Hi everyone - I'm new here. Not to forums or wrenching. I own a busy 5 bays shop specializing in Subarus and other imports. Anyway I have a project 86 Trans Am and decided to change my final drive from the factory 2.77 to 3.70.

I started out with a "rebuilt" 3-series carrier from 9bolt.com. It lasted about 2500 miles (wouldn't say it actually "lasted" at all though) before the carrier cones disintegrated into
a large amount of cast iron slurry. This was behind a stock TPI 305 and a slipping automatic. I'll post about that experience in another section on the forum. "Glenn" won't respond to my emails....

I got a Torsen (Eaton Truetrac knock off) carrier from Supa F Spares in Australia and it dropped right in with just minor clearancing of the pinion head. This thing absolutely rocks. I couldn't be happier. This carrier is a product they sell for Holden Commodores and Nissan Skylines in Australia. It's sold under their "Torqueline" differential brand:

https://supafspares.supplies/torqueline-differential/

Dave at Supa F was extremely helpful and the shipping was fast. The carrier was at my door in about 4 days via DHL. Total cost shipped was $530 USD. They accept PayPal. Contact Dave to get one:

Dave@supafspares.com.au

I'll post some pics up here in a bit. I didn't take many as I was in a hurry to get that rebuilt 3 series from 9bolt.com out of there along with the silver paint it filled my axle with. At any rate it's just a carrier install we have all seen it before. Nothing unusual about it.

This was an excellent way to get a proper Truetrac without spending a fortune on a new 8.8 or 9" that I don't need. The Australian guys runs these behind 500 HP RB30DET's with blowers. The 7.75 9 bolt is actually quite strong. When I tore down the 2.77 after 150k miles and 30 years it showed no wear whatsoever. I didn't even change the wheel bearings. With the Torsen carrier, the Yukon 370 gears, and a selection of bearings, shims, seals, etc from Ratech, the cost was around $1,000 in parts. That's about 1/3 to 1/4 of the cost of an 8.8 from Hawks when you figure adding a truetrac, brakes, shipping, etc. Even if you buy tools and have to learn R&P setup it's much cheaper and worth the learning experience.

Here's a shot comparing the original tooth profile to how much I had to remove to clear the new carrier. Ithe was about 1/8" off the tips of the teeth. It's nowhere near where they mesh. I used a die grinder with a cut off wheel to carefully round off the corners.




Rick

 

That's great! Do the 3.70's make a lot of noise?

 

They whine a bit under part throttle cruise as everyone mentions. I spent a lot of time on the setup and used a pinion depth gauge. I verified my carrier bearing caps were truly centered on the pockets, etc. My break in pattern is excellent - perfectly centered heel to toe. My backlash is .009". Many people say these gear sets make noise and I was even told by Glenn at 9bolt.com that his experiences have been the same. Sometimes people get lucky and get a set that doesn't make any noise.

In my research I came across quite a few references to the 5th generation Camaro's making similar noises from 390 and 410 gears and people being told by the service department that this is normal and that if they attempt to correct it the outcome may be worse than what it is now.

After putting 2500 miles on the gearset and seeing no wear at all to the gears despite being bathed in ground up cast iron slurry (almost a lubricant ) I'm not concerned with the whine in the least. It's not annoying to me - I don't have stock exhaust or intake and most days the radio is up.

Rick

 

Awesome!

I'm glad I could inspire someone else to decide to keep their 9-bolt axle but also get rid of the horrible stock, quickly failing "friction cone" LSD that makes the gear oil become a bearing-killing mess filled with metal flakes...

How did you solve the shimming of the carrier, did you use the same method as I did with the adjustable spacers or did you come up with something else?

 

I ordered my carrier bearing set and shims from Ratech:

http://www.ratechmfg.com/pop_up_order%209024.htm

And:

http://www.ratechmfg.com/pop_up_order%201145.htm

These are the factory correct part numbers. So it just went together with no troubles at all. I had to change one shim on my carrier to a slightly thinner one than what I had on the cone type carrier and it went right back to the .009" backlash that I had it set for on the previous carrier.

I think your supplier has a cataloging error or something. The bearings Ratech sells are Koyo Japanese bearings and they sold me the LM102911 cups..... I don't know why they showed a different cup at your parts houses.

Rick

 

Great to hear

I think you're right! I just checked the sites of the swedish supplier (Hansen Racing) and Rockauto..

Hansen Racing only shows LM102910 cups in their catalogue, but Rockauto has both. -910 from National Seal and -911 from SKF. Hansen Racing sells National Seal parts so that is probably why I got the wrong ones.

I still don't understand why Rockauto also lists the LM102910 cup for a Borg Warner 7.75" ??

These two entries are copy-pasted from Rockauto:

NATIONAL LM102910 Wheel Race; Outer Diameter=2.891", Length=0.62", Radius=0.031" Info
Rear; Borg-Warner M78; 7.75" R.G.

SKF LM102911 {#52069916AA} CUP Info
Rear; 7.75'' Ring Gear: (Only 1 Remaining)

edit: never mind! I just found out why, the LM102910 is listed at Rockauto as a "Wheel Race"! At Hansen Racing's website it is listed as a "Outer bearing race for differential bearing". So they have probably made a mistake when they translated the despcription to Swedish...

 

Ok that makes sense. I didn't look at the wheel bearing cup closely but they did slip out and they were definitely thinner like that.

My only concern would be the angle of the cup taper and how it mates to the cone. It's probably fine but I would be looking at bearing specs to see if they were the same. If it's been running this long though I'm sure it's fine.

Rick

 

after reading this I'm kind of tempted to do the same thing to my 9bolt. anyone have a complete parts list including specialty tools?

 

Besides the Torsen carrier listed in the first post (contact Dave at Supa F Spares), you will need:

Everything listed in the GM 7.75 row of this page:

http://www.ratechmfg.com/gmstandard.htm. (click on part numbers)

In addition, there are some 9 bolt rears that use a smaller pinion head bearing. Mine was one of these (86 Trans Am). It is a Ratech part number 8002 (or Timken set 67):

http://www.ratechmfg.com/pop_up_order%208002.htm

They also have a "compete kit" but it doesn't include the smart sleeve (their improved crush sleeve design) and it doesn't have the HM88610/HM88649 (8002) small pinion head bearing (if you have this style) so you would want to call them and order that if you plan to get it done in a day without first taking it apart to see which pinion head bearing it has:

http://www.ratechmfg.com/pop_up_order%20332K.htm

You will need a pinion depth gauge. I got this one (US made) - they have this auction up all the time and I just bid the $100 and waited for the auction to end. No one bid against me so the cost was $120 shipped:

http://www.ebay.com/itm/PINION-DEPTH...-/232286784422

And you will need a DIAL indicator inch pounds torque wrench for setting pinion preload. I got this one (CDI is owned by Snap On):

https://www.zoro.com/cdi-torque-prod...Q&gclsrc=aw.ds

You can optionally do wheel bearings. These are pressed onto the axles and can be done later pretty easily. Mine were fine so I put them back in. Axle bearings and seals on this page:

http://www.ratechmfg.com/gmaxlebear.htm

Rick

 

Bumping this because it's worth it. Thank you GeneralDisorder and KeyKey for the work and info, it's greatly appreciated!

At the time of posting this, I've successfully completed the swap on my 9 bolt. I was looking at needing to replace the rear end, wanting to avoid the poor excuses that are the replacement posi cones these days, but the budget needed to fix other things on the car as well this season. Being able to keep the 9 bolt saved a fairly decent amount of unsprung weight, which is always a bonus.

I was able to reach out to SupaF without issue and had the diff within a week, shipped from Holden country, with a wonderful 70% exchange rate. Can't hardly buy a TrueTrac in the States for the same price.

As expected, my cones were grinding themselves into oblivion after the UMI Autocross Challenge, so I had a wonderful slurry to deal with cleaning out of the rear end. The swap with without issue, as of this time. I have a 3.27 rear and I'm not so sure the thing wouldn't clear without shaving the pinion head, but I did it anyway. The diff nearly went back in with the shims I pulled out, but we ended up going down just a literal hair on the driver side. This put my backlash around .008" which is where it was when I pulled the old one out on a remarkable wear pattern. Keep in mind, this is a 200k+ mile rear BEFORE I got the car and I've beat on it successfully for 3 seasons. My steering box is shot and I just got a replacement in from TurnOne, so the diff doesn't have many miles yet, but the 10 or so we've put on it yielded great results.

Again, thank you all for taking your time and effort to R&R these rears! I hope someone else finds this as helpful as I did.

 

That's great! This is THE best option for the 9 Bolt. I finished this swap 2 years ago on my daily driver and it's going strong. Two-wheel peel everywhere I go.

GD

 

so you would recommend this gd? i have a parts car in my garage that im about to get rid of with a 3.27 9 bolt
and was undecided if i should keep it and build it for my 86 t/a .this sounds like the way to go!!!

sorry about the rant before,my apologies i see you are a busy man!!!
i may have questions about the swap at a later time

 

Yes I would absolutely recommend it! Other than the 3.70 Motive gears being a bit loud, the Torsen carrier has been absolutely excellent. It operates exactly as promised. Just like an open diff under normal driving, and when you launch the car both wheels burn rubber. It's a perfect transition with no noises or fuss.

GD

 

thanks,that's my plan then.(add it to the ever increasing list of "to do" items)

im assuming this rear will stand up a little better than a 10 bolt will to some increased horsepower and torque

 

The 9 Bolt is at least as strong as the LS1 equipped 10 bolt cars. 28 spline axles, etc.

GD

 

I've been running 424 hp to the rear tires for over 6 years with 3.70 gears and the stock 3 series carrier rebuilt in my 9 bolt, and it's still holding great with 2 tire posi paving asphalt. The 9 bolt will handle most anything you throw at it if it's set up properly. http://9bolt.com/faq.html Has some interesting info to digest.

 

im starting to have some confidence in the potential of this rear end.i used to have a L98 iroc(1987) with the same rear plus the 700r4 and a corvette servo(i paid $700 for the car,it was for parts as well but i drove it daily for 3-4 months due to a mto strike at the time)and it would get unlimited rubber and easily chirp in all three gears and sometimes a little bark into 4th.im hoping i can emulate that experience with my new enhanced L98(or the L31,STILL 100% undecided) by adding vortec heads,a baby LT4 cam plus a vortec specific edlebrock rpm and a holley 650 double pumper and some hooker shorty headers.my only other question is do i swap my t5 to my new engine build or do i just skip that and put in the 700r4 and throw in a corvette servo and freshen it up.i cant decide but would love to keep the stick,just afraid its days will be numbered

 

i dig your car friend,i usually hate that hood but its working on your iroc and looks sick truly!!was it a nightmare to get your tpi to work with that setup?

im at a crossroads now :do i go efi/tpi as i have a complete L98 and everything that goes with it(my car is a stock carbed lg4 t5)
and i also have vortec heads and a baby LT4 cam and im unsure how tricky it will be to get the tpi to work with this and how to actually accomplish it.
or do i go with the vortec heads,vortec specific edlebrock rmp and holley(already have that too)as far as wiring and fuel system. i have a 1988 gta parts
car to pull everything off to go efi as well bujt im a little intimidated and have always been a carb guy.i need a push or some opinions/guidance

1986 trans am,slowly mating with several 1988 gta parts,vortec parts,umi parts and becoming a BEAST.its a long road.

do i use this L98?

OR THIS vortec L31 350,SUPER CLEAN!!!

 

Everything fit perfectly. If you believe that, i have some unspun rear tires for sale.

 

im even more terrified now,lol.

CARB IT IS...this car is an April to October vehicle(IF the Canadian weather cooperates)
and isn't raced,auto-crossed etc and due to the extreme distances to any road courses
i cant see it happening in the future either.the car is set up for carb,ive been running it
like that and enjoying it so im sure i will be happy with another 100-150 horsepower
increase and still use a carb.your car is bad a$$

 

Hi. I have a video on how to do it

 

I don't know, color me strange, my plan for my (ex) car- kids car is as I did with my buddies. Pick and pull 8.8 Ford, we cut everything off and welded it to the 8.8, I think he got it from an Explorer, I don't recall. Other than time invested, after bearings/etc...he was into it less than $400, and a very stout rearend. Now he ran steel wheels, so maybe some thought has to go into it for proper backspace for stock look, and then another 250/300 for axles, or less if you could get the ones redrilled.

Heck, thinking about it, why would anyone spend 3K+ on an aftermarket rear? All your'e doing is paying someone to weld stuff to it.

 

By all reports the 9 bolt is plenty strong enough for the majority of third gen's out there. Some of us already have them. I assure you it was nowhere near $3k to put the torsen and 3.70 gears in my 9 bolt. Close to $1k maybe. But that Exploder 8.8 doesn't have a Torsen in it so not really comparable. I would still take the factory fitment and the Torsen over some cobbled in 8.8 truck rear end and fiddling with Ford drum brakes, parking brake cables, and all the other nonsense and welding involved in such a mess. The 9 bolt is just cleaner. And besides this thread wasn't started to entertain comments about how some pick-n-pull Frod rear end is a better choice or even to discuss the merits of rear end swaps vs. stock rear ends in general...... It was started to provide information on swapping a Torsen into a 9 bolt Third Gen rear end. Nothing more. If you don't want to do that and prefer to use the Ford rear end - how about you start your own thread on that?

GD

 

I wouldn't call it a cobbled together rearend, take a good look at the "factory" welds on the 9-bolt. Nice, aren't they? It's all good, if you feel spending $ on the 9-bolt (I've had a few) is better than a local alternative, all fine by me.

 

Is this the correct torsen carrier that will fit our 9 bolt?
https://www.ebay.com/itm/273056734779

 

Clearly not. It most plainly says "Lada Niva" in the description. Which is Soviet, not Australian.



GD

 

If '22 teeth' correspondence to 22 spline, then of course no. The Australian one (Supa F) now a days are made in China, yes China. In any case regardless where it is made, if size is 7.75 and has 28 spline (provided correct diameter) and overall length is similar to original borg warner posi, then why not?

 

Where would be the best place to source this unit?

Looking to have my rear end rebuilt, and this sounds sublime.

Thanks!

 

The links for purchase are in the first post

GD

 

I checked the website and all the carriers are well over $500

Did the boost the price or do I need to email for a specialty purchase?

 

The strength of the USD changes against the AUD, so the price will fluctuate

 

$500 AUD is $343 USD.

Even at $500 USD it would be pretty much par for the course. Have you priced out a TrueTrac? A Detroit TrueTrac for a 10 bolt is $532 from JEGS.

I paid $530 USD shipped from Australia. That was in 2017. So I imagine the prices may have gone up due to US tariffs with China. It's been over 3 years since I did this install. Which BTW I daily drive my Trans Am, which now has about 400 crank HP and the VL Holden Torsen is working great still...... I'm about to do a brake kit from Big Brake Upgrade.com and put some C5 rear calipers w/parking brake on my 9 bolt.....

Compared to swapping the axle with something else like a 4th gen with a Zexel Torsen..... much cheaper if you already have the 9 bolt.

GD

 

Thanks for the thread GD. I am working on my 9 bolt currently, great info here. On you brakes, I too am looking at those, but I am looking at the C6. why are you going with the C5? What I read the C6 have advantages over the C5. Just curious.

*****

 

Fitment under my stock 16" wheels. I like my stock wheels and had them professionally restored and custom painted.

GD

 

I need to get one of these diffs soon!

 

Gotcha. I was looking to upgrade my wheels to the Hawk 17x9 and was going witht he C6. Good luck.

*****

 

 

Just bought the Mace locker,$612.00 total.(shipping,tax,) Waiting for the gear set to come in and about to order the install hardware when I finish this post.Thanks General Disorder and Key Key.You guys Rock!

 

I just bought my wheel bearings and rear wheels seals. Now I just need to by the rebuilt set from Strange Engineering.

 

Ra-Tech is who I got all my parts from. There are different sizes for pinion bearings and they have a better crush sleeve design available as well. I would consider the TA rear girdle cover to be essential for strength as well as fluid servicing also. The stock rubber plug for fill only is garbage. TA cover has drain, fill, and check plugs. Make sure to use thread sealant on the pre-load studs or they will leak. I used Loctite 545.

GD

 

awesome. Good tips. I bought a girdle. Similar to the TA Performance.

 

What make is that @Chevy86 IROC-Z? I can't imagine there is a big market for girdles for the 9 bolt

 

Looks like a bunch of vendors are rebranding the same cover. A quick Google search shows a surprising number of options for 9 bolt rear covers. Very strange.

​​​​​​GD

 

It looks EXACTLY like the TA Performance cover, but not as nice of a casting. It's probably a direct Chinese rip off of the TA cover

 

Oh yeah totally. It's likely an Ebay knock off. Doesn't have the USA cast into the bottom corner like the TA cover. And it's completely unbranded. I would be checking the tolerances closely as the Chinese knock off castings are often sized weird or have things shifted, threads loose, wrong alloy, etc. Wouldn't be worth the risk to me with the TA cover only being like $160.

GD

 

The dif cover was purchased from "overstock_diff" on ebay. When I bought the cover, the name on the paypal receipt is eBay - Brydon Papenberg (overstock_diff). A quick search of this person reveals a USA speed parts vendor who sells name brand parts. It would be terrible to know that https://www.quickperformance.com sells Chinese knock-offs. It would blemish his reputation.

 

Might be a quality control or cosmetic defect that the one I bought was cheaper. I'll keep you guys updated.

 

He is clearly selling used, damaged, open-box, and potentially sub-part components through this ebay store that he doesn't want on his name-brand web site. As a business you sometimes purchase parts for evaluation purposes and if they don't meet the high standards of your quality oriented web site - you off them on ebay. Not so hard to understand really. Has nothing to do with the website's reputation since he isn't selling it through the web site.

I see this kind of BS all the time. I had a car at the shop today for dyno tuning that was a complete pile of ebay and used CRAP. It didn't get tuned for a number of reasons - but it all boiled down to hack work and CHEAP parts. The whole car is straight garbage and I just had to smile and tell the customer "well that's how it goes sometimes!" and "better luck when you bring it back after you fix all that stuff!"

Don't be that guy.

GD

 

I'll date myself a little now, I am one of the people that got in on the original group purchase for the TA Performance 9 bolt girdle They wouldn't make them unless a certain amount of people bought them. I got it way back when and didn't install it until 2017

 

hahaha. Dang. Well I can assure you I'm not cheaping out. I have been collecting many brand name parts for my build. AFR 1040, CompCams XFI268, Delfi roller lifters, MSD6AL2 Ignition box, CompCams 1.6 Magnum RR, Eagle 383 kit, and currently get my block machined.