T84 transmission woes - _UPDATED_

[artificer]

This nut needs to be highly torqued as it causes the mainshaft & bearing with shims to become ONE integral component/piece.
Analysing your noise & that's what we are doing isn't it?....that nut is not the cause of the problem, we could hear.
A floating counter gear could allow interference if it is 0.040".

[wc56daveyboy]

I agree, John. Just asking since he posted that nut torque as a consideration.

I still feel that the huge amount of axial play in the cluster gear set (0.040-0.050", estimated) will end up being the culprit.

Ps. The bottom gear set with all the gears machined into one...Is it officially called a "counter gear" or a "cluster gear"?

[artificer]

Both names are correct. Depends where one was educated in the trade.

[Michael Browne]

you might want more clearance than that for oil flow

That is why counter gears have a oil hole central drilling & some countershafts have a long flat cutout in the centre as a reservoir to ensure good oil supply.
As well some bushings & thrusts are scrolled to distribute oil plus the mickey mouse cutouts in the rear spacer/thrust are meant to be filled with oil.
The lower end of the tolerance is always better than the largest & would not be given if inadequate.

0.004" is the minimum clearance specified for the T84 and is sufficient to allow an oil film on the thrust faces of the countershaft gear. The TM has 0.016" ( 0.4mm) as the service limit, this means that any clearance measurement between these values ( 0.004" - 0.016" ) is quite acceptable.

The lubrication of the countershaft gear bushings is achieved by the oil pockets cast into the inside of the main casing at the front and rear. The front pocket also serves as a position for the tab on the front thrust washer to locate and prevent spinning of the washer. The hardened rear thrust washer is located by a pin in the rear of the case and there is a brass or bronze washer between it and the countershaft gear, both of these washers have the cutouts (mouse ears) to allow oil to flow into the gear bushes.

The oil flows from the pockets through the cutouts ( mouse ears ) in the thrust washers and into the bushings and exits the gear via the drilled hole in the centre. The oil does not enter via the hole when running as the centrifugal force prevents it from happening.

When rebuilding the gearbox the countershaft gear clearance can be adjusted by changing the thickness of the bronze washer to achieve the desired clearance. I personally prefer to set toward the lower limit but any clearance up to 0.010" is acceptable on a fresh rebuild. The TM specified service limit of 0.016" is not what you would want in a rebuild as it doesn't allow for any further wear to occur before it is out of spec. However I have seen many T84 transmissions with far greater clearance and not showing any operating problems.

In this particular transmission (daveyboy) if it has a clearance of around 0.050" (1.2mm ) then one of the rear thrust washers may be missing or broken up and the countershaft gear will be driven rearward in the case by the axial thrust of the helical cut of the main drive gear. When the countershaft gear moves rearward more than designed the 1st gear cut will foul on the 1st / reverse slider gear and result in the horrible gear clashing noise in the original movie.

This leads me to to think of a couple of possibilities .......
1 - the washer was missing in the first place, not likely but possible
2 - countershaft gear clearance was not set correctly on rebuild, not likely but possible
3 - the new case was out of spec and point 2 above was not followed, not likely but possible
4- the thrust washer was faulty and broke up when in service and fell out of position and allowed the countershaft gear to move back too far and clashing with the slider gear, possible but why did it break up in such a short time, less than 30 or 40 miles,
a - maybe clearances set too tight when rebuilt, not likely but possible
b - no oil in the case from first startup..not likely but possible, can happen to anyone

The report from the rebuilder will shed some light on what has happened as there will be evidence of what went wrong.

[Chuck Lutz]

Unfortunately, the T84 overhaul requires some fitting to return it to original, factory specs...
1) Case: there are tolerances for the face-to-face internals that will effect the combination of new parts actually being within spec.
2) Cluster: NOS French or modern repop also have different lengths that may or may not effect the overall axial play.
3) Thrust Washers: Each of the three can be found as original and having a few thousandths difference in thickness which again and add or subtract to the overall axial play.

a) You MUST use a torque wrench or impact wrench on the castle nut and THEN check the play on the 3rd blocking rings. This requires you to assemble the T84 and measure, possibly disassemble and add/subtract a thicker SPACER behind the snap ring on the main shaft or use one of Ron's shims.
b) Insuring the poppet balls are in the proper position and only ONE spring is beneath them, not a half or broken old one.
c) Checking the shift rails for spec and rolling them on glass to see if they are out-of-round is suggested.

Finally, if a rebuilder just grabs a bunch of parts and does not pay attention to the above (and some other issues), then he needs to be lucky!

The broken piece of metal and steel particles tell us this rebuild was botched...finding where they came from will indicate why the T84 does not operate as it should I think....then again, there may be more than ONE problem and the different symptoms may be confusing the diagnosis properly.

Can't wait to hear DETAILED explanation from the builder as to the problems you experienced.

[wc56daveyboy]

Wanted to be sure all who assisted me here seen my UPDATED first post now that (I think and hope) that this issue is behind me.

If you didn't see where I updated my first post here it is now:

*** Guys.. update as promised.

I sent back the transmission to the rebuild shop, and after about a week or two, it arrived by Fedex here at home.

Last week I re-installed it, buttoned up the drive train and fired it up. drove around with my home made temporary seat for awhile, and lo and behold, it seems that all is now good.

Cause? well that is the hard part, as they didn't admit to anything on their end as being the cause, but rather a "defective" syncro hub being the reason for all this.. and as they kept saying, a "heavy" forced shift from me causing this. they even included one of the pawls from the syscro as evidence of the issue (I don't see a thing wrong with that pawl, BTW)

I didnt buy the defective syncro hub as being the culprit, of course, and stuck to my argument that I NEVER forced any heavy handed shifting in this jeep. Which I NEVER did either.

I also noted to my contact there at the shop the extremely loose fore and aft movement of the bottom cluster, and to BE SURE to look into this.

I did look at the tranny internally before re-installing it, and for sure they took more of the fore and aft slop out than it had previously. They even commented that it was a "Bit" excessive but nothing to cause what I seen... again, I was pretty adamant about that bottom slop, and I really think this was the issue all along..

anyway, its back up and running in the jeep with no issues experienced like prior.

I do wish to thank all who have commented here, and directed me where to look before removing and sending back. At least I had some higher level
of knowledge base on this transmission to talk Intelligently over the phone, rather than "its broke dude... please fix it"

In any case my utmost thanks and appreciation goes out to each and every one of you and your helpful posts.

[dinof]

Where was the shop that did your work? Just curiuos. Glad they stepped up and finally took care of it.

[wc56daveyboy]

So I'll go out on a limb here and reveal the builder.

I had this rebuilt by Herm the overdrive in Washington state.

I went with him only because I heard very good reviews on other off road and/jeep willys sites about his work, so I took the chance and went with them.

I'm revealing this now because he didn't seem to mind disclosing that he is the builder of these transmissions that are sold thru others like willys kaiser, Walcks as well as others I see selling them retail.

Now he (my contact their) also mentioned they were "getting out of rebuilding the T84" transmissions and likely was the last one he would be working on.

He stated there has been far too much work involved in machining and dealing with off shore parts that just don't fit. And return work that costs them.

Not sure how to take that information but that's what was said

Now I don't know if they will really get out of building them going forward, but that's what I was told. His site still shows the t84 as available so??

Where will the other resellers get there's from now? No idea.

I'll end this with the fact that he (my contact there) was most helpful thru all this, but I do know they weren't happy about returned goods and having to do it twice. Not my fault as being the customer I thought. Still good guys to do business with.

[dinof]

I once e-mailed him about his info on his site about only using non-synthetic gear oil in the trans. I asked him why. He replied "If you want to use synthetic oil, you are on your own on this one" HUH?? I just asked him what he thought, and he replied that. Nothing more.

That's my experience. Maybe he should stop rebuilding transmissions if he can't handle returns. It's part of doing business with customers. That I do know.

[wc56daveyboy]

Yea. His site specifically says Gl oil only. Or it voids his wauranty.

I want to run synthetic in my tranny at some point due to past experience with running cooler and shifting better. Should I need to that is

Do u run synthetic in yours, Dino?

I had used in the past a royal purple synthetic. It was wonderful stuff. Shifting was so much smoother with it in there.

I had a brand new rear pumpkin that was running so hot it would burn your hand touching the diff cover. Added that stuff and it was so cool
It was almost unbelievable.

[dinof]

Yes, I sure do. Same stuff. Royal Purple synthetic. I use the 75w-140w one and it works just fine. It also is safe for ALL metals. Many people here use it as well. Not cheap either. $18.00 a bottle.

All due respect, before he blames synthetic oil for anything, he needs to watch his people & secure better parts. I was turned off with this guy from the start.