Adjusting an old ring and pinion

[bushmechanic]

I'm about to pull a differential, and have encountered a question I never have before.

I want to re-use as much of the original stuff as possible, but what if it shows to have been worn in in a manner that's not ideal, or has a touch too much play?

Can I simply adjust the backlash and pinion depth to bring it where it needs to be, or will that produce too much heat or potentially crack teeth due to added stress?

All I've ever done is replace stuff with new or just put old stuff back set up the same way it was when it came out. Never had to think about this before.

 

[like2wheel]

I've tightened the backslash without a problem, but if you change the pinion depth, you'll likely get noise.
If it's quiet now, it's probably wearing correctly.

 

[kd3pc]

it depends on which make the rear is from....

some have a one time crush collar/washer/bearing holder and others you stack shims and add washers so the wear marks are even left to right an side to side. All that assumes the rear housing is still square and the axles true and are in good shape. Usually I replace axle bearings while in there, as well as the others.

Unless you have some really good calibrated finger tips, you will need some measuring tools.

 

[rjacobs]

Make sure to measure pinion break away with an inch lb torque wrench prior to disassembly...

Also measure EVERYTHING that you take out with a micrometer.

I have changed bearings and seals in a few different Jeep Dana 30 and 44 diff's and havent had any issues, but I measure everything as it comes out and put it back exactly the same way. Then run a pattern before buttoning it back up. My Jeep buddies have done the same numerous times also with no ill results.

 

[SGKent]

you start by measuring the backlash. Unless it is way off like trash city it should be set the same. The pinion should be the same depth too but without special tools that is near impossible to do. You can grease or dye the ring and spin it in both directions with a little resistance from your other hand, and then take good photos of the pattern. The pattern needs to be the same when you are done or it will sing.

 

[bushmechanic]

It's a 12 bolt axle. Everything else has been replaced or restored. I'm going in there to get to the carrier and pinion bearings because they ought to be changed to finish it off.

Sold my dial indicator, but I have another showing up on Friday. I can use other stuff, but that's the most convenient. It's easy to measure small amounts of torque without tools, though, so I'm not worried about getting those inch pounds right. No need for the wrench.

I guess my specific question is just whether or not I could remove a touch of backlash without actual damage, so long as it doesn't leave it's original contact area. I'm sure it would indeed be noisy for a while...

...but would it be terminally noisy?

 

[66cj225]

I'm going in there to get to the carrier and pinion bearings because they ought to be changed to finish it off.

If it hasn't seen race service or been abused; leave it alone if you don't have the specs and a way to measure them. GL90 was marvelous stuff.

 

[greg13]

If it ain't broke, don't fix it!!!

 

[SGKent]

when you change the lash it may sing. How do you know what the factory lash was new? When you replace the bearings, the play may be in the bearings. As for "awhile," noisy is probably the next 100,000 miles.

 

[bushmechanic]

I'm going in there to get to the carrier and pinion bearings because they ought to be changed to finish it off.

If it hasn't seen race service or been abused; leave it alone if you don't have the specs and a way to measure them. GL90 was marvelous stuff.

I'll have the specs it's at right now when I measure it all, as well as the GM specs. Just not going to bother with it until the gauge shows up.

 

[bushmechanic]

when you change the lash it may sing. How do you know what the factory lash was new? When you replace the bearings, the play may be in the bearings. As for "awhile," noisy is probably the next 100,000 miles.

About all I can do within reason is examine the wear pattern. I'm sure it can be traced back in some way, but I'm certainly not going to bother.

Hell, the thing might be fine. It feels fine.

Even so, the bearings are coming out. There isn't really a need to do it, but I got to having so much fun messing around with the axle that it's turned out pretty nice.

If I don't replace those bearings, it'll bug me until the end of my days. I just don't want to replace the ring and pinion. Not trying to save a buck; just trying to save as much of an axle as possible.

Your comment on the noise is part of what I'm looking to find out. How long would it take to break in, and would it break in or just plain break? I don't know the strength of those parts.

I figured that if it was too far out, it might actually build up too much heat.

It's not really my first rodeo, but I've certainly never deliberately taken an old differential out of adjustment once broken in before; not even in the middle of nowhere.

Seemed like something that would be worth exploring, since I'd never thought about it before.

 

[no704]

Sounds like u got this!

 

[CraigStu]

I wouldn't worry about the backlash unless it is way out of spec now. If it's in spec, even if on the high end of spec, I'd replace those bearings and put the pinion back exactly as it was. Then put the backlash back exactly as it was.

 

[Chevy-SS]

Hey, for you rear end experts, I've got a 2010 Roush Mustang with 20k miles on its 8.8 rear end that howls a little bit, under light load, starting at about 35mph. Using dial indicator, I carefully measured backlash, and it seems to be about .020", while the specs call for .008" to .012". So I've basically got twice as much backlash as spec.

Is there a good chance I'd get rid of the howl by simply correcting the backlash, or would I be best to overhaul the whole unit??

Thank, Dave F.

 

[sberry]

What is the application? Something you are gonna run the **** out of cross country? If it's utility and working clean it out and put some new sauce in.

 

[bushmechanic]

What is the application? Something you are gonna run the **** out of cross country? If it's utility and working clean it out and put some new sauce in.

I'm just doing a good job rebuilding things on a car that are in my wheelhouse.

Picked the axle up out of a scrapped '66 GM full size, all original. It cost about $400, which I figured was a darn good deal, and the 12 bolt rear is a value add for someone down the line, and it's appropriate for the vehicle.

It's just funny I've never even considered that before. It was always either put it back in like it came out so it doesn't make noise, or replace the ring and pinion; common practice.

I just wanted to keep this axle on the road with as many original parts as possible. I like to save things when I think they've held up for a very long time.

 

[bushmechanic]

Sounds like u got this!

Yeah, I think I got the answers I needed, which collectively suggest:

"Don't do that, dumb-***".

Bit of curiosity removed, there. I just plain wasn't sure if it made any sense at all.

 

[bushmechanic]

I wouldn't worry about the backlash unless it is way out of spec now. If it's in spec, even if on the high end of spec, I'd replace those bearings and put the pinion back exactly as it was. Then put the backlash back exactly as it was.

That's what I'll do.

 

[CraigStu]

Hey, for you rear end experts, I've got a 2010 Roush Mustang with 20k miles on its 8.8 rear end that howls a little bit, under light load, starting at about 35mph. Using dial indicator, I carefully measured backlash, and it seems to be about .020", while the specs call for .008" to .012". So I've basically got twice as much backlash as spec.

Is there a good chance I'd get rid of the howl by simply correcting the backlash, or would I be best to overhaul the whole unit??

Thank, Dave F.

You can try reducing backlash by moving the ring gear. On the 8.8 the shims are under the bearing caps. Pull axles, pull caps, pull the center section, and be sure you don't mix up the shims for left and right sides. I would buy a selection of the shims because the factory tends to use a thick one and maybe a couple of thin ones. You will want to move the ring gear a few thousandths, so need to reduce total thickness of one side by say, .005" and increase the other side by the same .005". The OE shim stacks don't usually work out to well trying to make tiny changes. Moving the ring gear is pretty easy to do so it's worth giving it a try. Changing pinion height is a bear and you should have a pretty specialized tool to measure it. If getting backlash doesn't do the job I would buy new gears. Be sure to buy only Ford OE gears. A high % of the time you can move the old pinion shim to the new pinion and be good to go. Be aware though the pinion shim is between the gear and the bearing so the bearing closest to the gear needs to come off and that requires a press w/ the proper tool to grab the bearing. I did mine once to change the ratio. I borrowed the tools to measure the pinion (along w/ a bearing that had been opened up on the ID so it was now a slip fit to use for the measuring process) and it turned out that the OE shim was perfect.

 

[LS6 Tommy]

My experience is that most r&p that were out of tolerance were worn enough that they warranted replacement. It certainly couldn't hurt to try.

Tommy

 

[bushmechanic]

You can try reducing backlash by moving the ring gear. On the 8.8 the shims are under the bearing caps. Pull axles, pull caps, pull the center section, and be sure you don't mix up the shims for left and right sides. I would buy a selection of the shims because the factory tends to use a thick one and maybe a couple of thin ones. You will want to move the ring gear a few thousandths, so need to reduce total thickness of one side by say, .005" and increase the other side by the same .005". The OE shim stacks don't usually work out to well trying to make tiny changes. Moving the ring gear is pretty easy to do so it's worth giving it a try. Changing pinion height is a bear and you should have a pretty specialized tool to measure it. If getting backlash doesn't do the job I would buy new gears. Be sure to buy only Ford OE gears. A high % of the time you can move the old pinion shim to the new pinion and be good to go. Be aware though the pinion shim is between the gear and the bearing so the bearing closest to the gear needs to come off and that requires a press w/ the proper tool to grab the bearing. I did mine once to change the ratio. I borrowed the tools to measure the pinion (along w/ a bearing that had been opened up on the ID so it was now a slip fit to use for the measuring process) and it turned out that the OE shim was perfect.

Sorry, it's a 12 bolt GM.

I bought a whole kit that came with all the stuff I'll need.

Showed up today.

Usually I'd go piece by piece to get more choice, but this actually included good stuff, and it was relatively cheap. Even includes the crush sleeve and a bunch of shims for everything if it turns out you need them.

Got lucky with the ratio. It's 3.31, which is essentially what I'd put in there anyway.

Measuring pinion height can be accomplished with what I have, and inch pounds for that crush sleeve can be measured easily with a stick and a weight.

I don't have all the specialist tools, but I can "Egyptian" my way through it easily with just as much precision. We didn't always have those tools, after all; and we've been building this stuff for centuries.

Differentials are relatively new, but the parts inside them aren't.

 

[bushmechanic]

My experience is that most r&p that were out of tolerance were worn enough that they warranted replacement. It certainly couldn't hurt to try.

Tommy

Yeah, that's what I'd normally do, and probably will here.

I still want to have some fun investigating it, though. I can always bring it back the way it was before installation.

 

[CraigStu]

On one diff I should have measured the pinion preload but didn't have the tool. So I spun it by hand before disassembling it. Going back together I kept spinning it by hand until it felt the same as before. Worked fine.

 

[bigdav160]

Stay with the original pinion shim. No part replacement changes that dimension with exception of a mis machined pinion gear (and it should be marked). Put the backlash in spec. If you're just replacing bearings there isn't any reason to change those settings.

 

[bushmechanic]

Stay with the original pinion shim. No part replacement changes that dimension with exception of a mis machined pinion gear (and it should be marked). Put the backlash in spec. If you're just replacing bearings there isn't any reason to change those settings.

Yeah, sounds like the smart move.

I'm excited to have this one done, and I had so much fun doing restoring an axle off a car for once that I might just buy another and do it again.

Big difference from laying under a vehicle in a mud puddle somewhere. Now I know why people actually seem to enjoy it.

 

[Chevy-SS]

You can try reducing backlash by moving the ring gear. On the 8.8 the shims are under the bearing caps. Pull axles, pull caps, pull the center section, and be sure you don't mix up the shims for left and right sides. I would buy a selection of the shims because the factory tends to use a thick one and maybe a couple of thin ones. You will want to move the ring gear a few thousandths, so need to reduce total thickness of one side by say, .005" and increase the other side by the same .005". The OE shim stacks don't usually work out to well trying to make tiny changes. Moving the ring gear is pretty easy to do so it's worth giving it a try. Changing pinion height is a bear and you should have a pretty specialized tool to measure it. If getting backlash doesn't do the job I would buy new gears. Be sure to buy only Ford OE gears. A high % of the time you can move the old pinion shim to the new pinion and be good to go. Be aware though the pinion shim is between the gear and the bearing so the bearing closest to the gear needs to come off and that requires a press w/ the proper tool to grab the bearing. I did mine once to change the ratio. I borrowed the tools to measure the pinion (along w/ a bearing that had been opened up on the ID so it was now a slip fit to use for the measuring process) and it turned out that the OE shim was perfect.

Thanks Stu! I have a press and might even have the adapter to press off the pinion parts, but I want to avoid all that if possible. I think I will give it a try, your way. I'll but a shim kit and move the ring gear over to get .010" backlash.

Which backlash setting would be best.... .008" or .010" or .012" for quiet operation????"

Thanks again, Dave F.

 

[Chevy-SS]

Sorry, it's a 12 bolt GM.

I bought a whole kit that came with all the stuff I'll need.

Showed up today.

Usually I'd go piece by piece to get more choice, but this actually included good stuff, and it was relatively cheap. Even includes the crush sleeve and a bunch of shims for everything if it turns out you need them.

Got lucky with the ratio. It's 3.31, which is essentially what I'd put in there anyway.

Measuring pinion height can be accomplished with what I have, and inch pounds for that crush sleeve can be measured easily with a stick and a weight.

I don't have all the specialist tools, but I can "Egyptian" my way through it easily with just as much precision. We didn't always have those tools, after all; and we've been building this stuff for centuries.

Differentials are relatively new, but the parts inside them aren't.

Hey man, sorry for the confusion, but that guy was posting in response to a question I had posed on a Ford 8.8 rear. I wasn't trying to hijack your thread. It seemed like you had your answers, so I figured I would toss in a quick question, figuring there were already a few rear end guys in here. My apologies.................. Dave F.

 

[bushmechanic]

Hey man, sorry for the confusion, but that guy was posting in response to a question I had posed on a Ford 8.8 rear. I wasn't trying to hijack your thread. It seemed like you had your answers, so I figured I would toss in a quick question, figuring there were already a few rear end guys in here. My apologies.................. Dave F.

No worries.

 

[bushmechanic]

Well, it turns out that as-is, backlash is right about .008.

I was expecting more. Sweet.

From what I understand, the car was low mileage, so I guess that tracks, but that's still pretty damned nice.

 

[like2wheel]

Well, it turns out that as-is, backlash is right about .008.

I was expecting more. Sweet.

From what I understand, the car was low mileage, so I guess that tracks, but that's still pretty damned nice.

Low mileage?
I would put new seals in it & call it good.

If it ain't broke, don't fix it.


.

 

[bushmechanic]

Low mileage?
I would put new seals in it & call it good.

If it ain't broke, don't fix it.


.

Oh, I'm gonna fix it until it's broke.

One of the pinion bearings didn't feel quite right, and given the seal was leaking so bad it might as well have not been there, I think it suffered a bit of atmospheric ingress over time while the car sat wherever it was.

Didn't believe the statement that it was a low-mileage axle until I really started digging around.

Seems it's not worn out at all; just old and left under a car for a very long time.

This thing will be right as rain for another 50 years, and that's really all I wanted out of it.

 

[greg13]

If you had a seal leaking, make sure you check the vent. I have had plugged vents that cause the seal to leak, the pressure has to somewhere.

 

[HenryAZ]

Oh, I'm gonna fix it until it's broke.

If for no other reason than curiosity, I would use some gear paint on 4-5 teeth of each gear to check the contact points. This confirms pinion depth and other factors as being ideal.



GM Gear Marking Compound

 

[bushmechanic]

If you had a seal leaking, make sure you check the vent. I have had plugged vents that cause the seal to leak, the pressure has to somewhere.

I've installed a new vent. That was the last little external touch before I moved to the inside of the pumpkin itself beyond previous cleaning. The old one was damaged previously or during delivery; but I'd have swapped it anyway.

The other bearings and seals are done, and I've actually got a new seal on the pinion right now, but obviously I'll be replacing it after this. I only put it in there to finish things up and check for casting issues and leaks.

I considered just rolling with it as-is, but I can't bring myself to do it.

 

[bushmechanic]

If for no other reason than curiosity, I would use some gear paint on 4-5 teeth of each gear to check the contact points. This confirms pinion depth and other factors as being ideal.



GM Gear Marking Compound

Yeah, I'm going to do that before I pull it out. I'm certainly curious.

 

[like2wheel]

No need to paint the gears before you pull it out, the wear pattern will be obvious after 40k.
The paint is for after reassembly.

 

[Old School]

Ok, so you just want to freshen up the bearings and seals without changing the R&P, right?

1. If you don't know if the rear end made noise before, then don't mess with pinion depth.
2. Before getting anything out, mark one of the bearing caps, they are not interchangeable!
3. Don't worry about brake away torque, as you'll be changing the bearings and the crush sleeve anyway.
4. DO USE the marking compound before disassembly, see first remark, but you can't tell if new bearings won't change the depth/pattern. Then you want to bring it back to last known, working pattern.
5. Establish pinion bearing drag without the crush sleeve until final assembly.
6. Use sealer on the inside of the YOKE (not the pinion) this way you will push out excessive sealer out instead of in.
7. Use loc-tite on ring bolts and pinion nut.