Shift pattern 1981 8LL? transmission

[coastlogger]

Put a big load of rock on this afternoon and went for a shakedown cruise.To my annoyance discovered an issue with 3rd gear.Coming down a grade with jake on,quite low rpms,when i go to accelerate,sort of about when gear train stops holding truck back,itll jump out of 3rd gear. Didnt think to try and see if it does it without jake. Did try to get it to do this after i dumped load(empty truck) and could not make it do this,jake was on.

 

[DMiller]

Gonna hate this post, time to drag the whole box out as that no longer sounds detents but incorrect retainer(s) or broken snap rings on the mainshaft gears or bearings.

 

[coastlogger]

yes i think so. Will likely run it for a few loads avoiding problem gears then pull out over winter. Any tips on doing this without a real transmission jack?

 

[Birken Vogt]

Any tips on doing this without a real transmission jack?

Rent one for the day? That's what I do. Or find some hillbilly that will take it out for me and use my time to do work that pays better.

 

[DMiller]

Trans jack is a Necessity with these off balance square bottom trannies, especially to go back in. Want it square to the engine so the splines will align smoothly and you can get the fork across the release bearing assembly on the clutch. One note, adjust the clutch for the optimum freeplay PRIOR to removal of the trans, easier after to get back in.

 

[DMiller]

May be another issue here. Dawned on me as one of those OLD brain cells sitting in limbo decided to fire.

We had RT12513 Fullers in the late 80's with air lock outs for High Side on them, could use all but OD in 13th, also had a lockout once in High side would block highest gear as the trucks were geared they could run well over 85mph. May be such a lockout on this but doubtful, had a air poppet detent on the air valve side.

By the fact will jump out of 3rd and not go into 4th of the main box I still Highly suspect issues on the mainshaft. Continuing to run it may or may not do more serious internal damage, if not trying to lock up may be OK until a short time in future. If you need to tear this box apart and have never done one, take it to a shop, some special tools required although I have timed these standing on end in a Budd wheel, NOT Fun.

 

[coastlogger]

Its 5th that is missing,as far as I know its missing in all 3 ranges but I need to confirm that. Like i said it seems to try to engage grinding noise etc but wont go in. The jumping out thing is 3rd so I think thats a different sliding clutch no?Would 4 and 5 be on the same sliding clutch I think ?

 

[Shimmy1]

You have problems with the gears on the main shaft, as Dmiller has said. Third and fifth gears are right next to each other on the mainshaft. Fourth is direct, slider couples mainshaft directly to input shaft. Fifth is an overdrive gear. I used to drive a 1988 IH with an 8LL, had similar problems to yours. Mine started by slipping out of 5th, eventually would not stay in no matter what. Snap-rings and washers were gone, I guess this was a common problem for these transmissions.

 

[DMiller]

Common to most the older Fullers.
Is a allowed clearance where optional gear retainers thickness washers were used to take up SOME slack, slack got too bad they went into a self destruct mode eating themselves inside out. Most kits to rebearing and replace a few worn gears/sliders USED TO come with new retainers, I have not heard if still do.

 

[92U 3406]

Depending on how old this transmission is you may have a b***h of a time finding parts. When I did my 15615 I managed to get a complete Eaton bearing and seal kit. What I had trouble with was the fact that they had done some updates which required additional parts. My input shaft had wear so I ordered up the number that superceeded the shaft that I pulled out of it. Gear teeth didn't match the drive gear (super sloppy). Wanted to order the updated number for the drive gear but found the mainshaft key was updated from 3 sided (I think) to 6 sided. I had no idea if they would be cross-compatible and couldn't find anyone that could answer that. Didn't want to replace perfectly good mainshaft parts just for that. I did get lucky and found an aftermarket shaft that fit properly, saving a ton of headaches.

 

[DMiller]

Figure on gut and refill by that information. Replace anything with a updated p/n to keep the box functional and the return to store parts runs to a minimum.

 

[Truck Shop]

There are no snap rings on the main shaft except for rear auxiliary drive gear which holds the main shaft and rear bearing in place. There are spacing washers and limiting washers
between the gears locked in place by a triangular or oval key 10" long. If transmission is jumping out of gear #1 worn sliding clutches #2 gears worn where sliding clutch engages
#3 excessive main shaft end play #4 worn main shaft and limiting washers #4 broken main shaft key. If its an old box 156 series and down the main shaft limiting washers come
in different thickness to set co-axle clearance between the gears on the main shaft. NEVER set one up tight it will roast it. The later High Torque series 157 and up have a no burn
limiting washer {or no brain} the clearance is preset and all washers are the same.

If it's jumping out of gear the detent springs won't hold it, Forget about that helping it. It"s rebuild time or get a reman.
Rebuilding Eaton twin counter shaft transmissions is my game.

Truck Shop

 

[DMiller]

I was just thinking of the snap rings for the retainers in each gear, yes the rear bearing snap ring is about the only one on the main ring but the ones residing in each gear wear and once in awhile crack/float.

 

[Truck Shop]

Not to contradict anyone on this thread, but there are no snap rings holding the gears in place on the main shaft. That is done with the main shaft key that locks
each limiting washer and spacer in place which inturn holds the gears in place.

Truck Shop

 

[DMiller]

Not so much holding in place but were there not snap rings internal to each gear to keep them from floating? That retained the cogged washer that the assembly washer rode against?

 

[Truck Shop]

 

[Truck Shop]

 

[DMiller]

Memories of my Working days!! Was told by at least a dozen guys could not time a Fuller without the insert tools. Did just as you have there so many times.

 

[DMiller]

As I see on the table, gears with internal snap rings? snap ring grooves? This one is definitely newer than anything I ever built, has the oil cooling pump which was coming to favor as I got out of the garage.

 

[DMiller]

Early on would wire the sliders in neutral and stand the case up in a budd wheel, then install the main and time the shafts. Made life interesting.