alternatives to the T84?

1941 - 1945, MB, GPW modifications, sugestions, and ideas, official MWO's and unofficial WWII field mods NO EBAY or COMMERCIAL SALES.
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mboardman
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alternatives to the T84?

Post by mboardman » Thu Jul 22, 2021 5:44 am

Wondering out loud if anyone has substituted a transmission from any other car or tractor and had a more reliable jeep in the end? Any success using say a box from a small modern truck? My floor is rusted out anyway and nothing will be correct on this jeep, so Im fine with making room for a larger unit, if reliable. Just a shot in the dark here. I recall reading once, a long time ago, that a common modification was to attach an overdrive unit from a late 1990s Saturn, and this would give the jeep enough gearing to get up to highway speed? I guess that got me wondering if the T84 could be replaced entirely? Anyone hear of that being done? I really dont care to mess with the T84 any more...
42 GPW 78812*(dod 11/16/42)
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1951 dunbar kapple trailer # 01172524


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Re: alternatives to the T84?

Post by W. Winget » Thu Jul 22, 2021 8:45 am

I can only think the mods I have seen were to upgrade to a T-90.
(edit: I retracted everything, it was funny to me about reliability, but this is the "modification" section, so no offence meant.)
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Last edited by W. Winget on Thu Jul 22, 2021 4:47 pm, edited 1 time in total.
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Re: alternatives to the T84?

Post by mboardman » Thu Jul 22, 2021 8:48 am

This is all obvious to all of us. No real need to say it. Not like I dont already know it.

Anyone have a helpful reply?
42 GPW 78812*(dod 11/16/42)
Willys trailer # 33768
1951 dunbar kapple trailer # 01172524

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Re: alternatives to the T84?

Post by IvorGPW » Thu Jul 22, 2021 10:24 am

I guess upgrade to a T90, lots of people have done it and there are many threads. Some others do a T98 but those are hard to find. What’s wrong with you T84?
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Re: alternatives to the T84?

Post by Rod Rushton » Thu Jul 22, 2021 9:54 pm

Sure, the T84 has its limiations - but it is more than 75 years since it was designed, and I do not know what the original specifications called for. For sure there are thousands of them still giving good service. I can only assume badly assembled or poorly put together ones having seen already a long life could be the problem.
All the "modifications" I have done to my '44 GPW are not aimed at increasing the power output (insurance companies take a dim view of that in the UK) but reliability was alway my goal, and in the 10years and 7500 miles since I rebuilt it nut from bolt, the only time it let me down was of my own making by forgetting to put the plug back into the alternator. One modification I am very pleased with was the addition of one of Herms' overdrives - not to give me more speed, but to quieten engine noise! Also free-wheel front axle hubs, etc, etc,I recently decided to try out the French "strengthened" kit of brand new components - see my previous post- as towing my 1 ton caravan around France and Brittany did test the Jeep's limits - but it never let me down.
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Re: alternatives to the T84?

Post by mboardman » Fri Jul 23, 2021 8:10 am

I guess Im just gunshy of the T84. Had numerous problems with my first jeep, had to pull the tran 3 times while I owned her. Never was a great shifter - get stuck, rattled, wouldnt go into gears, and made me wary of parking on the slightest hills. On the bright side, I did have the motivation to make darn sure that parking brake was the best it could be!

The T90, kinda forgot about that. I guess I hoping there had been someone who had experimented with other trans since I did my last jeep in 2009.
42 GPW 78812*(dod 11/16/42)
Willys trailer # 33768
1951 dunbar kapple trailer # 01172524

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Re: alternatives to the T84?

Post by Rod Rushton » Fri Jul 23, 2021 9:13 am

My opinion - for what it's worth- would be to find a nice M38. My experience with the one I have is that they are everything the MB/ GPW should have been - better g/box and transmission, better steering, better brakes, more comfortable seating position proper screen wiper system,24v system usually means better starting, better lights, etc, etc,etc. - and to the uninitiated it still looks like the JEEP we love and know - despite being nearly 70 years old!
Best of all, although quite rare, the M38CDN was built and badged by FORD - what more could you want?
Love your Jeep - Faults and all
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Rod Rushton - Winner 2013 MVT Wilkinson Sword Trophy
Exeter Devon UK
FORD GPW 202055 DoD 5 - 22 - 44 Serial# 20534360
MBT # 25553 DoD 4 - 43
Piper Cub 1944 L4H 480015 G-AKIB

1942 CHEVROLET G506 CARGO. #2NM 213219
1943 AUSTIN LIGHT UTILITY M6448770

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Re: alternatives to the T84?

Post by Sargent Resorator » Thu Jul 29, 2021 12:58 pm

In my 44 GPW I went with a rebuilt T-90 and later Dana 18 transfer case. parts are easily available.
Image
Now I and driving around with no problems, and
with a way stronger trans and transfer combo.

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Re: alternatives to the T84?

Post by Donovan » Thu Jul 29, 2021 5:56 pm

I may regret this post the next time I drive my vehicle….I hope not!

My vehicle is close to 1000 lbs heavier than a standard WWII jeep and my T84 transmission works fine after 10,000 miles! Now I will say it is a finicky transmission to rebuild correctly but it can be done even by a novice like me with the help of knowledgeable people with the right machining equipment. In my instance, the rear washer on the main shaft had to be “shaved” to get the right clearance for the synchronization gears to work properly! Also, the machinist friend eyed what he thought was the proper clearance for the synchros to work. Everything works properly and the transmission shifts nicely! I have no problems with the T84! However, in my case, changing the transmission and transfer case would have major implications in making everything else work on the vehicle. Thus, I was motivated to keep everything original!
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Re: alternatives to the T84?

Post by Mike C » Fri Sep 24, 2021 2:39 am

Not from a Saturn car, but a different brand Saturn Overdrive. I believe the Saturn is the old Warn that replaces the bull gear on the Dana 18 in the PTO output creating overdrive. THe units work well and are quite popular in the CJ world. Herm the Overdrive guy is a source for rebuilt overdrives and I believe Advance Adapters makes the Saturn? Google will confirm for you with the limited info I supplied.

The T90 is a better trans than the T84 but requires modifications to the flat floor in the MB. I would want to keep the T84 unless my floor was already chopped. There is a T90c which has a lower first gear than the T90, it would also be on my short list as well as a 2.54 Dana 18 from an M38/A1 or CJ-5 if I was an off-roader.

If I wanted to drive an MB on the road a lot, I would probably change the ring and pinion to 5.38 and run the overdrive. If I was to want to improve off-road ability as well I would do the T90c and the lower geared Dana 18. That and a switch to 7.00 tires if not 7.50.
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