T90 Problems - Diagnosis??

While taking my Jeep out on the back roads last night for the final check to get ready for a jeep outing coming up soon, I had a transmission "glitch".

For the last couple of years, every once in a while, the tranny would "pop" out of 2nd gear on a down hill or when no power was applied. Usually only in low range, since that's where I spend most of the time in.

Last night, I was testing on a long uphill seasonal road and spent most of the time in 2nd - low range. When I got up the hill, I put it back in high range and proceeded home.

On the way home, I could barely shift it out of 2nd - high range. It would go in nice and easy, but it would only come out when it wanted to (once every 6 tries).

All other gears work fine, BUT backing up into my shop, the reverse was acting like it was "binding". I was in low range, with the hubs unlocked.

Again, all other gears work fine, except 2nd and reverse. Any ideas???

 

No locker, front or rear.
But that's what it feels like, turning with a locked front / rear. But I was driving straight in reverse and it was binding.

Is the 2nd and reverse the same gear?? I almost feels like the gear skipped a tooth and is binding. I don't know if that's possible or not.

 

i'd pull the transmission cover and look inside to see what's going on. I had this same problem...my t90 was popping out of 2nd, then one day is just got stuck in 2nd and I couldn't get it out of gear, no matter how hard I tried. After pulling the cover I found that one of those little spring tabs was broken and was wedging the t90 in 2nd. I don't know what the tabs are called, but they are the little tabs (spring loaded from the back with a big ring) in the sliding hub that engages the gears. The back of one of those tabs had broken off. I could easily shift into 2nd, but once it was there that broken tab would stick up at an angle and wedge that hub in place.

 

Jeep has a name for them, but I think you are referring to the synchro clutch hub dogs. These are spring loaded, and a broken spring could cause the clutch hub to jam. These tabs are detents that hold the clutch hub against the 2nd gear, locking them together to give 2nd gear.

Popping out of 2nd is usually caused by aworn bushing inside 2nd gear. This makes the gear slightly skew on the shaft and pushes the clutch hub away from 2nd gear.

I'd not be surprised if the two problems are not related.

 

Does 2nd and reverse share the same gear?

 

any unusual noises coming from the trans while Jeep is idling with trans in neutral ?
you might try shifting the trans thru the gears with the t/case in neutral, takes the load/torque off of them but lets everything spin
I agree, I think it's 2 different problems
low and reverse share the same sliding gear; reverse idler is all by its lonesome.
it could be an endplay issue with the trans mainshaft; front/rear bearing going bad, hence the question about noise. That would jam the synchro hub as well.
Nut on bull gear tight ?

 

1st and reverse is the same gear...I think!

 

Last night I decided to investigate the issue. Before I started taking thing apart, I drove it around again. Everything seemed ok now... no binding and 2nd gear didn't "stick" anymore.

I drained the fluid... pretty nasty. I forgot that the last time out I pretty much submerged the jeep in water and I didn't change the fluids. Other than a brown color gear oil, nothing else came out. I noticed that there is some metallic "dust" on the bottom of the case, but I think that is just from wear and tear. No metal chunks or teeth on the bottom of the case.

I pulled the top shifter cover off and, from what I could see, everything was still there. The spring clips that was mentioned earlier where there, but they didn't cover the entire slot between the teeth. I don't know if that's the way its supposed to be like that, but there is about a 1/4" "Play" on each clip front to back. And the gear was fairly easy to slide back and forth... I would think that there would be more resistance with the spring clips to minimize the gear from sliding out..... Is this the cause for 2nd gear to pop out while engine braking??? Seems like it.

I also noticed that when in gear and I rock the jeep back and forth, the first gear on the main top gear assembly actually moves front to back about 3/16" (I think that is rotating on the lower shaft). This causes the the metal disk on the front inside of the case to retract from the case. I assume that this disk is to keep oil from coming out, and I did notice that I was leaking fluid out of the flywheel cover (outside of the tranny).

Again, I took a magnet and fished around the case and didn't find anything.

 

Here are some pics

 

Yup, those are the "spring clips" I was refering to. They seem to look pretty normal...but that's just from my limited experience, only pulling 3 or 4 t90s apart. That play you are seeing doesn't seem normal. Have you checked the big nut in the transfer case that holds the gear onto the output shaft of the t90? If that's loose you could see some play. Also, check the input shaft for play...you may have a bad bearing there, or the bearings in the main shaft could be sloppy, which would give some play and also kick it out of 2nd. As for a little metallic dust in the oil, that may have come from your oil collector getting chewed up a little when that gears moves out the way you explained.

 

I have a Warn Overdrive on the *** end of the x-fer case. Is there still the big nut on the end that holds the gear on to the output shaft?? Or was that replaced by the OD??? I'm trying to picture this in my head.

I am going to look at the Warn Overdrive manual online to see if there is anything on this.

 

FWIW, my T14 did something similar before it failed. Basically, some of the ball bearings started to fall out of the rear bearing into the transfer case, allowing the main shaft to move under load. It may have been causing my 2nd gear issue until too many fell out, which caused the binding issue. You may have a similar issue, or just a highly worn bearing. You may want to take the bottom cover off your Xfer case to make sure nothing has fallen out into it.

 

Thank's twiggs, I will drop the x-fer case cover tonight and inspect.

I think that I will also remove the OD and inspect as long as I am under there.

Thank's all... I will update.

 

Update:

Last night I removed the x-fer case cover and, thankfully, no suprises. Everything in there looked fine and tight.

I replaced the covers, dumped some gear oil in and took it for a test drive. It worked fine for about 1 mile . Second gear still sticks... bigtime.

Took it back to the shop and replaced the entire shift tower with one of my "spares" and tested again.

This seemed to work ok now. I drove for about 15 minuites, spent time in all the gears, high, low. OD, forward and reverse. Everything was tight and shifted properly.

But.......

When in neutral, with the clutch disengaged, I can hear gear noise. When I put a little pressure on the shifter (towards third gear) with the clutch disengaged, the gear starts grinding a little.

I think that the forks are a little too far forward (if I think correctly) and need to be adjusted back.

Is there any way that the forks can be adjusted?? Or just grab my sledge and handy flame thrower and have at it?? (Gently of course)

 

I wonder if you didn't get your shifter aligned properly before you put it on and one of the forks is hitting a gear.

 

Thought about that, but I can shift through all the gears fine. As far as I can see, there is only the forks on the shifter, and the gear "ring" that the forks slide into.

I feels like the gear that the fork is attached to is really close to the cluster on the bottom. I think that the gear that is close to is 3rd gear, which is the syncro cluster.

In the tranny, it's the helical gear all the way to the front (engine side)... I think that's 3rd gear???