube suport to the rear and down. Used same motor mount that is used in front at the rear except used it upside down. then put tans. incontact with cross member Oh don't forget to cut that O-ring off the cross member. Used two sets of transfer case levers, cut the tops off one set the bottoms off the other. Then welded them together 1 and 1/4 inches apart. So they would line up with hole in tub. Fabricated a new floor plate with shifter tower hole in the right place. And used 2 shifter boots, cut the top out of one the botom out of the other slid them over each other to cver shifer tower. Use CJ top cvers for conversion NOT m38. It does take a milling machine to do the machine work. I had to slitely dimple the firewall to clear the throttle linkage but is not noticeable. it was a lot of work but you can't see the mods form the top side. I had to do this because I will have some of my friends driving it, without having Expireance they will tearup a t84.

[Hobo]

Fred,

good job! But, I can not understand how one can break a T-84????

I am used to clutch and shifting, but since 18 years I drive an automatic for daily rides...still, the Jeep is no challenge, really! Is it not only the first gear which should be engaged only when stoped? All others synchronised...

[Fred-D]

Hi Hobo
I have several friends that have Jeeps and the only complaint they have is the T84. My first GPW already had a T90 in it and all I did is clean up the installation. and got all the way to those two little humps Now I am building one from the ground up and want it to look rite and be as trouble free as possible

[Bob N]

Well, they only way I managed to tear up my T-84 was to run it with either the wrong gear lube or too little lube...anyway I suspect damage due to heat and subsequent gear failure, shearing of teeth. Managed to destroy about a 1/3 of the cluster gear. But the dam n thing still drove fine! It was just noisey, experts here said, "don't worry about it--they are all noisey". It wasn't until I tore it down and discovered WHY it was so nosey. After I replaced all the gears in the box, bearings, etc, it is quiet as a mouse. I'm being more diligent about checking the lube level!

Also, not running a lube other than 80 or 90wt depending on the time of year (or 80/90) is important. Some folks thing that running a 140 will solve their leak problems (as if). But all this does is generate more heat...heat breaks down the lube and can lead to gear failure. Just like they think running 20w50 is good for their engines...it is if you need more heat in the engine surfaces...there's this crazy math formula I got from some automotive engineers on an engineering site that helps illustrate this. I hope to send the MVPA something they can use in an article that will discuss oil. BTW the same things were said during WW2 (Army Motors)...use the oil grade specified by the MFG.

[Fred-D]

Finely figured out the camera and how to post pictures

http://jeepstuff.mypicgallery.com

I will try and get more detailed pictures later

[Bob N]

Interesting pictures. How were you able to keep the clutch pivot tube straight or is it crooked, I couldn't tell.

[Fred-D]

Hi Bob N

I relocated the frame braket 1 1/4 inch further back and 3/4 lower on the frame

[MAJ Tim]

My GPW has a T90 in it...and it likes to rattle and pop out of second gear. It's a real pain. I understand it is likely the synchronizer that is the problem. I was looking in a catalogue today and saw I could buy a new T-90 syncrhonizer for $50....how difficult is this to replace in order to fix the problem.

MAJ Tim

[Bob N]

You can check out some of the later jeeps for exact instructions but I think you will find it to be a realatively simple manner. But as long as you have it apart you might as well rebuild it...checking all the parts, the stick shift for wear, etc. I would replace the main bearings at at least the small parts kit. Rebuilding the T-84J was "easy", the T90 couldn't be that much more difficult.

[Fred-D]

Added more pics


http://jeepstuff.mypicgallery.com

[lindyp38]

im new to all this....

what is the advantage of having this mod....

thanks

[Herb Tate]

I have seen Fred's conversion in person and it looks great!! I was very impressed how "stock" it looked.