12 Bolt Clanking and Whining

[splehigh]

I replaced the carrier in my 71 C10 with a posi unit out of a 70 Blazer. I used my old ring and pinion so all I did was swap my ring gear to the posi carrier. I used the original carrier shims to get the correct backlash.

Now I'm getting a clank while shifting gears and also a whine/grind when accellerating a decelerating. Last night I shimmed the ring gear closer to the pinion and eliminated some of the backlash but still have the same clanking and whining. If I shim the carrier any more I wont be able to get the C clip on the axel.

The gears seem to be meshing together correctly, but do you thing I need to shim the pinion back towards the ring gear more?

Also, I currently have 3:73 gears and would like to convert to 3:07. Does anyone have a set of 3:07 gears or want to swap?

Thanks guys!

[cdowns]

you should have read the service manual and done it correctly the first time// maybe 50% chance you haven't junked it

[splehigh]

I should have, but that would have been smart. Also I probably would have all the right tools like the depth gauge to set the pinion depth.

I doubt I ruined the gears since I only drive it about 500 feet.

Thanks for the advice though. :-)

[71tahoe]

Originally Posted by splehigh

I should have, but that would have been smart. Also I probably would have all the right tools like the depth gauge to set the pinion depth.

I doubt I ruined the gears since I only drive it about 500 feet.

Thanks for the advice though. :-)

500 ft is a half mile of gear travel with 3:73. The same shims would have gotten you close but they were mated to the carrier/ring combo and changing the carrier invalidated the shim arrangement.

[cdowns]

about all the vendors have the factory service manuals at very cheap prices(less than the cost of a rear grenaded end) you did at least know enough to used the gear additive for the posi right?

you'd need to start at square one from the book to set it up// loads of guys me included choose the dropoff and pickup method of rear rebuilding

[splehigh]

Originally Posted by cdowns

about all the vendors have the factory service manuals at very cheap prices(less than the cost of a rear grenaded end) you did at least know enough to used the gear additive for the posi right?

you'd need to start at square one from the book to set it up// loads of guys me included choose the dropoff and pickup method of rear rebuilding

I did know enough to use the additive, but are you saying that would make it clank and whine? I've heard that the clutches will sometimes chatter while turning without the additive but not while traveling straight.

I know most guys dont mess with differential setup but I also know a few guys that do it themselves. At least I am learning through this experience. I guess we will see if my learning experiance has cost me a set of gears or not. I will keep you posted.

Thank you all for the responses.

[Deggs]

I'll be doing the same shortly with an eaton posi I just picked up, so I'm interested in how this plays out.

I too was under the impression that should the carrier be the same dimensions you can just swap the ring gear and pop it back in, although I do intend to check the lash and follow a guide.

Sorry about your luck, I hope it's salvageable.

[splehigh]

Originally Posted by Deggs

I'll be doing the same shortly with an eaton posi I just picked up, so I'm interested in how this plays out.

I too was under the impression that should the carrier be the same dimensions you can just swap the ring gear and pop it back in, although I do intend to check the lash and follow a guide.

Sorry about your luck, I hope it's salvageable.

Thanks man. Yeah thats what I was told from several sources, but maybe it depends on how lucky you are.

I'm pretty sure my gears are ok. They dont look worn at all and there are no shavings in the fluid or housing. We will see...

[71meangreenc10]

Guys,
If you dont have the special tools to set up your backlash and pinion depth along with the right torque wrenches, leave the axles alone and take them to a shop. You will regret it........

If anyone is close to me, bring it over and I can help, done several have the tools.....


Smitty

Originally Posted by Deggs

I'll be doing the same shortly with an eaton posi I just picked up, so I'm interested in how this plays out.

I too was under the impression that should the carrier be the same dimensions you can just swap the ring gear and pop it back in, although I do intend to check the lash and follow a guide.

Sorry about your luck, I hope it's salvageable.

[Mike C]

The most difficult part of working on a rear is the pinion depth. A carrier swap is a good spot to start learning about diffs. The beauty of the swap you guys are talking about is that it does not require a pinion depth checker. A cheap magnetic base and dial indicator are the only special tools. The only special parts I would recommend is a universal side gear shim set.

The carrier should be a TIGHT fit back into the bearing caps. This is what sets preload on the side bearings. If your backlash is the same before and after, that should be spot on. If the carrier was tight when putting the shims and bearing races together. If it is loose, then when you put it in gear and apply a load the ring gear is going to try and walk away from the pinion which increases backlash which could be a source of noise.

But not much can "Clunk". I would check to make sure that you have the thrust washers underneath the spider gears and that there are no broken parts in the posi case. I would check that the u-joint is not bad and that the cap straps are tight.

But if you don't have a service manual, get one. Like I tell my 7 year old, "If you can read the book and do the math, you can do anything."

[splehigh]

Originally Posted by Mike C

The most difficult part of working on a rear is the pinion depth. A carrier swap is a good spot to start learning about diffs. The beauty of the swap you guys are talking about is that it does not require a pinion depth checker. A cheap magnetic base and dial indicator are the only special tools. The only special parts I would recommend is a universal side gear shim set.

The carrier should be a TIGHT fit back into the bearing caps. This is what sets preload on the side bearings. If your backlash is the same before and after, that should be spot on. If the carrier was tight when putting the shims and bearing races together. If it is loose, then when you put it in gear and apply a load the ring gear is going to try and walk away from the pinion which increases backlash which could be a source of noise.

But not much can "Clunk". I would check to make sure that you have the thrust washers underneath the spider gears and that there are no broken parts in the posi case. I would check that the u-joint is not bad and that the cap straps are tight.

But if you don't have a service manual, get one. Like I tell my 7 year old, "If you can read the book and do the math, you can do anything."

Thanks Mike! That is the kind of useful info I was looking for!

I'm almost certain I had the carrier shimmed tightly enough, but I'll double check that. As far as I can tell the posi unit is ok as well. I had the unit almost completely apart except for the clutches, and found no broken parts or anything.

My buddy that works at a transmission shop and has rebuilt several differentials is coming over tonight to take a look at it. Hopefuly he will be able to figure it out.

Thanks again!

[splehigh]

So here is what we found last night. The 3:08 posi carrier out of the 70 Blazer was wider than the 3:73 non posi from the 71. Hence the reason why I couldnt shim the carrier close enough to the pinion gear. There was about an 8th inch difference in width.

So what made the difference? Is the housing from the 70 blazer different, or is it because of the different gear ratio? Someone said that there are different series carriers for different ratios. I believe they said 3:73 is a 3 series and 3:08 is a 4 series.

So for now we just put the non posi 3:73 unit back in.

The plan is to save up for an Auburn posi and 3:08 gear set.

[cdowns]

different carriers for different ratios // factory service manual covers these important differences

do you know if you actually have a posi for a truck they are different than a car 12bolt as well as the different series for the ratio ranges

did you change the pinion? new crush sleeve? and preload?


if you really want a working posi maybe save and have a professional shop do it,your buddy with sperience and doesnt know about the different carriers well he dont know much

expect in the $1200-$1500 range for the RIGHT parts PROPERLY installed

[usmcchevy]

Originally Posted by splehigh

So here is what we found last night. The 3:08 posi carrier out of the 70 Blazer was wider than the 3:73 non posi from the 71. Hence the reason why I couldnt shim the carrier close enough to the pinion gear. There was about an 8th inch difference in width.

So what made the difference? Is the housing from the 70 blazer different, or is it because of the different gear ratio? Someone said that there are different series carriers for different ratios. I believe they said 3:73 is a 3 series and 3:08 is a 4 series.

So for now we just put the non posi 3:73 unit back in.

The plan is to save up for an Auburn posi and 3:08 gear set.

3.73 gears require a 4 series carrier
3.08 gears require a 3 series carrier

There are thick and thin gear sets available aftermarket to adapt different ratios. Why buy an aftermarket carrier?

[Mike C]

Yup. As noted above. The difference is about 1/4". You can buy a ring gear spacer for the 3 series carrier and make it work. Doesn't work the other way, though! Should come with all new bolts and lockwashers. Trucks break the carrier at different spot than cars. In trucks the 3.73 and up use a 4 series carrier (called that because for the most part uses 4 ratio gears: 4.10, 4.56, 4.88) Cars break at up to 3.90 and 4.10 and up. Get a spacer and go through the backlash setting process and you should be good.

[splehigh]

Originally Posted by Mike C

Yup. As noted above. The difference is about 1/4". You can buy a ring gear spacer for the 3 series carrier and make it work. Doesn't work the other way, though! Should come with all new bolts and lockwashers. Trucks break the carrier at different spot than cars. In trucks the 3.73 and up use a 4 series carrier (called that because for the most part uses 4 ratio gears: 4.10, 4.56, 4.88) Cars break at up to 3.90 and 4.10 and up. Get a spacer and go through the backlash setting process and you should be good.

Thanks for the info Mike!

I was told that spacers can cause problems and that they tend to flex and break the ring gear bolts.

Also I decided not to use the posi carrier because the spider gear bearings/washers were badly worn and kept falling out. I was told I should rebuild it and get all new spider gears.

[silver7]

Hey splehigh, I have a 43/14 ring ring/pinion (3.07 ratio) OEM tooth combo I'll trade with you for the 3.73 gears if your gears are from a 3 series carrier. My set looks to be in great shape. Also please verify the outer and inner diameter of your ring gear.

Mine

OD - 8.75"
ID - 5.4"

I attached a diagram which may help.

[splehigh]

Originally Posted by silver7

Hey splehigh, I have a 43/14 ring ring/pinion (3.07 ratio) OEM tooth combo I'll trade with you for the 3.73 gears if your gears are from a 3 series carrier. My set looks to be in great shape. Also please verify the outer and inner diameter of your ring gear.

Mine

OD - 8.75"
ID - 5.4"

I attached a diagram which may help.

I appreciate the offer Silver 7. I'm pretty sure my 3.73 gears are on a 4 series carrier.

I already put the 3.73s back in and plan on driving it like that for a while till I save up for a posi and possibly some 3.42 gears.

Thanks again

[silver7]

No problem and good luck.