T90a to T90c...need for clarification |
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omicron
Member Joined: 08 Aug. 2013 Location: Utica Indiana Status: Offline Points: 57 |
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Posted: 12 Oct. 2013 at 5:37pm |
Ok, I'm curious about this swap.. Is there anyone on here that has done this personally.. I'd like to pick your brains about the process, parts need, and other q's I've not been able to find out.
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oldtime
Member Joined: 12 Sep. 2009 Location: Missouri Status: Offline Points: 4131 |
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T90 A... verses ...T90 C The T90 A case is drilled to accept the oil collector part # 51 while the T90 C does not use the oil collector. http://www.film.queensu.ca/CJ3B/Photos/Par...ransmission.gif As you can see the overall gear span was greatly increased. In fact the Borg Warner T90 C provides the greatest gear span of any 3 speed. The following is an excert from: Everything You Ever Wanted to Know About CJ-3B Speed and Then Some For our model of jeep there were two differing transmission input ratios in use. See bulletin # 600: http://www.film.queensu.ca/CJ3B/Phot...B600Tranny.JPG Since slightly more hp was realized by the 134 engines progression,a slightly faster vehicle speed became feasable. So in model year 1963 the transmission low gear ratio was increased. This transmission change was done to offset the simultaneous axle change from the 5.38 ratio to the 4.27 ratio. With this combination of 3 changes including the ,engine, transmission and axle; the maximum vehicle speed would be increased without adversely raising the minimum (crawl) speed. In the transmission this change was manifest by changing the main drive tooth count from 18 teeth to 16 teeth plus also changing the driven cluster gear tooth count from 33 teeth to 35 teeth. Remember these particular driving and driven gears can only be interchanged as a set. Here then we have two different T-90 variants that were used in the 3B. Below are the gear ratios for both the pre 1963 (early) Borg Warner T-90 A and the post 1962 (late) T-90 C. ...................T-90 A .......T-90 C (INPUT)......(INPUT).....(OUTPUT) 1st gear......2.798.....3.339 1.00 2nd gear.....1.551.....1.851 1.00 3rd gear......1.000.....1.000 1.00 reverse.......3.798......4.531 1.00 As you can see from the numbers the velocity of the transmission output drive will be affected by gear selection. The transmission velocity is to be understood as a numerical ratio, input to output. Low gear ratios reduce a vehicles resistance to the force by decreasing traveled distance. The minimum output for the early T-90 A in 1st gear is ( 600 divided by 2.798 =) 214 rpm. The minimum output for the latter T-90 C in 1st gear is ( 600 divided by 3.339 =) 180 rpm. High gear is always a straight through drive without gear reduction. So the maximum output for both T-90's in 3rd gear is 4000 rpm. As you can now see the T-90 C has a greater gear ratio spread. |
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Currently building my final F-134 powered 3B .
T98-A Rock Crawler using exclusive factory parts and Approved Special Equipment from the Willys Motors era (1953-1963) Zero aftermarket parts |
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Mike S
Member Joined: 20 May 2006 Location: West Coast Status: Offline Points: 2318 |
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I just had my T90A reworked to a T90C. This required a new input shaft/gear and a new cluster gear set. The oil collector was deleted. No modifications to the case, clutch, or other components were required.
I have not installed it yet - just finished painting it.
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'47 CJ2A -- #114542
Warn FF D41 rear Lock-Right locker 11" drum brakes Dual master cylinder T90C Transmission 16 X 6 Jeep truck wheels Cooper STT Pro tires |
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omicron
Member Joined: 08 Aug. 2013 Location: Utica Indiana Status: Offline Points: 57 |
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Ok, can I swap the t90a out for a t90c, or can I only swap the internals around?
I'm running 33" tires and I'm a bit fast on trail, I'm wanting to slow it down a bit to make those rocky trials not so bruising. |
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omicron
Member Joined: 08 Aug. 2013 Location: Utica Indiana Status: Offline Points: 57 |
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Mike S, where did you get your parts from?
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Mike S
Member Joined: 20 May 2006 Location: West Coast Status: Offline Points: 2318 |
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The T90A and T90C are the same and interchangeable as far as fitment to the engine/bellhousing.
I got my parts from Herm the Overdrive Guy. Around $200 for the components - new.
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'47 CJ2A -- #114542
Warn FF D41 rear Lock-Right locker 11" drum brakes Dual master cylinder T90C Transmission 16 X 6 Jeep truck wheels Cooper STT Pro tires |
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omicron
Member Joined: 08 Aug. 2013 Location: Utica Indiana Status: Offline Points: 57 |
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Understood... Seeing how my trans is in pretty good shape, I think I might just swap in new internals
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oldtime
Member Joined: 12 Sep. 2009 Location: Missouri Status: Offline Points: 4131 |
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If using the T90 A case with T90 C parts you will need to eliminate the oil collector. The T90 A and T90 C have slightly different cases.
The T90 A case can be used for T90 C applications but technically speaking it is modified.
To modify, you simply need to plug the 2 oil collector holes of the T90 A case.
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Currently building my final F-134 powered 3B .
T98-A Rock Crawler using exclusive factory parts and Approved Special Equipment from the Willys Motors era (1953-1963) Zero aftermarket parts |
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Jesse 1946
Member Joined: 17 July 2012 Location: Niwot, Colorado Status: Offline Points: 144 |
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Hey Oldtime, decided to Tare in and rebuild my T90, first time so bare with me. It seems that the P.O used a T90 A- 1 case and T90 C gears inside as you guys were talking about. Where I'am confused is my case does not have the oil collector as you mention the T90 A should. Am I missing something. My thought from reading other threads that possibly this tranny is out of a CJ5. Tag numbers are 946109/AS5-T90L also due you have any idea what these numbers stamped on top of case are. 27 92. Just below the shifter top. Thanks
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Jesse
1949 CJ 3A 1942 GPW #29857 |
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gunner
Member Joined: 05 Dec. 2005 Location: NW Status: Offline Points: 157 |
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Has anybody done the conversion to T90C and kept their 5.38s? How does it drive going up through the gears? |
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Mike S
Member Joined: 20 May 2006 Location: West Coast Status: Offline Points: 2318 |
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I have the T90C gears with 5.38 gears. I'll let you know how it works when I finish the Jeep. If not low enough, maybe a TerraLow TC is in my future. For comparison the 'crawl ratio' with the T90C is 44.2 - not much when compared with the numbers you could get with SM420 (7:1) or a T18... the crawl ratios for these with 5.38s is in the 90s.
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'47 CJ2A -- #114542
Warn FF D41 rear Lock-Right locker 11" drum brakes Dual master cylinder T90C Transmission 16 X 6 Jeep truck wheels Cooper STT Pro tires |
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gunner
Member Joined: 05 Dec. 2005 Location: NW Status: Offline Points: 157 |
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Nothing compares to the truck trannys but the T90 will stay in my jeep. I was wondering not so much the crawl ratio as how it would drive on the street just going up through the gears. The engineers calculate these things out for a reason and I'm concerned that putting the T90C conversion in with 5.38s might result in reduced driveability on the street.
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Mike S
Member Joined: 20 May 2006 Location: West Coast Status: Offline Points: 2318 |
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The T90C was installed in later Jeeps with 4.88 differential gearing.
T90C first gear is 3.34. This is a bit lower than the T90A. Second is also a bit lower, Third is 1:1, so that is unchanged. I expect that you will find it very driveable. If it is a concern, go with standard T90A gearing.
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'47 CJ2A -- #114542
Warn FF D41 rear Lock-Right locker 11" drum brakes Dual master cylinder T90C Transmission 16 X 6 Jeep truck wheels Cooper STT Pro tires |
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oldtime
Member Joined: 12 Sep. 2009 Location: Missouri Status: Offline Points: 4131 |
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The T90C was installed in later Jeeps with 4.88 differential gearing.
That's not correct.
All CJ's 1945-1963 were standard with T90 A and 5.38 FDR.
All post 11/62 Hurricane CJ's were standard with T90 C and 4.27 FDR.
Actually the T90 C gearing was originally developed for use with the 1940's Willys pickups.
The early pickups were all equipped with 4.88 FDR. Am I missing something.
The case used for T90 C is nearly identical to the T90 A case.
It's the exact same case but the oil collector holes are not drilled through the casting.
Tag numbers are 946109/AS5-T90L
That indicates post 1964 vintage.
Has anybody done the conversion to T90C and kept their 5.38s? How does it drive going up through the gears?
It effect the TAKE OFF RATIO
Standard take off ratio is 15/1
Using T90 C produces 18/1 take off ratio
You'll likely roll through stops in second gear without down shifting
1st will be slightly lower and that's great when in traffic jams |
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Currently building my final F-134 powered 3B .
T98-A Rock Crawler using exclusive factory parts and Approved Special Equipment from the Willys Motors era (1953-1963) Zero aftermarket parts |
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gunner
Member Joined: 05 Dec. 2005 Location: NW Status: Offline Points: 157 |
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Thanks for the clarification. I hadn't thought about rolling through stops and just keeping it in 2nd gear. Reason I'm asking all this is I'll be tearing into the T90 before long and doing a clutch job as well. Now's as good a time as any to make the conversion to a T90 gearing if I'm going to do it at all. I want to put in NOS parts. I have quite a few already but would still need to get the cluster and input shaft. One can still get NOS input shafts for the T90C, but I haven't seen any T90A inputs in a long time. Traffic jams? I live where I live partially because there are none. On the street the lower gearing would help while the jeep is in the 4th of July parade, though. |
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Mike S
Member Joined: 20 May 2006 Location: West Coast Status: Offline Points: 2318 |
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Following from Novak's 'knowledge base' --
T90C The T90 used from 1963 to 1971 with the F-head four-cylinder engine is designated as the T90C. It features top shifters, a 7" input shaft (stick-out length) with 15/16" x 10 splines and a felt-sealed front bearing retainer assembly. Since the T90C uses a case marked "T90A", you will need assurance that the transmission in question came from a post-'62 Jeep, or you will need to pull the top cover and count teeth. The T90C has a 16 tooth, helically cut input gear. The cluster gear has a 35 tooth driven gear, resulting in a 3.34:1 first gear and a 1.85:1 second gear. Gear ratios T90A: first 2.79, second 1.55, third 1.0 T90C: first 3.34, second 1.85, third 1.0 They also have a nice gear calculator here: http://www.novak-adapt.com/knowledge/gearing.htm
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'47 CJ2A -- #114542
Warn FF D41 rear Lock-Right locker 11" drum brakes Dual master cylinder T90C Transmission 16 X 6 Jeep truck wheels Cooper STT Pro tires |
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gunner
Member Joined: 05 Dec. 2005 Location: NW Status: Offline Points: 157 |
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Well, I understand all about the ratios and such. What I'm trying to get at is this: right now, with a T90A set up in my jeep, it drives just fine in 2 wheel drive. It goes up through the gears in as fluid a motion as these vehicles can go and makes it enjoyable to drive. Overall, I'd say the engineers got it right on their gearing and spacing. I have no complaints over it. Notice I say going up through the gears; I realize that both set ups have 1:1 in 3rd gear and so cruising speed is the same. I just don't want to either lug the engine or over rev it due to the mix of parts. The reason for going to the T90 C is to get better gearing in 4x4 especially compound low. A crawl ratio of 44:1 may not seem very good compared to something in the 70-90:1 range achievable with a truck 4 speed, but it's still very good considering I won't be rock crawling. It is definitely and noticeably better than the 36:1 in T90A configuration. But it doesn't sound like there is anybody out there who has done this conversion and kept both the 5.38s and the F-head (Mike, let us know when you have test driven your conversion with the T90C). Guess I'll have to stay with what I have or take a chance. I'm inclined to go for the conversion especially as I may put in an overdrive in the future. Edited by gunner - 26 Jan. 2014 at 6:44am |
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Mike S
Member Joined: 20 May 2006 Location: West Coast Status: Offline Points: 2318 |
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Gunner - I really don't expect to see a lot of difference except it will be a bit slower on take off from a standing start. Since I don't use my Jeep much on hardtop, I elected to go with the T90C set up for the same reasons you stated. The 134 has a fair amount of low end torque and the 2A is a lightweight vehicle.
It will probably be summer before I finish my WIllys to be drivable.
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'47 CJ2A -- #114542
Warn FF D41 rear Lock-Right locker 11" drum brakes Dual master cylinder T90C Transmission 16 X 6 Jeep truck wheels Cooper STT Pro tires |
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