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Re: Transmission new and something ain’t right...

Posted: Thu Oct 31, 2019 5:29 pm
by dinof
My transmission rebuild was a little different because it had nothing to do with any gear, spacer, shaft or anything that goes into the box. The box itself was a French copy (that someone reputable) was selling as "from France". Luc Cousens had a transmission case like mine and sure helped me see the light. My case was allowing the 2nd/3rd shift rail to travel more than normal and the synchro blocks were exposed to where it stopped you from Crimp One Off the jeep out of 3rd. To prevent this, I used a .040 snap ring to stop excessive travel and all was good to this day. Luc did the same thing with a spacer,
which was better than my snap ring. At least I knew that someone else identified the bogus cases that I thought were W.O.F.

It never was a problem years ago, but I suggest all here giving advice to include checking the travel of the shift rail to prevent this problem.
I went through the whole trans before knowing the real problem. And all I really had to do was put a snap ring (or spacer) and I would of saved a
great deal of time, money. Lesson learned the hard way.

Re: Transmission new and something ain’t right...

Posted: Fri Nov 01, 2019 7:14 am
by JeepdaddyRC
Thank you Wolfman, Chuck and Dinof.
I opened the T-84, replaced bearings, blocking rings, synchro hub and 2nd speed gear (with correct bushing) - all parts from RFJP .
Unfortunately, after reinstalling it came out of 2nd gear on a decline while letting off the throttle.
When letting off the throttle, you can see the gear shift lever move to the rear. When accelerating, it moves forward.
Now trying to figure out why it came out of second, and better understand the role of shims.
Really appreciate your help.

Re: Transmission new and something ain’t right...

Posted: Fri Nov 01, 2019 12:03 pm
by Chuck Lutz
Start in neutral:
1) remove the tower and shift cane and shift plate.
2) using a screwdriver, tap the 2nd/3rd shift fork into 3rd
3) using a small screwdriver, gently pry the 2nd gear blocking ring off the 2nd gear cone
4) rotate the blocking ring to insure it is not held too tight
5) using the small screwdriver, note how much slop (axial play) the 2nd gear blocking ring has

OK, let's move on.
1) align the 2nd gear teeth and the blocking ring teeth to make moving the hub easier
2) using a screwdriver, tap the 2nd/3rd shift fork into 2nd
3) using a small screwdriver, gently pry the blocking ring off the 3rd gear cone
4) using that small screwdriver, move in clock/counterclockwise to insure it is loose
5) note EXACTLY how much slop you see on the blocking ring/hub/3rd gear.
6) does the amount of slop on 2nd gear blocking ring and 3rd gear blocking ring seem equal? It needs to!

OK:
1) you should NEVER see so much of those three shift plates/dogs that the hump in the middle is exposed or sooner or later one will stand up and jam the gear box
2) the ideal amount of slop on 3rd gear blocking ring is the EXACT amount of slop on the 2nd gear blocking ring.
3) to arrive at the 3rd gear blocking ring measurement, you either add to the SPACER width one way or another or use one of Ron's shim kit shims or another spacer/
4) if you have the slop equal (axial play) then the synchro is in the middle of BOTH gears and the shift forks can move the SLEEVE on the synchro just the right amount for each gear and not let the three little shift plates escape.
5) this is what has been referred to as "fitting" and is a part of a good rebuild....

However:
Again, using a dummy T/C or the real one (with a reamed out take-out rear bearing to facilitate removal/installation a couple times while you get this all above accomplished), you are setting what will become the final depth of the main shaft into 3rd gear which is critical.

As to your shift cane moving back and forth....if you have too much slop on the Cluster Gear, it will move back and forth because 2nd gear on it is helical cut and that pushes/pulls on the main shaft helical cut 2nd gear and if the slop on the main shaft is too much it can pull 2nd gear out enough to pop out of gear.

It is critical to get both the cluster gear slop and the main shaft location (forward or rearward depending on 3rd gear slop) within spec.

Good Luck...

Re: Transmission new and something ain’t right...

Posted: Fri Nov 01, 2019 5:28 pm
by dinof
Good organization Chuck & included the all important check of shift plate exposure. Here is a good video on Chucks post
https://www.youtube.com/watch?v=Wd-b4oFCAfA&t=73s

Now here goes a question: My new rear bearing was not a tight fit. I was able to tap it on rather easily. In fact, I think it slid onto the shaft. Is that a problem? Transmission still working fine at this point.

Re: Transmission new and something ain’t right...

Posted: Fri Nov 01, 2019 6:45 pm
by Chuck Lutz
Dino...

I would first ask what mfger and part number you used to begin with as these are the KOYO Japanese bearings:
FRONT: 6207-NR-2RS I.D. = 1.3780"
REAR: 6307-2RS (or 2RD) I.D. = 1.3780"

The next question would be: Are you using an original main shaft or a repop? A good bearing on a bad main shaft might cause that one to slip on/off.

Again, I recommend re-using that front bearing snap ring along with the other suggestions I have posted thus far.

Re: Transmission new and something ain’t right...

Posted: Sat Nov 02, 2019 7:53 am
by Wolfman
Jeepdaddy.
In second gear, when you accelerate and decelerate ( on & off the throttle), the gear shift lever moves fore & aft.
1st thought. You do have the nut on the rear of the mainshaft, torqued really tight. Like around 100 Ft.Lbs.
For the gear shift lever to move back & forth, the shift collar on the synchronizer must be moving, taking the shift fork, shift rail & gear shift lever with it.
That would be a lot of collar movement.
Can't imagine there is that much movement of the synchronizer hub on the mainshaft.
I am thinking more likely the entire mainshaft assembly is moving. Either the rear mainshaft nut is not tight and the shaft is moving back and forth in the rear main bearing or the bearing has too much end play in the transmission/ T-case and the bearing is moving back and forth. Maybe a combination of both ??
I would start by removing the transmission top cover and pry on the mainshaft and associated parts. Determine where the excessive end play is.
May take a little pressure. You are trying to mimic the end force applied by the tapered gears, ( second gear and the rear mainshaft gear ), that are pushing and pulling on the mainshaft as they accelerate and decelerate a jeep.

Re: Transmission new and something ain’t right...

Posted: Sat Nov 02, 2019 10:46 am
by Joe Gopan
Another detail that wil cause everything on the Mainshaft to bind together are the three synchronizer shifting plates . These have seemed to be a problem for the past 20 years as the 3 plates that are being offered on the aftermarket can be too long and force the blocking rings into the second Speed Gear and the Main Drive Gear. I have missplaced my notes that have the factory specs for those 637832 Plates.

Hopefully, someone that has access to the Willys drawings can help us with that information.

Re: Transmission new and something ain’t right...

Posted: Sat Nov 02, 2019 11:50 am
by donk_316
This thread has made me second guess just about everything with my transmission rebuild.
When I get back home, I’m gonna pull the trans and xfercase, put them on the bench and triple check all these things mentioned.

It’s easier now than trying to diagnose an issue on the road. Screw it. I have all winter.

You guys seriously, thank you so much.
Chuck thanks for that “transmission checks for dummies” guide you wrote a few posts up


Sent from my iPhone using Tapatalk

Re: Transmission new and something ain’t right...

Posted: Sat Nov 02, 2019 6:53 pm
by Chuck Lutz
In my spreadsheet I have them listed at 0.751"

Here is a pic of several with different lengths and different "tits" on them.
Fourth From LEFT is .750.jpg
Fourth From LEFT is .750.jpg (78.76 KiB) Viewed 407 times
The tits have to fit neatly into the underside of the synchro sleeve.

( I believe Joel posted the length years ago...)

Re: Transmission new and something ain’t right...

Posted: Sat Nov 02, 2019 8:17 pm
by Joe Gopan
This is all I have handy for the 637832 T-84 Shifting plates

Length----0.831"---13/16"
Width-----0.219"----7/32"

This was taken from a NOS BW Synchronizer Assembly. The plates matched some used ones I saved. They are shorter than the falty plates that the jobbers have been sending.

Re: Transmission new and something ain’t right...

Posted: Sat Nov 09, 2019 11:23 am
by JeepdaddyRC
Update.
T-84 cover removed to inspect per suggestions.
Photos illustrate the results:
Photo 1: Blocking ring slop (play) is greater at 2nd gear (left) than 3rd gear (right).
Photos 2-4: There is visible play (0.22) between 2nd speed gear and mainshaft shoulder.
Bearings, 2nd speed gear, synchro hub and blocking rings replaced in recent rebuild.
However, I did not understand the multiple shim options at that time.
Could results 1 and 2 cause jumping out of second gear?
Time for shims?

Re: Transmission new and something ain’t right...

Posted: Sun Nov 10, 2019 9:01 am
by Wolfman
That is a lot of side play in second gear on the main shaft. Second gear, being a beveled gear, instead of a straight toothed spur gear is forced forward and backward as you are on the throttle and let off. Too much play, where you have the feeler gauge could be an issue. Second gear sliding for and aft too much as you are on and off the gas.
Shims in front of the synchro hub, between the hub & snap ring, will tighten up second gear clearance. Do this first.
Then shims between the oil slinger and spacer, in front of the rear main shaft bearing will tighten up the clearance of the 3rd gear baulking ring.

Re: Transmission new and something ain’t right...

Posted: Sun Nov 10, 2019 12:14 pm
by dpcd67
Twenty two thousandths is way too much play; you need to get to more like TWO thousandths. .002 inch is recommended.

Re: Transmission new and something ain’t right...

Posted: Sun Nov 10, 2019 12:27 pm
by dinof
Maybe shims are not the answer.....I bet the bronze bushing is worn and when inserting the feeler gauge it is cocking to the right and giving this reading. I would check both to see what's up.

Re: Transmission new and something ain’t right...

Posted: Sun Nov 10, 2019 2:58 pm
by Joe Gopan
Reminder;
2nd Gear Bushing I.D. must not be more than 1.129", if it is, the gear must be replaced with new, if you can get a bushing, it must be reamed 1.1275 to 1.1280" I.D..
Check the 2nd Gear Bearing surface on the mainshaft with a micrometer, if less than 1.126", replace the main shaft.