View Full Version : Transmission, transfer case, overdrive swap question

08-15-2017, 05:31 PM
Normally I can get by with some YouTube videos and a manual with my Jeep JK, but I need some help on this one. This is my first old car that I'm attempting to work on. I have a 1942 (I think) Willys GPW (I think) with either a '69 or '70 Boss 302 Mustang engine in it.

Question: I currently have a T18 transfer case with Dana adapter, a blown overdrive, and a transmission in pieces in a cardboard box. I have come across a T90 transmission ,M-18 transfer case and warn overdrive with Chevy V-8 adapter all put together. I'm thinking it would be a lot easier to drop that whole system in instead of trying to piece what I have back together. Are these parts compatible? Could I swap the bell housing for the 302 onto the new transfer case?

Joe Brancato
10-26-2017, 09:56 AM
DO NOT INSTALL THE T90 with a V8. The T90 came with the old weaker engines, and will eventually fail under a mildly built V8 that has decent sized tires. If you totally baby it while driving, the T90 might last, but then, might as well go back to a 4 cylinder.

I have a older Gen 1 Chevy V8, and finally wound up installing a T98, with model 18 Transfer case and Warn OD.

Just my 2 cents.

10-26-2017, 11:01 AM
Thanks for the advice! Sounds like I’d be better off buying a beefier transmission that’s ready to install

12-11-2017, 08:40 AM
Same here, someone has put a 302 in my 4x4 wagon ?which Manuel transmission would you all use, I'm thinking t19,?

12-11-2017, 11:21 AM
I concur. If the T90 currently in my wagon needs to be swapped out, I would go with the T19. The extra gear, and more wide range of ratios available would make for a good choice. Plus, then I could keep the transfer case the same, with an option to add overdrive if needed, easily.

12-11-2017, 07:46 PM
Kinda what I was thinking,always good to ask.

12-12-2017, 07:19 AM
The T-19 is damned near bullet proof. When I worked on heavy equipment, we had an 84 F-150 with the 300 I6, with the T19 four speed. That truck went through hell on a daily basis. It pulled a 20' equipment trailer, with a usual load of skid steer loader or smaller back hoes. It was wheel drive, but it blasted through snow and ice all winter long. The transmission was so worn down, that you didn't need the clutch after starting out from a dead stop. It would almost fall into the next gear. I tried to buy the truck after it was retired, but the owner wanted way too much money for a rusted out 1/2 ton truck.

12-12-2017, 02:20 PM
Another ? Will the d18 case hold up to the T19 and a 302, the bad thing is the rear axle is offset to the right side any t case change will have rear axle change also.

12-12-2017, 02:58 PM
The T90 and D18 have held up rather well behind the 350 sbc. The only downside to the D18 is that the input shaft has only one bearing supporting the torque load. There are kits available to beef up your existing T case. Another option is the D20 T cases, out of a later Jeep or I H Scout II. They bolt right up, but you then only have one shift lever. There are kits available to convert a D20 to a traditional two stick also. Novak adapters web sight has all the possible options covered under their research page, with pros and cons explained.

12-12-2017, 07:15 PM
What would be a good rear axel and t case combination for my wills wagon with that late 60s 302 and a T19 transmission.

12-13-2017, 06:59 AM
A question that needs to be answered first, is what do you plan to do with your wagon? Are you wanting it to be a trail rig, or an all out off road over lander unit? I personally want my wagon to be capable of going off the beaten path, to explore the local national forests. I want it to be reliable enough to not be worried about putting my daughter in it to drive around, but capable enough to go anywhere. I plan on keeping the Dana 18, but will most likely do some internal upgrades. The axles will see some internal upgrades also, but the housings will remain the same.

The Dana 44 rear is a good axle in it's own right, with the only real weak spot is the two piece key way rear axle. There are conversion kits that eliminate the two piece to a one piece design.

12-14-2017, 07:11 PM
Is the width the same as factory wills or will it have to be cut.

12-15-2017, 06:27 AM
With only eyeballing, the Wrangler axels look to be the same track width. Wagons run the same axles as the CJs, but the truck version is wider, along with the Wagoneer. The early Broncos may be close to the wagon's dimensions, plus you would get the sought after Ford 9" axle. The bolt pattern for the wheels would be the same also. If the axle is wider, then you could run a wheel with a backspace that would keep you within the wheel wells. More than one way to skin a cat.

12-15-2017, 06:34 PM
:D found one.

12-16-2017, 05:08 AM
Good deal.

12-16-2017, 07:57 PM
Dana 44 int scout 3.73 gear

12-16-2017, 08:24 PM
Lower RPMs than the 5.375.

Open it up and check it out.

There can be unpleasant surprises lurking in there!

12-16-2017, 09:15 PM
Oh yea! I'm going all the way through it, I need it dependable.lots of road trips in my retirement days.

12-17-2017, 05:22 AM
3.73 gears will be a good cruising gear set. Great find! Did you get the front axle also?

12-17-2017, 06:28 PM
Rats, just the rear. And the Dana 20.

12-18-2017, 05:56 AM
Then you are 2/3 the way there. Better than when you started. You could always change out the gear set to 3.73, then you would be 3/3.

12-18-2017, 07:03 PM
It does have a 3.73 gear, I just have get a set for the front.

12-19-2017, 01:49 PM
Yes, I was referring to changing out the front gear set to match the rear. Sorry for the confusion.