Rear End Rebuild?

[79dentside]

So someone had done a rebuild on my rear end converting it from 3.42 to 4.10’s (Still an open carrier). When you would put the truck in gear it would BANG, found out it was slop in the spider gears From side to side. I put a mini spool in and the bang is completely gone. Problem that I still have is that I have a slight howl in my rear end at 45-50 mph. Both on and off the throttle, but there is a quick break in noise when letting off the throttle, but then comes back like a second later.

I’ve done u-joints, I’ve done wheel bearings, I have new fluid in the diff, I’ve also done synthetic fluid... I’m getting tired of hunting this faint noise. Pinion does not move up or down at all. I am kind of wondering if maybe it’s a pinion depth issue??? This issue has developed in the last 5 months or so. Gear set is new, bearings I assume are all new, but I don’t know. How should I pursue diagnosing this issue? Hoisted in the air with someone controlling the speed, the rear end is completely quiet, so I am really lost. Maybe it’s time to take the ratio back down to like a 3.42 again and have a shop do some bearing and set the pinion depth? I am very fearful of rebuilding the rear end myself, but if there is something that I can do apart from sending it to a shop, that is preferred. Thanks!

 

[ali_c20]

Have you checked pinion bearing preload, pinion depth and wear pattern? Wrong setup can cause noises, also lack of lubrication. Unfortunately it is a pain to check this stuff cause opening the diff, remove driveshaft etc.

This article contains a lot of usefull information.

https://fuelandfriction.com/weekend...ars are newly,result of worn carrier bearings.

 

[79dentside]

I’ve been looking for something like this for months, THANK YOU! So according to the site:

“If your gears are newly installed and still create a howling noise, double-check its preload and make sure that the teeth are properly aligned.”

I wonder if it’s a preload issue? Like I said, someone has done the gears. It didn’t howl very much when I bought it. I honestly thought I just had planetary gear noise in my 3 speed, but now I am thinking it was rear end the whole time and it’s just been getting slightly worse.

To be quite frank, I don’t understand the wear patterns. I understand why you look at it, but I don’t understand what makes a good wear pattern over a bad one. Here is a picture of my gear set after I brake cleaned the whole unit (that is why it looks all chalky), but you can see some wear on the ring gear indicated by the shiny spots. I’m not sure if that is a good pattern or not.

You must be registered for see images attach

You must be registered for see images attach

I’m not too worried about popping the cover if need be. The $30 in fluid hurts, but it’s not a pain to pop open. At this point, I’m getting fairly used to taking this thing apart haha.

My uneducated thinking for what it’s worth.... I am not leaning towards a bearing. Why I say that is because the noise happens in the accel and decel side of the gears BUT when I take my foot off the gas, there is about a 1/2 second point in time where the noise STOPS abruptly and then comes back on the deceleration phase. Now I’m no mechanic, nor do I know what the heck I’m talking about, but I would lean towards a bearing making a fairly consistent noise whether on the accel or decor side because the parts are still moving at the same speed. But I don’t know anything, just thinking.

 

[ali_c20]

This pdf has some good information.
https://eastcoastgearsupply.com/fil...ring-and-pinion-installation-instructions.pdf

The pinion seams to be too far away. To see the exact pattern using color would be good.

Quote from the pdf which helped me a lot when doing my first diff:

Reading the contact pattern is easy as long as I am not mislead or sidetracked. The
only part of the pattern that helps me set the pinion depth correctly is the contact
position with regards to the face and flank of the teeth. If the contact pattern appears to
be towards the heel or the toe of the ring gear teeth I pay no attention and look only at
the pattern position from face to flank. The pattern will also change from heel to toe
but in most cases an ideal heel to toe pattern can not be achieved. Trying to obtain a
pattern that is centered from heel to toe will usually lead to frustration and a noisy gear
set. Even if it does not seem intuitive or reasonable, I am only concerned with the
position of the pattern from face to flank. I have found that housing alignment and the
position of the pinion bearing bore in the housing affects the pattern from heel to toe and
can not be corrected without machine work. A contact pattern that is centered from face
to flank always indicates correct pinion depth even if a pattern that is centered from heel
to toe can not be obtained.

 

[79dentside]

Thank you @ali_c20 . You have been very helpful. Now let me ask this, sounds like a perfect alignment is very hard to get, should I be concerned and get this in the shop or is this something that is just going to make a little noise and not hurt any thing?

I am not comfortable doing such precise work on the rear unfortunately.

 

[Blue Ox]

I’ve been looking for something like this for months, THANK YOU! So according to the site:

“If your gears are newly installed and still create a howling noise, double-check its preload and make sure that the teeth are properly aligned.”

I wonder if it’s a preload issue? Like I said, someone has done the gears. It didn’t howl very much when I bought it. I honestly thought I just had planetary gear noise in my 3 speed, but now I am thinking it was rear end the whole time and it’s just been getting slightly worse.

To be quite frank, I don’t understand the wear patterns. I understand why you look at it, but I don’t understand what makes a good wear pattern over a bad one. Here is a picture of my gear set after I brake cleaned the whole unit (that is why it looks all chalky), but you can see some wear on the ring gear indicated by the shiny spots. I’m not sure if that is a good pattern or not.

You must be registered for see images attach

You must be registered for see images attach

I’m not too worried about popping the cover if need be. The $30 in fluid hurts, but it’s not a pain to pop open. At this point, I’m getting fairly used to taking this thing apart haha.

My uneducated thinking for what it’s worth.... I am not leaning towards a bearing. Why I say that is because the noise happens in the accel and decel side of the gears BUT when I take my foot off the gas, there is about a 1/2 second point in time where the noise STOPS abruptly and then comes back on the deceleration phase. Now I’m no mechanic, nor do I know what the heck I’m talking about, but I would lean towards a bearing making a fairly consistent noise whether on the accel or decor side because the parts are still moving at the same speed. But I don’t know anything, just thinking.

The bearing stops making noise the only time it isn't loaded, so you think it isn't the bearing?

Buy or borrow a dial indicator and some of the paste for patterning the teeth. Pull the cover off, clean up the teeth, measure the backlash and check the pattern. If that's all good you'll have to chase preload.

It would help to know which rear it is too.

Here's what the factory says you're looking for. The patterns are the same for all GM rears.

You must be registered for see images attach

 

[79dentside]

The bearing stops making noise the only time it isn't loaded, so you think it isn't the bearing?

Buy or borrow a dial indicator and some of the paste for patterning the teeth. Pull the cover off, clean up the teeth, measure the backlash and check the pattern. If that's all good you'll have to chase preload.

It would help to know which rear it is too.

Here's what the factory says you're looking for. The patterns are the same for all GM rears.

You must be registered for see images attach

Honestly, I don’t feel comfortable doing the work myself in this case so I am almost tempted to take it to a shop and have a new pinion bearing put in and the correct backlash (Depending in the cost). I tried to back the pinion nut off to do a pinion seal and my compressor wouldn’t budge that nut, let alone me with my breaker bar. I cannot get it off, therefore I would t be able to put it back where it’s at. There is too much torque on it.

The rear end is a 12 bolt out of my 1979 GMC “Heavy Half” Sierra 1500. I believe the gear set is like a 4.10 or 4.11, whatever someone would put in this. It had 3.42’s when it was stock.

 

[ali_c20]

Thank you @ali_c20 . You have been very helpful. Now let me ask this, sounds like a perfect alignment is very hard to get, should I be concerned and get this in the shop or is this something that is just going to make a little noise and not hurt any thing?

I am not comfortable doing such precise work on the rear unfortunately.

You're welcome.

I got my rear diff to a pattern that is in the middle between face and flank and more towards the heel. It doesn't make noises and the backlash is at the higher end of the tolerances. It took me ~4 hours to get there. Sometimes a gearset can make noises even when it's setup correct depends on the production accuracy, break in etc, but normally it should be quiet.

Maybe you can find a shop with a good reputation and ask how much they would charge for an alignment. The plus side would be that you have warranty if something goes wrong.

 

[MikeB]

I'm no expert, having done only three GM diffs, but I think your drive pattern looks OK from what I can see w/o marking compound. Coast pattern is something I don't worry about too much. If the drive pattern looks good, you don't want to compromise it trying to get a perfect coast pattern.

I've never had a "howling" problem with a GM 10- or 12-bolt diff, but some gear sets will do it even when brand new and properly set up. It's just the nature of the less expensive sets. In my experience, real GM gears and Yukon YK-series gears are very quiet. I hear Richmond and many others are not.

Your pictures show spider and side gears installed. But if it now has a mini-spool, you are asking for all kinds of differential wear problems on the street. And going around corners can be an adventure, especially in the rain.

 

[79dentside]

I'm no expert, having done only three GM diffs, but I think your drive pattern looks OK from what I can see w/o marking compound. Coast pattern is something I don't worry about too much. If the drive pattern looks good, you don't want to compromise it trying to get a perfect coast pattern.

I've never had a "howling" problem with a GM 10- or 12-bolt diff, but some gear sets will do it even when brand new and properly set up. It's just the nature of the less expensive sets. In my experience, real GM gears and Yukon YK-series gears are very quiet. I hear Richmond and many others are not.

Your pictures show spider and side gears installed. But if it now has a mini-spool, you are asking for all kinds of differential wear problems on the street. And going around corners can be an adventure, especially in the rain.

You are exactly right, I know that the mini spool isn’t the best option. The spiders were not aligned properly and would literally “BANG” into gear. You could hear it a few houses down with ease. Maybe I need to consider having a shop put in new spiders and the correct shims. There was just way too much slop in the spiders.

I wouldn’t doubt that the gear set is cheap, in fact, I would just assume it is. Based on everything I’ve seen in this truck, I can’t imagine the gear set is a prime unit lol. Maybe it is gear noise. I watched a video on YouTube of a guy who tore his new rear end apart and re-checked everything and it still made noise. Ended up being a noisy gear set too like what you mentioned. Bought a new set and the noise was gone.

It’s got steep gearing for a 3-speed. Turns around 3,500rpm @ 65mph. I really ought to consider maybe putting a stock set in it, which were 3.42’s in my particular truck.

You're welcome.

I got my rear diff to a pattern that is in the middle between face and flank and more towards the heel. It doesn't make noises and the backlash is at the higher end of the tolerances. It took me ~4 hours to get there. Sometimes a gearset can make noises even when it's setup correct depends on the production accuracy, break in etc, but normally it should be quiet.

Maybe you can find a shop with a good reputation and ask how much they would charge for an alignment. The plus side would be that you have warranty if something goes wrong.

This is kind of my same thinking. Someone did some work to the rear end and I would prefer it be dialed in so that I don’t have to worry about a rear going out.

Does anyone have a ballpark of what this might cost if I go to a shop? I know differential work gets expensive, especially when dealing with LSD and Posi, but I don’t have that.

 

[MikeB]

Does anyone have a ballpark of what this might cost if I go to a shop? I know differential work gets expensive, especially when dealing with LSD and Posi, but I don’t have that.

My only experience with a shop doing diff work is when a buddy of mine had his 77 Nova's gears replaced. In this case it was an 8.5" 10-bolt with 2.56 gears that he wanted to replace with 3.42 gears. He actually interviewed a few shops and found a guy who really knew what he was talking about.

The labor cost was around $600, as I recall, but the guy did an awesome job. He was perfectly fine with us watching for an hour or so, and didn't take any shortcuts. My buddy had already bought a Yukon YK-series R+P set and a new "2.73 up" case. The mechanic supplied Timken bearings, crush sleeve, shims, and pinion seal. Having done only one 10-bolt at the time, I learned a few things by watching him. That was 9-10 years ago, so I would expect that $600 is probably $750-$800 by now.

You should ask around and find a guy who can answer your questions about a truck 12-bolt. I'd ask him what brand gears he's had good luck with, and the pros and cons of using pinion spacers and shim instead of a crush sleeve to set up pinion bearing preload. Get him talking to see if he's done just a couple or a dozen or more. I like the guys who are knowledgeable, but not know-it-alls! Might also be a good time to replace wheel bearings and axle seals, if you haven't already.

 

[79dentside]

My only experience with a shop doing diff work is when a buddy of mine had his 77 Nova's gears replaced. In this case it was an 8.5" 10-bolt with 2.56 gears that he wanted to replace with 3.42 gears. He actually interviewed a few shops and found a guy who really knew what he was talking about.

The labor cost was around $600, as I recall, but the guy did an awesome job. He was perfectly fine with us watching for an hour or so, and didn't take any shortcuts. My buddy had already bought a Yukon YK-series R+P set and a new "2.73 up" case. The mechanic supplied Timken bearings, crush sleeve, shims, and pinion seal. Having done only one 10-bolt at the time, I learned a few things by watching him. That was 9-10 years ago, so I would expect that $600 is probably $750-$800 by now.

You should ask around and find a guy who can answer your questions about a truck 12-bolt. I'd ask him what brand gears he's had good luck with, and the pros and cons of using pinion spacers and shim instead of a crush sleeve to set up pinion bearing preload. Get him talking to see if he's done just a couple or a dozen or more. I like the guys who are knowledgeable, but not know-it-alls! Might also be a good time to replace wheel bearings and axle seals, if you haven't already.

GREAT info, thank you very much. Unfortunately I paid $1,450 for the truck, so I hate the idea of throwing almost $1,000 at it Haha. I will definitely do some talking around, see what I can find. Might as well throw a better gear set in. I would hate to have them set the backlash and pre-load and the noise be the dang gears the whole time.

 

[eskimomann209]

Backlash and pinion depth.
Howling From my experience is too loose. A whine is too tight.
but these aren’t rules just my experience. Taking apart a rear end that has a few thousand miles on it means you gotta set it up to where it was. Not to what’s “correct” so you need a prework pattern and the setup pattern needs to match it.
Once it whines and howls in new gears... if ran too long, odds are you’re going to have a hell of a time getting it to stop.
A slight whine on accel is accepted depending on fear quality. But should be quiet in coast. It also looks like the pattern is a little high on the heel to me but marking compound is what we really need to see

 

[MikeB]

GREAT info, thank you very much. Unfortunately I paid $1,450 for the truck, so I hate the idea of throwing almost $1,000 at it Haha.

Looks like you got what you paid for.

I don't know what else to suggest unless you can find a complete rear axle somewhere. I think just about anything from a 73-87 C10 should fit.

 

[79dentside]

Looks like you got what you paid for.

I don't know what else to suggest unless you can find a complete rear axle somewhere. I think just about anything from a 73-87 C10 should fit.

The truck has work done to it. It’s got a new motor, the tranny has a shift kit and the rear end had upgraded gears. Unfortunately, they howl ever so slightly at 45 mph. The truck is very solid, I am very happy with what I paid for it. It’s set up to be a sleeper, pretty much the bottom side up has been replaced or fixed.

This is just something that I will have to eat, cost wise.