JamesC

iTrader: (5)

Check the first page for info on gear oil.

JamesC

Copperhead

OK, so now I've done a bit of roadracing, replaced the oil with Lucas dino oil, changed the pinion seal cause it was leaking. Found when racing that the diff seems to push oil out the pinion seal again. Can the vent be plugged? I've been unable to locate the white plastic vent mentioned in the FAQ, anyone have a photo of where it is? Since it's a press-fit, can it be changed or unplugged?

JamesC

iTrader: (5)

Yes, the vent could be plugged. Pressure then might force lube out the seals. The vent can be removed/changed. I've added info on location, which appears to change according to year, in the FAQ above.

JamesC

plemon90ta

iTrader: (1)

Thanks for the great info...

89_RS

What material are the tubes & center sections made out of? The front page tech article says to fully weld the tubes all the way around where they enter the housing. I can handle steels just fine, but if its steel to cast iron or iron to iron, I'm not capable of that.

quincy_806

The rear end just went out on my 92 z28 camaro, what other year model can i replace it with because i havent been able to find another 92 model?

JamesC

iTrader: (5)

Welcome to TGO, quincy. Any 9- or 10-bolt thirdgen. Check the first page for additional info on fourthgen rears.

JamesC

DoWork2day

I wonder if someone can say from experience, how much power a modified 10 bolt will handle, dragracing. I expect to have between 400-500 horsepower. And I understand the 9bolt is decent for a stock Camaro but beefing it up is limited. So would the housing or axles break, even if I put strong gears/splines etc?? Please help. Thanks.

SR-71

Standard 9-inch is stronger than a "beefed-up" 10-bolt. 10-bolt will handle 500 hp until you put on drag tires and start doing hard launches. Then it WILL break. The diff housing can't take it. No amount of "beefing up" can change that. Its diameter is too small so the torque forces get too high for the housing and gears.

I'm pushing 530 ft-lbs through my 10-bolt and it's doing fine, WITH STREET TIRES AND NEVER SEEING THE STRIP!

89_RS

Wrong. The ring gear diameter is the limiting factor here, not the housing. You can TIG weld the tubes of either a 9 or 10-bolt to the housing and both will still fail at around 500ft/lbs. The 9 bolt uses a 7.75" diameter ring gear. The 10 bolt uses a 7.5"/7.625" ring gear. You want a stronger rear, get something with a larger ring gear. BW just happened to use higher quality parts in the standard 9 bolt than GM did in there 10 bolt.

Ron U.S.M.C.

Edit = Double post

Ron U.S.M.C.

Are you using a support cover ?

SR-71

Actually, I was right. I said the same thing in different words. The diameter of the differential housing (not the case, which you were talking about) defines the size of the ring gear. Yeah I know-- semantics.

And then I misunderstood. Notice I said "9-inch," not "9 bolt." Oops.

SR-71

No. Even with the posi I don't have enough traction to allow the rear end to be shocked that hard. Street tires, no drag strips anymore.

89_RS

Ahh, sorry. My bad

plemon90ta

iTrader: (1)

http://www.s10forum.com/forum/f13/10-bolt-faq-129992/ Check out this link. Quite a bit of information. Good Luck, Patrick.

DoWork2day

thanks for these replies, just wanted to let you know I am working in the garage, was working all week so I haven't had time to get online and look at the s10 forum either, but I will. Thanks, I did see a looking to buy section on thirdgen.org also. I will look research all this further later today....

plemon90ta

iTrader: (1)

I got my 7.5 10 bolt with 28 spline axles and an eaton posi from a thirdgen member who had it in his camaro and was running 12.90 with mickey tomps. He did bust an axle and moved up to a moser 12 bolt. big bucks though, like 2200 and change. I;ve been beating the crap out of that 10 bolt and having a blast...

Fred meredith

Any one know if u can put a fourth gen ,third member in a third gen housing

SR-71

Actually the "third member" includes the housing. A good simple definition: "When all the internal differential parts are assembled into the gear case the finished unit is known as a third member." (http://www.offroaders.com/tech/Axle-Terminology.htm) The axles are the "second" members. The main axle case and axle tubes are the "first" member. There really is no "proper" third member in a 10-bolt. To see one, look at the pics here: http://www.metropartsmarket.com/rearend/products.html. A 10-bolt has the "third member," case, and axle tubes all in one piece.

If you're asking about putting the differential carrier from a 4th-gen into a 3rd-gen case, I did a quick perusal of aftermarket carriers on Summit Racing. The part numbers are all the same for 1988 and 1996 F-bodies. So the "short" answer to that question is, for 10-bolt to 10-bolt, yes. The carrier will fit the housing. BUT...

Depending on the year (like if yours is an earlier 3rd-gen), the axles may have a different number of splines, which means you may need to buy axles with the right number of splines that are the correct length.

But then I gotta ask, Why? If you have a 4th-gen rear end, just swap the whole thing. The extra inch or inch-and-a-half track width of the 4th-gen should improve the handling, depending on your wheel width and tire size. I know I could bolt a 4th-gen rear end into mine with no clearance problems at the fenders. Mine is a WS6 with the 245/50-R16 tires.

corvetteguy

iTrader: (1)

So question. I have a 10 bolt and I'm lookin at a limited slip that's set up for 28 splines. I was wonder if I have to modify my reared any to accommodate this, and of so how hard will it be? Also how do I tell if my rearend is a 7.5 or a 7.6?

ownor

iTrader: (5)

being an 86 rearend yours will probably be a 26 splines style unit. the only way you can use a 28 splined differential unit is to use axle shafts with 28 splines.
also... not only does it not make a difference about 7.5" or 7.625", but this is a sticky thread - read the first page!!!!111

.. and some more info is right there.

corvetteguy

iTrader: (1)

So I would pretty much have to change my whole rearend's internals to make this work?
https://www.thirdgen.org/forums/engi...burn-posi.html

SR-71

About all you could re-use from your old unit is the ring gear and pinion, if the "series" is the same. 3.08 and numerically lower are one series. 3.23 and numerically higher are the other series. There are a few aftermarket diff units that can fit either series.

Basically, you're replacing all the internals anyway. All the "internals" are basically three sets of parts: the differential unit and posi, the ring and pinion set, and the axles.

corvetteguy

iTrader: (1)

So the ring gear and pinion have nothing to do with the number of splines?

SR-71

That's correct.

The pinion connects to the driveshaft and engages the ring gear, which is mounted around the outside of the differential carrier.

The "splines" refer to the number of teeth cut in the end of the axle shafts, which engage the "side gears," which are inside the differential carrier.

Here's a pic I found. I marked in red, "Splines are here," to show where the splines connect the shaft to the side gears.

SanAntonio3

b

1983Chimaera

I currently have a '95 Z28 disc rear end with 2.73 gears and GM Posi-Trac in my '83 Z28. I want to know what is involved in swapping the 4th gen disc brakes and limited slip unit into an '89-up 3rd gen rear with shorter gears (3.08 - 3.42). Dealing with the extra width of the 4th gen and the limited selection of wheels available has gotten annoying, and if a modified 3rd gen rear will fix the problem and allow an easy way to have shorter gearing then it's worth sourcing a junkyard rear.

SR-71

The disc brake swap has been well covered here on thirdgen.org. Here is an article that outlines the process:
https://www.thirdgen.org/ls1reardisc

If you look in the various aftermarket parts catalogs for replacement carriers, you will see that the parts numbers are the same for 3rd and 4th gen cars. The only real difference between them is the axle length. So the whole carrier unit with the gears and posi unit are a direct bolt-in.

Swap in both the pinion and carrier unit (with new pinion seal and crush sleeve, of course), since they are already matched to each other. You will have to re-shim the carrier unit to be sure it is properly aligned with the pinion gears, the same as if you were doing any gear swap.

If your 3rd-gen unit is truly '89 or newer, then the axles will fit right in to the 4th-gen carrier.

1983Chimaera

Ok, so it's not a simple drop-in then, unlike a Ford rear end. I'm not looking to re-shim a rear end, I've read the process involved and I don't feel up to the task, otherwise I would live with the wider 4th gen rear and simply change gearing. I was looking to swap my disc brakes and limited slip to the 3rd gen rear to get the shorter width, but if it's that involved I'll stick with what I have.

Also, the link you provided details the swap for 98-02 rear brakes, how different are the LT1 (93-97) brakes?

JamesC

iTrader: (5)

The two systems, 89-97 and 98 up, are different designs. The latter is generally considered better, if for no other reason than the parking brake. There's a link in the info section of this thread detailing the 89-92 swap (89-97 are nearly identical).

JamesC

SR-71

Shimming the carrier isn't as bad as it looks in the instructions. Just takes patience.

If it were me, I'd put in the whole 4th-gen rear end, and it IS a simple bolt-in. The width difference is less than an inch. If your car is like most, it will have plenty of clearance. I've lowered my '88 Formula so it has only 4 inches ground clearance, and I've still got over 2 inches gap between the rear tires and the fender opening.

There are LOTS of wheels out there for 3rd- and 4th-gen cars. You just have to look. For instance, TireRack.com alone has 24 different wheel styles in 16", 17", and 18" diameters, for the 4th-gens. And 20 styles for 3rd's.

1983Chimaera

Obviously you misunderstand me...Currently INSTALLED IN MY CAR is a complete '95 Z28 rear end with 2.73 gearing, LT1 brakes and limited slip (and has been for the past 5 years). I am tired of having to run -19mm offset / 6.75" backspacing wheels on the rear, and would like to regain the original width of the 3rd gen rear so I can run the same wheels front and back without the need of spacers or adapters. I also do not want the 2.73 gearing I am currently stuck with, so if merely bolting my 93-97 LT1 brakes and installing the 4th gen limited slip into the 3rd gen carrier will work, it will solve all three of my problems, hence my interest.
As for wheel availability, I have looked over the styles offered for the 4th gen backspacing, and it is very limited. I have chrome 15 x 7 Cragar Quick Tricks on the front of my car, and would like to run the same or some Outlaw style wheels on the backs, but have been unable to find any offered with nearly the backspacing required for the 4th gen rear. On the rear I have a pair of late 4th gen silver 16" 5-spoke wheels. I do not want my wheels to stick out on the rear, and I want to have the ability to rotate my tires.
So again, my question is will the 93-97 brakes directly swap, without modification, to the 89-92 3rd gen rear, and will the limited slip directly install I.E. bolt it to the ring gear and go? I have done similar with Ford setups, namely installed SN-95 discs and limited slip from a '94 into an '88 Fox body rear end, and want to know if it is as simple on the GM cars. Also, is there a difference in overall width between the 89-92 rear ends and the 82-88 rears? What is the difference in width between the 89-92 and 4th gen if so?

SR-71

OK. Sorry. I misread your post. Now I'll try to answer in your world.

I dug deeper, and found that the 4th-gen rear end is 3 inches wider than the 3rd-gen, give or take a quarter inch.

There is no difference in the 3rd-gen axle widths from '82 to '92.

The brakes will swap, following the procedure outlined in the brake swap link I referenced. The main difference in the different 4th-gen brakes are the park brakes. The mounting process is the same. Sad to say, it's not just a bolt on swap. It requires modding the axle ends or using an aftermarket adapter kit.

You cannot put gears numerically higher than 3.08 on your 2.73 carrier, as there were two different carriers used: one for 3.08 and lower, and another for 3.23 and higher.

Even if you could put higher numeric gears on the carrier, you would still have to shim the carrier in the housing. Any time you swap gears and/or carriers, you have to go through the fitting and shimming process. Like I said, though, it looks a lot worse than it actually is.

So yes, your 4th gen posi carrier and pinion will fit in a 3rd gen housing, with shimming as I stated. But-- you are still stuck with gearing no more than 3.08. It's not a matter of fitting in the housing, but that the ring gears for 3.23 and up won't fit the carrier.

1983Chimaera

Ok, trying this once again;

I want to remove the '95 Z28 2.73 geared limited slip and rear disc brake equipped rear from my '83 Z28, and replace it with an '89-'92 28-spline axle 3rd gen rear already equipped with 3.08 - 3.42 gearing. I understand that swapping the '95 disc brakes will require modification (bummer, was hoping for a direct bolt on like a Ford 8.8 drum to disc conversion is), but will my '95 limited slip from the 4th gen 2.73 rear go directly into the 3.08 - 3.42 (or whatever other gearing the 3rd gen rear I eventually source ends up having) 3rd gen rear end without problem? In a Ford application it is a direct bolt in, no shimming required, so I'm really hoping GM didn't have cranium sphincterus when they designed theirs.

I'm not looking to tackle a ring and pinion change, I merely want to change the entire rear end to one already geared to my liking, and simply swap over the brakes and limited slip, if this is possible.

JamesC

iTrader: (5)

With the correct backing plates, the swap is a bolt-on. You might peruse the link I suggest above for pics and info.

JamesC

1983Chimaera

Yes, I saw that already, thank you, it's why I said I understand the brakes will require modification. I'm trying to get a straight answer on the rest of my original question, something I'm finding increasingly impossible on Thirdgen.org.

SR-71

I'll try one last time to answer what you need. (Honestly, I'm not usually this dense!)

Everything you want to do is possible, except possibly the limited slip. I don't know how limited slip is added to a Ford rear end, but I've been inside and rebuilt my 10-bolt posi.

In the GM 10-bolt, the limited slip is part of the differential carrier assembly. If it's an Auburn unit, the undersides of the side (axle) gears are cone shaped, and those cones fit down into matching "funnels" that are machined into the carrier. If it's an Eaton, the undersides of the side gears are machined to match a set of clutches, which engage a matching machined area in the differential carrier.

In both types, the differential carrier is specially machined to enable installation of the positraction system. It's internal parts are not interchangeable with parts from a plain "open" differential carrier. If the rear end you want to use has an "open differential" carrier, you can't just put the posi parts in it. To "swap over the limited slip," you must install a posi carrier, which means also swapping the ring gear, because the ring gear bolts to the carrier.

To summarize (and let's see if I've got it right):

• You presently have a '95 positraction with 2.73 gears.
• You want to end up with a 3rd gen positraction with numerically higher gears.
• You want to use the positraction unit (the differential carrier assembly) from your '95 in the 3rd gen rear.

Here are the facts about this swap:

• Your present '95 posi carrier with the 2.73 gear set on it WILL bolt in to a 3rd-gen rear.
• Your present '95 posi carrier can only be geared up as far as 3.08 using stock parts.
• To get 3.23 or numerically higher, you normally need a different carrier, because there were two "series" of carriers. However, you can get higher-numbered aftermarket gears that will fit this carrier. See Jeg's or Summit Racing.
• You cannot just "swap the limited-slip" as a sub-assembly of the differential carrier. You must swap the whole posi/gear/carrier assembly.
• No matter what you do, since you will be swapping the differential carrier, to do the job right you need to re-shim the carrier in the housing to be sure the gears mesh properly.

Sorry, but that's just how the 10-bolt is made. The engineers really didn't care what we had to go through to repair or modify the rear end. They designed it for factory productivity first.

1983Chimaera

THAT answers my question, thank you. Unfortunately, it puts me back at square one and means what I wanted to do isn't economically feasible for me.
My experience comes with Ford Trac-Loc limited slips, which are dirt simple to install or swap and are separate from the ring gears. Same goes with the Ford 8.8" rear ends, which share common design from '79 onwards thru the Fox platform and SN-95. I swapped an '88 Mustang GT 8.8" rear with limited slip, sans axles and brakes (was equipped with drums originally) into my '94 SN-95 Mustang Coupe which originally had an open-diff 7.5" rear. Both used the same spline axles, so they were a direct swap, and the older Fox drum rear had all the mounting brackets already for the later SN-95 disc brakes. It even had the mounting purchases for the rear quad shock setup, as did my '94 Coupe's body even tho it wasn't equipped with them. Ford tends to build their cars to one assembly line standard, and merely delete items from sub models. It makes for a more streamlined assembly process and a savings in costs, and is part of why the Mustang has always been more bang for the buck over the F-body. It also has the benefit of making modding quite easy.

SR-71

On the other hand, Ford never did believe in making parts from one engine fit another, or make transmission mountings universal, like GM. Which makes modding a pain in the butt. On a GM, you can put the heads from an '82 305 on a '76 400 (which I did on my build), but you can't (hardly) swap anything between a Ford 351M and a 351W. Or bolt a 428 into a car that originally had a 390. Or bolt an automatic from a '99 Ranger into an F-150, even though it's the "same" transmission. But I once installed a Muncie "rock crusher" from an SS Chevelle into a Vega GT, and it was a direct bolt-in!

Each make has their own advantages and disadvantages, which is why I'll never say Chevy is better than Ford, or Mustang better than Camaro, on any point.

As for Mustang "more bang for the buck" than F-Body, that's true on several points. But for me, the most important point is personal fit. I can't sit comfortably in a Mustang, no matter what you do to the seats. So on that point alone, for me, F-Body is better than Mustang.

1983Chimaera

Actually I find my '94 Mustang far more comfortable than my '83 Z28, even with '98 Z28 seats installed in it. The Mustang is far more ergonomically designed, and the ride is immensely less harsh and bone jarring.
As for parts swapping, you do of course remember that the Boss 302 was a 302 Windsor block with 351C heads? Or that ANY Windsor family engine can be swapped easily in the same car by simply changing motor mounts, that the FE family has a large amount of commonality and can be safely bored .120 over in most cases, or that the Fox 2.3L crossmember will accommodate any of the other available transmissions, in either single or dual hump versions, a well as shared bellhousing patterns across families?
On the other hand, the 2.8L and 3.1L engines share virtually nothing in common with the offered V8s in F-Bodies, and unlike GM Ford used ONE engine brand across all divisions...Which means you don't have to specify if when speaking of a 350 you mean a Chevy or Olds, when you mention a 400 if it's a lowly Chevy block or a revered Pontiac fire breathing demon. I give GM credit on the new LS series engines, but I also realize they used a lot of Ford ideas in it, such as the semi recessed crank (something Ford has gone to long before GM did). Both are guilty of at times being shortsighted in their thinking, and at other times "borrowing" from the guy down the street in Detroit.
As far as rear ends however, I have to give Ford credit. In this case Ford has the superior design.

SR-71

I'll give you that, for sure.

This whole "off topic" discussion just goes to show that what makes a make "best" to somebody is most often familiarity. I've worked on all makes and most models, and I prefer GM's. When you make me be honest about it, though, it's mostly because I pretty much know GM's inside out. I'm familiar with Fords, and will work on Mopars if I'm forced to.

"Borrowing from the other guy down the street." I've seen that. First example that jumps to mind-- When GM and Ford first came out with 4-speed autos, I was working as a mechanic at a Ford dealership. Ford was having problems with their "AOD," but they had orders to fill. So there were a bunch of Fords in that first year that came out with "repackaged" 700-R4's. Can't say how many. Just "a bunch."

Ah, well... back to topic. Good luck on your rear axle endeavors. Keep your eyes open and you'll find a posi 3rd gen with the ratio you want. I understand all about budget. My 'Bird is in the garage waiting patiently for the cash to do a proper paint job.

tango1112

I've learned a lot from this post, thanks greatly for starting it...

88IROConv

What are the torque specifications on the rear cover bolts? I need to know because I like to way over tighten things.

JamesC

iTrader: (5)

30 ft. lbs. crosswise pattern.

JamesC

88IROConv

Since my plug leaks no matter how tight it is, is it safe to use thread tape on it?

irocdls1

Does anyone know if an 89 disc brake porpotioning valve will work on a 91 disc brake rear end....????

JamesC

iTrader: (5)

I'd use a liquid thread sealant on the last few threads of the plug.

There are two 1LE valves: one with M1.0 tube nut threads, which fits early 89 down and one with M1.5 tube threads, which fits late 89 up. So it may or may not fit.

JamesC

Maverick H1L

iTrader: (8)

I have a quick question:

Anyone know the P/N for the case fill/inspection plug on the side of the diff housing? Mine hadn't been out in so long it wasn't funny. It is rusted pretty bad, so I couldn't use a usual square drive on it... Had to use locking pliers to get it out. Now I'm looking to replace it so I can actually get it out again at some point.

Or, failing the P/N, anyone know the thread size on the plug?

JamesC

iTrader: (5)

Hey, Maverick,

I added that info to the first page.

JamesC