Lowering a T90 gearbox

[2305johnt]

Hi

We have a T90 gearbox in a 1943 GPW - I have been told that it can be lowered so that the bulge in the hump wont be noticeable? Any truth in this?

Thanks

[Bruce W]

I suppose you can, in fact it has been done, but it will affect a lot of other things as well, most of which you do not want.
BW

[dpcd67]

Sure you just put a spacer between the transfer case cross member and the frame and lower it one inch; it will work fine. Of course the guys here will still tell you to get a T84 and not touch a T90 Transmission in a WW2 jeep. You are limited by how low you can go because at about 3 inches your engine head will hit your firewall and you will know to stop. It will stop itself. Added benefit; it will actually improve your drive shaft angles. I ain't saying do it, or not do it. Just that it can be done. Not sure what negative effects BW means.

[W. Winget]

I'd be more interested in just WHY the T90 has to have such a high tower, and if you could perhaps slice a cross section out and reweld the piece, shortening the stalk as well to still achieve shifting. Have to look at both setups side by side, perhaps I will look at one in the scrap pile, but not soon enough for your answer.
Just a different approach possibly.
V/R W Winget

[dpcd67]

It ain't the shift tower that is the problem; (that can stick up through the hole in the floor plate) the T90 just sits higher because it is a real transmission instead of a toy that the T84 is, which is why it has the higher sheet metal hump, that is not needed on the WW2 jeeps which have the flat cover. It is in the way the shift mechanism is made and works; the 84 has that flat plate while the 90 shift mechanism is taller and takes up more space because the shift rails are actually in the top cover instead of the case body.
So, shortening the tower and shift cane, won't help.
viewtopic.php?t=306509

[dpcd67]

Read these two threads and you will see how they stack up; the T90 is just made higher.
viewtopic.php?t=306509https://forums.g5 ... hp?t=92427

[dpcd67]

viewtopic.php?t=92427

[2305johnt]

Thanks everybody for your replies. Sure would like to replace it with a T84 but in the Uk hard to get and very expensive. To be fair I understand the T90 was better and it runs fine so possibly we should stick with what we have!

[dpcd67]

Of course the T90 is a far better designed and built transmission; there is a reason it was the first change made on post war jeeps and used in jeeps and other vehicles into the 1970s at least. The T84 was selected because it was light and available; not because it was tough.
Build and drive your jeep.

[bazza1946]

It also depends on what your jeep is going to be used for.
If you're going to use it to go on off road trips regularly, rock climbing hard trips, big mileage journeys, you may find the T-90 is more suitable. But if you're only going to use it for display days, or fun runs, concours, driving to the shopping centre, etc, you'll find the T84 will be perfectly usable and strong enough for the job.
And if it's going to be a 'trailer queen', there's no doubt which trans you should use.

[dpcd67]

First post I see; welcome to to forum!
He said he can't get a T84 so will have to use the 90.

[tamnalan]

If my MB had come to me with a T90, I'd be strongly tempted to leave it as-is unless I wanted to do a faithful restoration. It is a much stronger (and heavier) unit, and one can swap in the T90C gears for a little better crawl ratio.

[dinof]

I know a teenager that had a T-90 with a chevy V8, and tormented that transmission via
street racing. It took the abuse very well.

[JAB]

I had a GPW with a T90 and the PO solved the issue by installing a CJ transmission cover instead of the flat floor cover. If I recall correctly the rear of the opening in the floor was cut at each corner and the metal pulled up to clear the rear of the T90 and a few holes were drilled in the GPW floor to accept self tapping sheet metal screws in the places where the holes didn't line up.

[dpcd67]

Yep, that is a way to make them fit if you don't want to drop it I mean lower it.