Checking a 14 bolt differential

[britannic]

I had my propshaft balanced and new bearings fitted and whilst installing it checked the input to the rear 14 bolt diff. It's a 4.56 full float axle with detroit locker installed. I found the input yoke turns about 55 degrees before it stops in either direction. Also, there is about 1/32" of side to side/up and down play in the outer pinion bearing (as observed from outside the diff) when I move it.

It's not too noisy, but it's not quiet either, there's no oil leaks and the gear oil isn't black. The diff seems the same today as it did 10,000 miles ago.

Your opinions on whether I should get it rebuilt or not, or if I can wait till next spring, will be welcome.

Since it's such a heavy duty axle (3950lbs), I'm thinking it can probably wait, unless I start doing some heavy weight towing.

[patrick m.]

If the yoke has lateral movement, so does the pinion gear. That means that the ring and pinion tooth contact point is not as intended.
I believe i would check it out before more damage is done.
Most G.M. diffs use a "backlash" in the .008 - .012 range measured at the ring gear.
If i understand you correctly, you can turn the yoke 55 degrees? That sounds like too much to me.
Patrick.

[Dieselboy]

55 degrees is probably okay. The Detroit locker in the 14FF requires a lot of backlash in its setup. My rear end is the exact same way. I can turn the yoke about 1/8th of a turn before gears clank inside, and that's the way it has been since I got it back from the gear shop. I wouldn't have any worries there, but the other side to side play may be a cause for concern.

I don't set gears everyday, so I'm not an expert, but I can say that my axle does not have the side to side play after 35,000 miles. And many of those are spent on the trail making that Detroit earn its keep.

[britannic]

I spoke with a couple of Chevy experts today and they said, don't worry too much about the rotational play, but do something about the side to side.

They told me an unothodox trick is to first retorque the crush sleeve to the correct value and check the play, then apply an extra pound and recheck. They also said it should only take 2 or 3 extra pounds at the most to remove the play - any more would require opening up the diff and then getting it set up properly.

[Dieselboy]

Crush sleeve? One of the coolest things about the 14FF is that it doesn't use a crush sleeve like lighter duty models. I know that the 10, 12, and 14SF do, but unless something has changed recently the only adjustment up there on the pinion is the front pinion bearing. The adjustment is located behind the six bolt cover.

edit: spelling

[ 09-12-2003, 08:58 AM: Message edited by: Dieselboy ]

[Dieselboy]

Here's a good link for 14FF tech.

Priate 4x4 14FF bible

[britannic]

DieselBoy: how do you adjust it? Will it remove the side to side play? I couldn't find any info about the adjustment in the manuals I have, only that the pinion nut torque is 350ft/lbs and the force to turn the pinion when removed from the diff. is 5-15 inch/lbs for used bearings when the proper preload is reached.

Is it possible to remove the pinion assembly without removing the axles, carrier and ring gear?

[britannic]

DieselBoy, thanks for the link, it conveniently packages the two military manuals I have into a single file.

From what I can see, the pinion has two taper bearings that when given the appropriate preload should take up the slack. If it's possible to remove the pinion assembly without dismantling the rest of the diff., I'm going to set the preload and see if that removes the play.

[Dieselboy]

I do know that if you are able to remove the pinion, that discards your current gear setup and you will have to reset them, which does include removing the axle shafts.

I haven't had to deal with any problems in the axle yet, but my best recommendation is if you aren't able to get the results you are looking for with your current mode of attack, then find a good gear or manual transmission shop and have them take a look at it.

I'm sorry I don't have better answers for you, but this is outside my realm of expertise.

[britannic]

Well, I found time to complete the job on the diff today.

Shortly after purchasing the truck, I had the "stealership" replace the rear diff. pinion seal, because I didn't have a 350ft/lb torque wrench or the time available to repair it back then.

You can imagine my chagrin on discovering they hadn't tightened the pinion nut !!!! Now I know why the job was cheap, they forgot to perform the "$300.00" tightening procedure!?! It took fully 5 turns before it tightened! Now, there's no play and just a little movement as the pinion contacts the rings teeth. There's maybe 30 degrees of movement in the drive shaft as the locker's clutches engage.