T84 to T90 conversion

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
Paul Randazzo
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T84 to T90 conversion

Post by Paul Randazzo » Sun Apr 14, 2019 8:15 am

Hello all,
I’m in the process of restoring a ‘42 MB. The Jeep had a T90 and Spicer 18 t-case installed some time in it’s life but was done incorrectly. The engine, trans and t-case were barely bolted in, (basically just laying in the vehicle) not making any accommodation or modifications for the extended length of the T90. The owner is keeping the T90 setup. We will make all the accomodations/modifications needed for the vehicle to accept the T90 conversion. Now the question. Which cross member do we need to make this conversion work? The difference between a T84 crossmember and T90 are different in the height of the offset, allowing the trans and t-case to sit lower in the frame while maintaining the correct engine/trans angle. The other problem is that the t-case insulator does not meet up with the “tab” on the front bearing cap where it attaches (about a 1” gap). We are not going to modify the crossmember to chassis brackets to accomodate the T90 (we don’t take short cuts). We will however move the brackets aft to make up for the difference in length of the T90. We already got the correct drive shafts e-brake, speedo cable and linkages needed for the conversion. A CJ crossmember has a different mounting at the ends where it attaches to the chassis. I think I gave all the information needed. Any answers welcome. Thanks guys.
Paul
1960 Hotchkiss M201
1951 JDF 1/4 ton
Fleet Automotive Tech ret
Chief Veh Maint Mech Museum of American Armor Old Bethpage NY

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JAB
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Re: T84 to T90 conversion

Post by JAB » Sun Apr 14, 2019 6:28 pm

Paul, I'm trying to go by memory, but I had a '45 GPW (sold it over 20 years ago) that had a T-90 grafted into it. The floor was barely cut (I think a CJ floor cover hid the one area that was cut) and if I recall the crossmember was the original GPW crossmember. The CJ floor cover is bumped up, allowing the T-90 to fit under it where the GPW cover is flat. I think the mounting plate (isolator I think it's called in the manual) was modified somehow. I remember that the transfer case snubber mount had a thick bracket extending it so that the snubber fit the transfer mount.
You might have better luck in the modification section with this post, as keeping the T-90 is considered a modification and contradicts the description of "restored" for most people here.
-Jeff

GR8GPN2U!!!

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Paul Randazzo
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Re: T84 to T90 conversion

Post by Paul Randazzo » Sun Apr 14, 2019 7:06 pm

Hey thanks Jeff. I believe there was an early 2a crossmember that was in a 2a that was part MB from the factory, you know the ones built from left over MB parts. I’ll copy this post to the modification section. Again thanks for the reply
Paul
1960 Hotchkiss M201
1951 JDF 1/4 ton
Fleet Automotive Tech ret
Chief Veh Maint Mech Museum of American Armor Old Bethpage NY

OldPappy
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Re: T84 to T90 conversion

Post by OldPappy » Sun Apr 14, 2019 7:07 pm

This is a very common conversion.

To do it right, you need a CJ2A cross member, which sets the transmission a little lower, and the cross member is mounted about 2" toward the stern of the vehicle. You also will need to cut the floor plate to accept the T-90 shifter, and use a CJ2A cover to cover the hole.

I am doing the same thing with my current project, and have done it several times in the past. It is a piece of cake, and if your Jeep is intended as a driver instead of a show car, this modification is an improvement.
A.C.Fults
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Re: T84 to T90 conversion

Post by IvorGPW » Sun Apr 14, 2019 7:11 pm

I have a T90 in my daily driver MB. As far as modifications go the floor has been cut back and a new hole where the transfer case mounts has been drilled farther back. The clutch linkage has also been extended.
Tate Christensen
1944 Ford GPW #234613 USMC Radio jeep
1943 Willys MB #263100
1945 Willys CJ2A #10226
1941 Ford GP #9687


Paul Randazzo
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Re: T84 to T90 conversion

Post by Paul Randazzo » Mon Apr 15, 2019 6:00 am

Thank you gentlemen. Doesn’t the cj crossmember attach differently to the frame?
1960 Hotchkiss M201
1951 JDF 1/4 ton
Fleet Automotive Tech ret
Chief Veh Maint Mech Museum of American Armor Old Bethpage NY

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Re: T84 to T90 conversion

Post by Bruce W » Mon Apr 15, 2019 11:07 am

Paul Randazzo wrote:
Mon Apr 15, 2019 6:00 am
Thank you gentlemen. Doesn’t the cj crossmember attach differently to the frame?
For the most CJ2-A's, no. The CJ3A had a different crossmember that attached in a different way, and some very late CJ2-A's used the 3A-style crossmember. Most CJ2-A's had a crossmember that attached the same way as the MB/GPW, but a bit further to the rear. BW
G Trp 2nd Sqdrn 3d Armored Cavalry Ft. Lewis 1970-71. 43GPW(Sarge?) 47CJ2A(Teddy) 47CJ2A(Rusty) 48CJ2A(Uncle Linden) 53CJ3B(Nelybel) 88XJ(Pluto) NE CO

Paul Randazzo
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Re: T84 to T90 conversion

Post by Paul Randazzo » Mon Apr 15, 2019 1:14 pm

Thanks again for all of your help and ideas. I located the exact crossmember I needed, an early CJ with the mounting like the MB.
1960 Hotchkiss M201
1951 JDF 1/4 ton
Fleet Automotive Tech ret
Chief Veh Maint Mech Museum of American Armor Old Bethpage NY

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Tony W
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Re: T84 to T90 conversion

Post by Tony W » Mon Apr 15, 2019 9:04 pm

Hey Paul
Heres a few pics of my T90 conversion. Very solid gearbox, much stronger than T84. Super simple to rebuild and parts quite cheap.Image
Image
Image
Image
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Hope these help with the conversion.
Good luck
Tony
GPW Feb, 45,
chassis 259112
body 214625
engine MB131277 Overstamped XXX4B1945
ARN 153851

Paul Randazzo
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Re: T84 to T90 conversion

Post by Paul Randazzo » Tue Apr 16, 2019 6:09 am

Hey Tony
Great job, great reference, great photos, great lookin' Jeep. I see a 3A bell housing too. What ever works. It all worked out nicely. Did you lower the cross member for clearance of the transmission cover and floor? Just watch your head on the old crossmember mounts when you go under the Jeep! Ouch!! I'll post photos when we get it together.
Paul
1960 Hotchkiss M201
1951 JDF 1/4 ton
Fleet Automotive Tech ret
Chief Veh Maint Mech Museum of American Armor Old Bethpage NY

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Re: T84 to T90 conversion

Post by northcoastsailor » Tue Apr 16, 2019 10:40 am

I made the same conversion as Tony W. for the rear crossmember by using the 3A style. I haven't used any spacers yet; wondering if I will have to once the body goes on...

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I had bought the jeep already with a CJ motor and T90 in it, and knew I wasn't too worried with originality issues concerning the use of a T90. The conversion by the previous owner, however, was a mess. Basically they took the original T84 crossmember bracket, and welded on extensions at an angle to get the T90 transmission to sit further back. My goal was to clean this up and make it at least look correct and not some back woods fab job.

Image

Note in the first photos, that the new crossmember sits further back. If you do try and use the CJ2A member, you will have to devise a method of moving the mounting bracket aft ~1.5". I found the 3A crossmember to be the least intrusive with new holes, especially if I ever got the bug to put in a T84. I need to get some brackets made up to go in place of the original crossmember brackets in order to mount the tub and the return spring.
GP-MB-2A "Old Crow" (Mostly MB 432554)

Paul Randazzo
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Re: T84 to T90 conversion

Post by Paul Randazzo » Tue Apr 16, 2019 1:32 pm

This Jeep had L134 with a T90 and a Spicer 18 from a pick up truck. No parking brake arrangenent on this model 18 (had to source those parts). The engine, trans/t case were basicly just laying in the vehicle. Only one motor mount attaching it to the frame. The engine was seized beyond repair. The oil pickup had broken off and fallen into the pan. The trans needed a total rebuild and the t-case needed all new bearings. We replaced the bearings in the rear diff. The gears were so worn that we couldn’t get a good wear pattern or back lash, not to mention the spider and side gears were so worn from slipping one wheel all the time. We ended up swapping out the whole diff, replaced the bearings checking the wear pattern and back lash then we were good to go. I’ll send photos later. BTW your photos did not come through.
Paul
1960 Hotchkiss M201
1951 JDF 1/4 ton
Fleet Automotive Tech ret
Chief Veh Maint Mech Museum of American Armor Old Bethpage NY

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Tony W
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Re: T84 to T90 conversion

Post by Tony W » Sat Apr 27, 2019 12:37 am

Hey Paul
Sorry about the late reply. I have just spent the last 2 weeks camped on a beach down south in WA. No phone or internet coverage, we were camped 50 klms off the bitumen down a sand and mud track. Bliss.
As to the question of spacers, yes you will need to drop the cross member or the box will hit the body, and will not go on. And you need to level the engine a bit. The T90 is a lot taller box. Mine is dropped about an inch or slightly less.
Any questions or pics, don't hesitate to ask.
Tony
GPW Feb, 45,
chassis 259112
body 214625
engine MB131277 Overstamped XXX4B1945
ARN 153851

Paul Randazzo
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Re: T84 to T90 conversion

Post by Paul Randazzo » Sun Apr 28, 2019 4:57 pm

Tony,
Happy to hear you had a great camping trip! As for fitting the body we’ll see what that will take. We sourced an early 2a crossmember. We wanted to keep with the original mounts, we’ll also deal with the body mounts that mount on the crossmember brackets. We’re using 2a stay cable, clutch linkage, e-brake and speedo cables. Tell me about your custom adjustable clutch linkage. Here are some photos.
Paul
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1960 Hotchkiss M201
1951 JDF 1/4 ton
Fleet Automotive Tech ret
Chief Veh Maint Mech Museum of American Armor Old Bethpage NY

northcoastsailor
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Re: T84 to T90 conversion

Post by northcoastsailor » Mon Apr 29, 2019 9:20 am

Photos should work now. I'm hosting them on Google, and had some issues with them not showing when not signed in. Updated the sharing parameters so hopefully that's fixed.
GP-MB-2A "Old Crow" (Mostly MB 432554)

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