Forum Home Forum Home > CJ-2A Discussion Area > Modifications from original
  New Posts New Posts RSS Feed - T90a to T90c...need for clarification
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

T90a to T90c...need for clarification

 Post Reply Post Reply Page  12>
Author
Message
omicron View Drop Down
Member
Member


Joined: 08 Aug. 2013
Location: Utica Indiana
Status: Offline
Points: 57
Post Options Post Options   Thanks (0) Thanks(0)   Quote omicron Quote  Post ReplyReply Direct Link To This Post Topic: T90a to T90c...need for clarification
    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.

Thanks!
Back to Top
oldtime View Drop Down
Member
Member
Avatar

Joined: 12 Sep. 2009
Location: Missouri
Status: Offline
Points: 4131
Post Options Post Options   Thanks (0) Thanks(0)   Quote oldtime Quote  Post ReplyReply Direct Link To This Post Posted: 12 Oct. 2013 at 5:55pm
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.

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

Back to Top
Mike S View Drop Down
Member
Member


Joined: 20 May 2006
Location: West Coast
Status: Offline
Points: 2318
Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike S Quote  Post ReplyReply Direct Link To This Post Posted: 12 Oct. 2013 at 6:25pm
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. 
'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
Back to Top
omicron View Drop Down
Member
Member


Joined: 08 Aug. 2013
Location: Utica Indiana
Status: Offline
Points: 57
Post Options Post Options   Thanks (0) Thanks(0)   Quote omicron Quote  Post ReplyReply Direct Link To This Post Posted: 13 Oct. 2013 at 2:46am
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.
Back to Top
omicron View Drop Down
Member
Member


Joined: 08 Aug. 2013
Location: Utica Indiana
Status: Offline
Points: 57
Post Options Post Options   Thanks (0) Thanks(0)   Quote omicron Quote  Post ReplyReply Direct Link To This Post Posted: 13 Oct. 2013 at 2:47am
Mike S, where did you get your parts from?
Back to Top
Mike S View Drop Down
Member
Member


Joined: 20 May 2006
Location: West Coast
Status: Offline
Points: 2318
Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike S Quote  Post ReplyReply Direct Link To This Post Posted: 13 Oct. 2013 at 4:40am
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.
'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
Back to Top
omicron View Drop Down
Member
Member


Joined: 08 Aug. 2013
Location: Utica Indiana
Status: Offline
Points: 57
Post Options Post Options   Thanks (0) Thanks(0)   Quote omicron Quote  Post ReplyReply Direct Link To This Post Posted: 13 Oct. 2013 at 5:46pm
Understood... Seeing how my trans is in pretty good shape, I think I might just swap in new internals
Back to Top
oldtime View Drop Down
Member
Member
Avatar

Joined: 12 Sep. 2009
Location: Missouri
Status: Offline
Points: 4131
Post Options Post Options   Thanks (0) Thanks(0)   Quote oldtime Quote  Post ReplyReply Direct Link To This Post Posted: 14 Oct. 2013 at 3:52pm
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.
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

Back to Top
Jesse 1946 View Drop Down
Member
Member


Joined: 17 July 2012
Location: Niwot, Colorado
Status: Offline
Points: 144
Post Options Post Options   Thanks (0) Thanks(0)   Quote Jesse 1946 Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan. 2014 at 4:42am
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
Jesse
1949 CJ 3A
1942 GPW #29857
Back to Top
gunner View Drop Down
Member
Member


Joined: 05 Dec. 2005
Location: NW
Status: Offline
Points: 157
Post Options Post Options   Thanks (0) Thanks(0)   Quote gunner Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan. 2014 at 5:03am

Has anybody done the conversion to T90C and kept their 5.38s? How does it drive going up through the gears?

Back to Top
Mike S View Drop Down
Member
Member


Joined: 20 May 2006
Location: West Coast
Status: Offline
Points: 2318
Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike S Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan. 2014 at 5:51am
Originally posted by gunner gunner wrote:

Has anybody done the conversion to T90C and kept their 5.38s? How does it drive going up through the gears?


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.
'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
Back to Top
gunner View Drop Down
Member
Member


Joined: 05 Dec. 2005
Location: NW
Status: Offline
Points: 157
Post Options Post Options   Thanks (0) Thanks(0)   Quote gunner Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan. 2014 at 6:26pm
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.
Back to Top
Mike S View Drop Down
Member
Member


Joined: 20 May 2006
Location: West Coast
Status: Offline
Points: 2318
Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike S Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan. 2014 at 8:06pm
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.
'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
Back to Top
oldtime View Drop Down
Member
Member
Avatar

Joined: 12 Sep. 2009
Location: Missouri
Status: Offline
Points: 4131
Post Options Post Options   Thanks (0) Thanks(0)   Quote oldtime Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan. 2014 at 10:37pm
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
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

Back to Top
gunner View Drop Down
Member
Member


Joined: 05 Dec. 2005
Location: NW
Status: Offline
Points: 157
Post Options Post Options   Thanks (0) Thanks(0)   Quote gunner Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan. 2014 at 11:18pm

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.

Back to Top
Mike S View Drop Down
Member
Member


Joined: 20 May 2006
Location: West Coast
Status: Offline
Points: 2318
Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike S Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jan. 2014 at 5:43am
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
'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
Back to Top
gunner View Drop Down
Member
Member


Joined: 05 Dec. 2005
Location: NW
Status: Offline
Points: 157
Post Options Post Options   Thanks (0) Thanks(0)   Quote gunner Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jan. 2014 at 6:38am

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
Back to Top
Mike S View Drop Down
Member
Member


Joined: 20 May 2006
Location: West Coast
Status: Offline
Points: 2318
Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike S Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jan. 2014 at 6:22pm
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. 
'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
Back to Top
 Post Reply Post Reply Page  12>

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.06
Copyright ©2001-2022 Web Wiz Ltd.