Tuscan diff
Tuscan diff
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Discussion

garry-e2qnj

Original Poster:

22 posts

36 months

Does anyone know if a 2000 Tuscan btr diff is a Borg Warner m75 series?

Borg Warner, BTR , Dana M75 m76 m78.

Currently fitted with 3.73 gears and I can get my hands on a 2.77 gear set.

Currently my car at 70mph is revving at 3500rpm and I'd like to get it under 3000.

The 2.77 will bring it down to around 2660rpm at 70mph.

I know you'll all be saying that's not right which it isn't.

My car runs a BMW 5 speed diesel box as it can handle 1200 newton mtrs of torque.

Engine wise I'm running a 5.3 ls twin turbo v8 putting out 623.5hp and 570ftlb of torque at only 7 psi of boost.

First gear is pointless just like the motorway cruising speed hence wanting to change the gear ratio in the diff.

Been offered a 3.26 but that only brings the revs down to 3100rpm at 70 mph.


Any info on the diff is very much appreciated

Cheers

v8sag

792 posts

228 months

While the casing is m75/m76 the crown and pinion set is m78, that's what has confused a lot of people, so you'll want a m78 crown and pinion gear set.(8 bolt x 127mm bolt pcd, see pics for pinion sizes) I would only purchase genuine Dana/ Spicer or Holden gears, not aftermarket.

Not sure of the availability of the 2.77, the 3.08 is getting difficult to find, plenty of 3.23's. we've put the 3.08 in our ls builds here in NZ.

Aus is a great source for the BTR/BW diff parts if you're wanting to change lsd's too. Google M78 irs 28 spline output. Fitted to Holden commodore VL-VT1 and Ford Falcon XF to AU.

One thing to bear in mind with the 2.77, if you're wanting to change lsd's at some point in time, not all may work with this ratio, like the Harrop/Eaton tru trac for example.









Edited by v8sag on Saturday 11th October 01:30

garry-e2qnj

Original Poster:

22 posts

36 months

Saturday
quotequote all
Thanks for the info.

The gear set I can get is genuine Spicer gears.

Brand new old stock.

So which pinion shaft size would be fitted with the 3.73 gears that's currently fitted?

I'll email the guy to get some measurements from the Spicer gears.

garry-e2qnj

Original Poster:

22 posts

36 months

Saturday
quotequote all
This is the info I got about the 2.77 gears

BORG WARNER / BTR / DANA M76 & M76 & M78 2.77:1 RATIO GEAR SET / CROWN WHEEL & PINION GEAR SET

Have asked for more details but he's not got back to me yet

v8sag

792 posts

228 months

Saturday
quotequote all
Shaft diameters should all be the same. You definitely want the m78 set, I don't know why it would be advertised as m76-m78

garry-e2qnj

Original Poster:

22 posts

36 months

Saturday
quotequote all
v8sag said:
Shaft diameters should all be the same. You definitely want the m78 set, I don't know why it would be advertised as m76-m78
Have asked for more info.

Might see if I can find his phone number as it's a company selling it and give them a ring.

Will let you know how I get on

garry-e2qnj

Original Poster:

22 posts

36 months

Saturday
quotequote all
v8sag said:
Shaft diameters should all be the same. You definitely want the m78 set, I don't know why it would be advertised as m76-m78
Do you have any pics of the numbers that are stamped in to the crown wheel and pinion shaft?

Just so we have an idea of what we're looking for.

v8sag

792 posts

228 months

Saturday
quotequote all
Ill post some tomorrow as parts are at my workshop (upside down hours here!). There may be specific info relating to the 3.08 but that may help with cross referencing. If you do a pistonheads 3.08 btr diff search, someone did post photos of numbers in the Chimaera forum a few years ago.

garry-e2qnj

Original Poster:

22 posts

36 months

Saturday
quotequote all
v8sag said:
Ill post some tomorrow as parts are at my workshop (upside down hours here!). There may be specific info relating to the 3.08 but that may help with cross referencing. If you do a pistonheads 3.08 btr diff search, someone did post photos of numbers in the Chimaera forum a few years ago.
Thanks mate.

The 3.08 would work but again hard to find here.

Can get a 3.23 gear but still be a bit revvy at motorway speeds

Pagey430

160 posts

233 months

Saturday
quotequote all
Interesting thread. I fitted an M78 2.77 cp and needed a series 2 carrier to allow more space for the large pinion inside a BTR diff

Glen at 9bolt.com was a great help so I bought used examples from him, all good.

I too wanted lower motorway revs and this ratio helped me achieve 2500rpm at 80mph. Using a TKO600 1st isn't too tall in traffic either so I was happy with the overall gearing.

hope its of some help

John

garry-e2qnj

Original Poster:

22 posts

36 months

Saturday
quotequote all
Pagey430 said:
Interesting thread. I fitted an M78 2.77 cp and needed a series 2 carrier to allow more space for the large pinion inside a BTR diff

Glen at 9bolt.com was a great help so I bought used examples from him, all good.

I too wanted lower motorway revs and this ratio helped me achieve 2500rpm at 80mph. Using a TKO600 1st isn't too tall in traffic either so I was happy with the overall gearing.

hope its of some help

John
Did you get the 2.77 gears and series 2 carrier from 9bolt.com?

Pagey430

160 posts

233 months

Saturday
quotequote all
yep got both cp & carrier from 9Bolt, Glen knows his stuff so can advise if you need. I used a local specialist to build the diff up and they said no problem even if it needs spacers/shims.

regards

J

garry-e2qnj

Original Poster:

22 posts

36 months

Saturday
quotequote all
Pagey430 said:
yep got both cp & carrier from 9Bolt, Glen knows his stuff so can advise if you need. I used a local specialist to build the diff up and they said no problem even if it needs spacers/shims.

regards

J
Perfect mate thanks.

I have emailed him so hopefully he replies early next week.

Going to take the rear cover off mine next week to see what part numbers we can see.

garry-e2qnj

Original Poster:

22 posts

36 months

Saturday
quotequote all
Pagey430 said:
yep got both cp & carrier from 9Bolt, Glen knows his stuff so can advise if you need. I used a local specialist to build the diff up and they said no problem even if it needs spacers/shims.

regards

J
Just a quick one.

I take it the carrier is the section the ring gear bolts too.

I've never swapped gears over before so this is all new to me.

Mine is an LSD.

Mine is the same as this in the pics below




Pagey430

160 posts

233 months

Saturday
quotequote all
yep looks same casing as mine. That'll take upto M78. There is an M80 casing (Sagaris?) which looks the same but has a 6 bolt input flange, quite rare but stronger still with 8" gears instead of 7.75" (M78)

Yep carrier is what the crown bolts to, mines an LSD cone type (from 9 bolt)




garry-e2qnj

Original Poster:

22 posts

36 months

Saturday
quotequote all
Pagey430 said:
yep looks same casing as mine. That'll take upto M78. There is an M80 casing (Sagaris?) which looks the same but has a 6 bolt input flange, quite rare but stronger still with 8" gears instead of 7.75" (M78)

Yep carrier is what the crown bolts to, mines an LSD cone type (from 9 bolt)
So will the 2.77 gears bolt straight in?

This is all new to me. Not got a clue what I'm looking at and going 😂



garry-e2qnj

Original Poster:

22 posts

36 months

Saturday
quotequote all
Pagey430 said:
yep looks same casing as mine. That'll take upto M78. There is an M80 casing (Sagaris?) which looks the same but has a 6 bolt input flange, quite rare but stronger still with 8" gears instead of 7.75" (M78)

Yep carrier is what the crown bolts to, mines an LSD cone type (from 9 bolt)
Glen just replied to my email

He asked if it's an m78 or m80.

I don't know what that means.

Would you know what that means?

I take its probably to do with the internals of the differential

Pagey430

160 posts

233 months

Saturday
quotequote all
your current carrier will be series1, you'll need a series2 to go with a 2.77cp. Took me sometime to get my head around it but my delivery from Glen was 3 heavy items: Crown wheel, pinion and lsd carrier. I ended up selling the parts that came out which was a useful cost offset.
I had the opportunity to fit a Quaife helical carrier/diff which my transmission shop would machine to suit the cp, but more expense than I needed at the time.

personally I'd put this to a specialist to fit and set up, then all being well its a fit and forget

J

Pagey430

160 posts

233 months

Saturday
quotequote all
go M78, largest that'll fit

garry-e2qnj

Original Poster:

22 posts

36 months

Saturday
quotequote all
Pagey430 said:
your current carrier will be series1, you'll need a series2 to go with a 2.77cp. Took me sometime to get my head around it but my delivery from Glen was 3 heavy items: Crown wheel, pinion and lsd carrier. I ended up selling the parts that came out which was a useful cost offset.
I had the opportunity to fit a Quaife helical carrier/diff which my transmission shop would machine to suit the cp, but more expense than I needed at the time.

personally I'd put this to a specialist to fit and set up, then all being well its a fit and forget

J
Sounds like this is going to be expensive 😂

Is there any machining needed?

I know people who can fit it all and set it up.