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FAQ BoardThis board is where some of the most informative and helpful Frequently Asked Questions we get here at ThirdGen.Org are put for easier reference. This IS NOT a general question board.
9 Bolts came on 86-89 FBodies. You can get all parts and more info from 9bolt.com.
This sounds correct but not all cars got them. I know some IROC's did and probably a lot of others. But V6 & V8 Camaros did not automatically get them and some Z28's did not. Not sure about the Firebirds.
FYI- I looked into the 8.8 and a lot of other swaps for rears and ended up going with a Moser 9" housing and a Quick performance third member. It has taken a beating for the past year and a half at the track and is still quiet and reliable on the street. I did not notice any loss of efficiency as generally associated with the 9" gear set.
I spent about $700 rebuilding and upgrading my 9 bolt. My 86 TA has one which I am running right now and a 89 firebird formula I had also had a 9 bolt w/pbr rear brakes that I look before I got rid of that one. Not all of them had them it was an upgrade or if you kept on blowing up the 10 bolt under warranty. I couldn’t swing the $3500 for 9” right now.
I hear you and that is about what I spent all in for the 9",
However, if I were running an auto I would have stayed with the 9 bolt. It is a great rear end and even has some advantages over a stock 9". I was looking to upgrade axels and some other internal improvement which would have run the cost up closer to $2k so it wasn't as big of a step for me. The 9" has so much aftermarket support and I figured the money was well spent since I run it at the strip a lot on slicks and a stick shift.
ok im reading things and confused. Does the eaton true track conversion for the 04-06 gto work in our rear ends? I have a 9 bolt with a 3.45 gear set and the cone is worn into the carrier and jammed up. Looking at the 9bolt.com tru-trac posi. and it looks similar to the Detroit trutrac.
The offset is different on the a GTOs . It’s in another post. You can get the diff at a better price right from one of the supplies Supa F Spares from Australia. I just paid with shipping to Chicago right under $500 for the truetrac.
The Borg Warner 9 Bolt Rearend is actually called the M78 Rearend or "78 series". It has been made since the late 60's in Australia by a company called BTR Engineering Ltd. BTR was bought out by Borg-Warner under which company name the rears were produced for our cars. In the last few years Borg-Warner was bought out by Dana Corp. and the rears are still produced by Dana today in the same BTR factory under the "Spicer Axles Australia" name. www.spiceraxle.com.au/products.htm#srd
The rear is offically rated @ 220 kW = 295 HP
@ 435 Nm = 320 lb/ft
It can support a GVW of 2740 kg = 6041 lbs
The above ratings seem to be a bit conservative, as one member I know of has one that has survived the abuse of a 500hp/500+ lb/ft Big Block for a few years now. The 9 bolt offers a few advantages over a 7.625" 10 Bolt: 4 pinion spider gear design, shorter distance between carrier bearing caps, and a 7.75" ring gear diameter adds strength.
All 9 bolt rears for f-bodies use 28 spline axles.
Another advantage over the 10 bolt is it uses pressed on tapered axle bearings allowing the axles to be bolted in instead of using c-clips. I've heard several people say the 9bolt is stronger than the Dana 44. I do not believe this because in my many years of research, I've never seen one shred of FACT to support it. The dana 44 uses bolt in axles and has a larger 8.5" dia. ring gear versus the 9 bolts 7.75" dia. ring gear. Most, if not all Posi Dana 44's built for camaro's were 4 pinion versions also. Dana 44's were used by GM as service/warranty replacements for problematic 9 and 10 bolt rears, then offered them thru GM Performance Parts, and they were then used on the 91-92 firehawks if that tells you anything.
85-90 9 bolt equipped f-bodies were available with either standard open differentials or limited slip versions as well as several different ratios including: 2.77, 3.08, 3.27 (G92 w/auto), 3.45 (G92 w/stick), and a few 3.70 ratio's came in some 85 & 86 Firebird's w/ RPO Option Codes L69 (305 "High Output" Carb Engine), 5 speed trans, & G92 =Very Rare!
3.27 and numerically higher gears will not fit on 3.08 and numerically down carriers. If you have a 2.77 or 3.08 rear and want 3.27 or higher you will have to get a 3 series carrier. www.9bolt.com.
The "Limited Slip" or "posi" rears used on f-bodies used what is called the "Seperated Cone Slip Resistant Differential".
They also make a better version called the Hydratrak SRD but it uses a different spline count on the axles preventing it from being a direct swap into our rears
Vehicles originally equipped with the 9 bolt rear:
Australian made cars: Certain models of Ford Falcons since 1971, Holden Commodores from 1986 thru 1991, Chrysler Valiants since 1971, certain Aussie made Toyota Corrollas & Coronas, Nissan R31 Skylines/Pintaras & certian Datsun's, Mitsubishi Sigmas, Leyland P76s ...1997-up Morgan Plus 8s have the Hydratrak version. In the UK the rears were used on certain Vauxhall models and Jensen-Healey's.
I've also heard that Ford uses the 9 bolt center section in their Escapes and Mazda Tributes, but I haven't verified it yet.
The Nissan Austraila PN for 3.9 gears is 38100-J7100
3.7 gears were used in R31 Skylines with manual trans, the PN for those gears is 38100-J7110
4.1 gears were used in R31 Pintara's (manual or auto) and the PN is 38100-J7000
Holden's and Fords got nothing shorter than 3.45 gears AFAIK.
In 1998 the Australian magazine "Street Machine" did a series of articles on this rear axle, Another member has posted it somewhere in the thread below.
where would I get the 7.75 ring and pinion? I didnt know there was such a size? I thought it was just 7.62 ring and pinion? I was also looking into a 8.2 Ring and pinion with the 28 Spline Axels and see if it would fit the 7.62 Rearend? Thank you for your time on this matter.
You can only get 3.70 gear ratio in the 9 bolt B&W rear end in the aftermarket. All the normal companies make them. You can get good used OEM quality ratios from 9bolt.com. I have a 9 bolt with a torsen style diff w/3.70 and I am having no issues. Works much better the OEM cone type.
The M78 is 7.75" and the related M76 is a 7.5". The 7.5" will fit into the M76 housing with the correct pinion spacer. I think I have an old post with the info.
I had 4.11 7.5" gears in my M78 that I bought used in New Zealand on vacation and ran them with a built LT1 with drag radials with no issues. You can get them there used for about $100.
The Borg Warner 9 Bolt Rearend is actually called the M78 Rearend or "78 series". It has been made since the late 60's in Australia by a company called BTR Engineering Ltd. BTR was bought out by Borg-Warner under which company name the rears were produced for our cars. In the last few years Borg-Warner was bought out by Dana Corp. and the rears are still produced by Dana today in the same BTR factory under the "Spicer Axles Australia" name. www.spiceraxle.com.au/products.htm#srd
The rear is offically rated @ 220 kW = 295 HP
@ 435 Nm = 320 lb/ft
It can support a GVW of 2740 kg = 6041 lbs
The above ratings seem to be a bit conservative, as one member I know of has one that has survived the abuse of a 500hp/500+ lb/ft Big Block for a few years now. The 9 bolt offers a few advantages over a 7.625" 10 Bolt: 4 pinion spider gear design, shorter distance between carrier bearing caps, and a 7.75" ring gear diameter adds strength.
All 9 bolt rears for f-bodies use 28 spline axles.
Another advantage over the 10 bolt is it uses pressed on tapered axle bearings allowing the axles to be bolted in instead of using c-clips. I've heard several people say the 9bolt is stronger than the Dana 44. I do not believe this because in my many years of research, I've never seen one shred of FACT to support it. The dana 44 uses bolt in axles and has a larger 8.5" dia. ring gear versus the 9 bolts 7.75" dia. ring gear. Most, if not all Posi Dana 44's built for camaro's were 4 pinion versions also. Dana 44's were used by GM as service/warranty replacements for problematic 9 and 10 bolt rears, then offered them thru GM Performance Parts, and they were then used on the 91-92 firehawks if that tells you anything.
85-90 9 bolt equipped f-bodies were available with either standard open differentials or limited slip versions as well as several different ratios including: 2.77, 3.08, 3.27 (G92 w/auto), 3.45 (G92 w/stick), and a few 3.70 ratio's came in some 85 & 86 Firebird's w/ RPO Option Codes L69 (305 "High Output" Carb Engine), 5 speed trans, & G92 =Very Rare!
3.27 and numerically higher gears will not fit on 3.08 and numerically down carriers. If you have a 2.77 or 3.08 rear and want 3.27 or higher you will have to get a 3 series carrier. www.9bolt.com.
The "Limited Slip" or "posi" rears used on f-bodies used what is called the "Seperated Cone Slip Resistant Differential".
They also make a better version called the Hydratrak SRD but it uses a different spline count on the axles preventing it from being a direct swap into our rears
Vehicles originally equipped with the 9 bolt rear:
Australian made cars: Certain models of Ford Falcons since 1971, Holden Commodores from 1986 thru 1991, Chrysler Valiants since 1971, certain Aussie made Toyota Corrollas & Coronas, Nissan R31 Skylines/Pintaras & certian Datsun's, Mitsubishi Sigmas, Leyland P76s ...1997-up Morgan Plus 8s have the Hydratrak version. In the UK the rears were used on certain Vauxhall models and Jensen-Healey's.
I've also heard that Ford uses the 9 bolt center section in their Escapes and Mazda Tributes, but I haven't verified it yet.
The Nissan Austraila PN for 3.9 gears is 38100-J7100
3.7 gears were used in R31 Skylines with manual trans, the PN for those gears is 38100-J7110
4.1 gears were used in R31 Pintara's (manual or auto) and the PN is 38100-J7000
Holden's and Fords got nothing shorter than 3.45 gears AFAIK.
In 1998 the Australian magazine "Street Machine" did a series of articles on this rear axle, Another member has posted it somewhere in the thread below.
Question: Are the 2nd and 3rd series center sections the same. I have a nice 2nd series center section and wanted to use it in my 3rd series carrier.
I mean the complete center section housing, cones, spiders etc.
The CARRIER, is either a 2 series or 3 series. it IS the "center section". The only parts that are the same between the two are the spiders (and associated parts) and the cones. You need 2 series gears for a 2 series carrier and you need 3 series gears for a 3 series carrier.
If there were thick gears available you could get thick gears for your 2 series carrier to run the numerically higher gears.
I actually really like my 9 bolts I have one from an 85 trans am, the Camaro and firebird production years are different I believe the Camaro didn't get it tell 86 while the trans am got it mid year 85 I found one I a wrecked Firehawk 93 don't know if it was factory or custom built by SLP or just custom built. The oversized cones work really well if you know what you're doing you have to grind down the inside of the differential housing. 3.70 aftermarket gears are noisy as hell if you don't want the whine buy a set of factory 3.70's they're a lot less noisy or a set of 3.90's if you're running a T-56 like I am I chose the 3.70's and I hate the noise. I'm also gonna do the big brake kit LS1 rear brakes on my 9-bolt I'll post photos when I get it. I've rebuilt 14 of these so far usually the lifespan is 70 thousand miles if set up correctly with new cones. If you need help with anything let me know I'll message back when I can.
ok im reading things and confused. Does the eaton true track conversion for the 04-06 gto work in our rear ends? I have a 9 bolt with a 3.45 gear set and the cone is worn into the carrier and jammed up. Looking at the 9bolt.com tru-trac posi. and it looks similar to the Detroit trutrac.
Originally Posted by howie099
The offset is different on the a GTOs . It’s in another post. You can get the diff at a better price right from one of the supplies Supa F Spares from Australia. I just paid with shipping to Chicago right under $500 for the truetrac.
I actually really like my 9 bolts I have one from an 85 trans am, the Camaro and firebird production years are different I believe the Camaro didn't get it tell 86 while the trans am got it mid year 85 I found one I a wrecked Firehawk 93 don't know if it was factory or custom built by SLP or just custom built. The oversized cones work really well if you know what you're doing you have to grind down the inside of the differential housing. 3.70 aftermarket gears are noisy as hell if you don't want the whine buy a set of factory 3.70's they're a lot less noisy or a set of 3.90's if you're running a T-56 like I am I chose the 3.70's and I hate the noise. I'm also gonna do the big brake kit LS1 rear brakes on my 9-bolt I'll post photos when I get it. I've rebuilt 14 of these so far usually the lifespan is 70 thousand miles if set up correctly with new cones. If you need help with anything let me know I'll message back when I can.
85-89 is when the 9bolt was offered in the f-body.
A 93 firehawk uses a 10bolt and 93-02 rearends are wider than 3rdgens, 1.5 to 2" wider a side.
For those who don't know the difference in the 9 bolt wheels seals, there is a small difference between left and right. Not sure if it makes a difference, but here is the part numbers and differences. Notice the small lines inside the rubber seals and how they differ in direction.
USA GM had a contract with BTR from 82-92 covering drum and disk brake axles
as the axle was used in special eddition cars the years where you find them will be years when they did a run of TA or IROC
so your camaro or firebirds made during that time COULD have a 9 bolt.
and it could be POSI or open centre
i have a friend with a 91/92 firebird that has a 9 bolt
If the previous owners broke the 9 bolt during warranty, I belive a dana was supplied...i'm guessing a 44 or something like that, I might be wrong
GM in Australia used these axles and derivatives in many sizes until they closed the factory down about 10 years ago.
dave
Here in CANADA new parts for 9 bolt Borg Warner are very hard to find. for example no more new GM or stock axle, back plate for disc brake and the list go on.
The bearing and seal are still available.
Mine is a 9 bolt from 1988 Iroc-Z G92 the driver side axle is leaking inside the mag wheel my mechanic change the bearing and seal 2 time and is stil leaking, after axle vérification
we can see some little pitting in metal where the bearing is press-in. it is very small but we think the problem is right there.
Anyone ever have this problem?
I'm sorry for my english, i hope you understand my nessage well..
Here in CANADA new parts for 9 bolt Borg Warner are very hard to find. for example no more new GM or stock axle, back plate for disc brake and the list go on.
The bearing and seal are still available.
Mine is a 9 bolt from 1988 Iroc-Z G92 the driver side axle is leaking inside the mag wheel my mechanic change the bearing and seal 2 time and is stil leaking, after axle vérification
we can see some little pitting in metal where the bearing is press-in. it is very small but we think the problem is right there.
Anyone ever have this problem?
I'm sorry for my english, i hope you understand my nessage well..
Thank you.
parts availability for the 9-bolt BW rear end is same here in US. So it's not a Canada thing.
I had the same problem with pitting of the axle under the seal. I was able to source a few used axle sets off of ebay a while ago, shipping was horrendous, but you got no choice. however, I was able to fix (probably temporarily) the pitted axle by polishing the pitted area with very fine sandpaper, e.g. 600 grit and higher. I polished the living daylights out of that area, replaced the seal, and it hasn't leaked yet. I think that was 20k miles ago, seems to be holding up. if it starts to leak again, then i'll have to replace the axle with another used axle. It's certainly not a good situation.
They have zero quality control, they shipped to me 4.10 gears and they had a damaged ring gear and I repaired it per there recommendations.
Then I installed everything just to have a clicking sound that I thought was bearings and I replaced the already new bearings again and then I set up the gears again and wouldn’t you know the light clicking turned in almost a dead stop at the same spot.
Backlash was set to 0.008” and the dead spot was zero.
Garbage just garbage.
And they won’t even respond to emails ever, when you have a question about instruction errors they leave you to really just figure it out on your own.
Finally if you want an exchange, replacement bearings for your gears in the event that there gear sets are garbage or are refund “for get it”.
They also don’t put an installed pinion height number on the pinion either.
Don’t be fooled by these Aussies!
Last edited by Tombowman89; 02-22-2023 at 07:14 PM.
09-18-2018, 08:22 AM
