T90 Question |
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Mike S
Member Joined: 20 May 2006 Location: West Coast Status: Offline Points: 2318 |
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Posted: 01 Aug. 2007 at 1:27pm |
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I had the T-90 rebuilt several years ago, but it still slips out of second gear under load. I understand that this is a common problem with these trannies, and that there is sosme sort of bushing change or shim that needs to be done. Anybody point me to a source of info on this?
Thanks Mike |
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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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samcj2a
Member Sponsor Member x 5 Joined: 21 Oct. 2006 Location: Arlington, VA Status: Offline Points: 8549 |
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In my experience, the fix is to replace both the synchronizer ring and second gear. If both were not replaced in the rebuild, I'd do that.
When those two parts are new, the surfaces where they engage look as though they are worn - as though the corners of the teeth are rounded off. Someone that is not aware of the T90's tendency to develop this problem might not notice that the teeth are worn too much because, at first glance, they look similar to how they appear when new.
If there's a shim somewhere, I'm unaware of that as a fix.
Edit: I just noticed your comment and "under load". The classic case is when it is under load as you are slowing down in second gear. If it is slipping out when you are accelerating under load, that is more unusual, I think. Edited by samcj2a - 01 Aug. 2007 at 1:38pm |
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Militoy
Member Joined: 15 May 2007 Location: California High Desert Status: Offline Points: 231 |
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The "decell - pop out of second" problem is the "classic" first sign that a T90 needs an overhaul. A few years ago my son converted the CJ6A to front disc brakes. He made a minor error in the way the new brake dual cylinder bleed valving was handled - and we almost wound up at the bottom of a deep aqueduct as a result. Without going into the whole story - we popped out of gear downhill on a bumpy, vertical trail above the DEEP concrete channel, just at the time when the brakes went to "zero" effectivity. Couldn't get it back into gear with all the bouncing, so I pointed it straight through some big bushes to slow the descent. Sam has described the fix pretty well. Mike all the parts, and check clearances to factory specs when you break it down - and replace any parts that aren't close to spec. Do you have a factory manual?
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48 CJ2A; 49 CJ3A; 53 M38A1; 66 CJ6A Tux Park; 70 M561(Gama Goat); 75 Cherokee [2X (series)transmissions, 12K underchassis Braden winch]; M151 engines/trans FS
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Mike S
Member Joined: 20 May 2006 Location: West Coast Status: Offline Points: 2318 |
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Thanks. Yes, it pops out of gear under compression braking when going down hill. I have had no adventure such as Militoy has... but it is still a PITA.
I have the manual. SO a new second gear and synchro will fix this, and I can get on to the next problem? Sigh. |
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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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jpet
Moderator Group Sponsor Member x 5 Joined: 30 Apr. 2008 Location: Ramsey, IL Status: Offline Points: 11173 |
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The synchro is just the brass multi-toothed part correct?
Does anyone know of a vendor who has a kit to perform this fix, i.e. gaskets, seals, 2nd gear, second gear synchro?
I'd like to fix mine but I would like to have the parts ready before teardown to keep my jeep's offline status to a minimum.
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sean
Moderator Group Sponsor Member Joined: 20 July 2005 Location: North Idaho Status: Offline Points: 7388 |
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Jeff:
The sliding collar is rarely worn out, since it's hardened steel, but it does have teeth, just like 2nd. gear, and should be checked for excess wear. The syncro hub is an unlikely suspect, but if it's worn to the point that it wobbles on the mainshaft, it should be replaced too. Mike:
2nd. gear is helical cut. So under load, forces pull the gear forward, into tighter mesh w/the syncro collar. When you let off the gas pedal, forces change direction (from drivetrain to engine), and try to pull the gear backward, away from the syncro collar. Now, if 2nd. gear bushing is worn out, allowing the gear to wobble on the shaft, it will try to tip out of the syncro collar. Worn bushing, combined w/worn syncro teeth, cause the pop out of gear. The potential additional problem comes from the way 2nd. gear & mainshaft fit together: there's no thrust washer used, so if 2nd. gear wobbles badly, it can wear away the thrust face on the mainshaft, to the point where even new gear & syncro won't fix it (2nd. gear can still move backward far enough under deceleration to cause it to pop out). How bad it is just depends on how many miles have been put on it in this condition. The "shim" band-aid method is meant to compensate for a worn mainshaft, by moving it further forward than original, closing the excess gap left by the worn out gear thrust face. So in worst-case, you might need to replace the mainshaft (or use the shim band-aid). It's not often needed, but be aware of the potential. Check all the fit tolerances before & after reassembly to be sure. Sean Edited by sean - 07 Sep. 2008 at 3:54pm |
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Keith.Tracy
Member Joined: 27 Sep. 2006 Location: Hydes, MD Status: Offline Points: 573 |
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Novak has a great rebuild kit that has the "fixes" for these problems.
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jpet
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That's what lowenuf said. I'll check'em out.
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TERRY
Member Sponsor Member Joined: 22 May 2007 Location: BOULDER COLORADO Status: Offline Points: 3400 |
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I thought Sean had recently posted a factory service bulletin on this subject that placed a lot of emphasis on the 2-3 shift fork wearing, or poppet springs being weak. Mine was freshly rebuilt with new 2nd gear, new synchro and rings and an nos mainshaft and it went ahead and popped out of 2nd!! I have not gone back to re-check the shift fork yet.
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BOULDER 48 2A
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Pat T.
Member Joined: 14 Feb. 2006 Location: Central IL Status: Offline Points: 675 |
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Terry
That was the same thing mine was doing and it ended up being the shift forks were lose on the shaft. I cleaned up the shift tower and put new roll pins on the shift forks and made grooves on the slide rods so that oil could get back into the transmission instead of being forced out at the ends of the slide shaft when shifting and it doesn't come out of second gear now. Pat |
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Wild Bill
Member Joined: 08 July 2008 Location: Spring City, Pa Status: Offline Points: 36 |
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Walcks 4WD has a real good kit as well. I've used their kit, and I havn't had any gears popping out of gear.
http://www.walcks4wd.com/Default.aspx |
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1946 Willys CJ2A w/3 on the tree
1964 Willys CJ5 w/351 Windsor Jeep is not a luxury ride, stop building soccer mobiles!! |
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sean
Moderator Group Sponsor Member Joined: 20 July 2005 Location: North Idaho Status: Offline Points: 7388 |
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Here's a good example of completely worn out sliding collar.
The 3rd. gear side is slightly worn & burred, but still has fairly well defined spline tips that extend to the edge of the collar: 2nd. gear side is clearly worn out. Should look more like the teeth above: If you replace this part, inspect the new one carefully. There are defective, made in USA, parts out there. This one was improperly milled, wasting half the spline tips. It would not have shifted very well: Sean |
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