Borg Warner upgrades

[Hot Rod]

I have signed up with this forum because I believe there are experts out there who can give me advice please ( 1st post )
I have had Commodores in the past , but not currently owning. I am building a hot rot and decided to use a BW rear out of the earlier Commodores, this one from a VN. It's only an open centre 3.08, but after two engine change of mind I now agonize that it will not be strong enough.
First question is --- how much stronger is an LSD over the standard diff centre ? I know how an LSD works, but if I'm not spinning wheels or doing burnout / dragging does the LSD still provide some extra strength ?

Secondly, if the centre does go bang, what would be the most street friendly replacement centre ----
KAAZ
Detroit True Trac

I should mention the engine will be approx 320HP ( 240KW )
What are your suggestions please.

 

[TI3VOM]

The standard LSD is the biggest piece of **** out there.
Please do not spend money on it.


Not sure what model the VN diff is, but you will be referring to the Eaton True-Trac. I have a feeling it won't fit.
The Harrop option might fit (not sure on this 100%) but it is around $1200-1500 for the center alone!!

Power handling of the two:

Eaton True-Trac around 500 RWHP

Harrop True-Trac around 500 RWKW

My suggestion will be to call a few diff shops and ask what they would suggest, they will have a better idea as they fit the bloody things every day.

But again, please do not spend money on getting the stock LSD rebuilt. They will fail even if you don't do burnouts, all you need to do is drive the car hard from side to side and that wears them out prematurely -bloody pathetic.

 

[_R_J_K_]

+1 don't waste time with the cup and cone.

 

[Hot Rod]

So what you are saying is that there is little benefit fitting an LSD over the stock open centre ? ( for strength / wear )
Or are they both just crappy ?

 

[stuntmanmike]

Welcome & cool to hear that you're building up a 'rod. The stock BW78 (aka BTR78) live axle diff from the VL-VS is good for 400hp (or a tad more if looked after).
The LSD units can become unreliable. A 20s or 30s style rod are typically light at the business end. If you will have a tendency to mash the right foot (it can happen) then perhaps an open wheel centre is what you're looking for a base unit to build up by opening the ring gear case and replace the 4 pinion open wheel centre with a "Lokka". The Lokka operates with spring loaded hats that engage/ratchet the pinion centre under acceleration; can be noisy though and playing with the springs requires some thought for tuning the locking operation. It's hard to beat the TrueTrac unit for price and performance and this option will require a LSD diff housing instead. Some info here: BW78 LSD or lokka? which one? - Driveline - GMH-Torana
I'll assume that you have not opted for the venerable 9" due to the weight and costs relative to your drivetrain power output. The BW78s are also available in the Fords (sorry forum members for using that word). Various diff ratios are plentiful. 4.11s can be found in Nissan Pintaras and 3.89s/3.91s from auto R31 Skylines. 2.77s can be found in Fords if you are after the low revving type of ride for interstate rod runs etc. It all depends on your engine cam range and the gearbox ratios behind it and how you like to drive the beast. A Centura diff housing with BW78 internals is a popular mod for a rod due to the narrow track. Centura diffs are a bit light on at wreckers for this reason alone. VC Valiants are the next track width up from the narrow Centura if I recall correctly. Saying that, have a think about what track length you need and the diff yoke position/offset required for your rear end setup.
Have a look at http://www.#################/drivel...asics-salisbury-borgwarner-bw78-ford-9-a.html
Others may chime in with other tips and info that will assist with your design basis.
Best of luck with the build...

 

[WazzaVN]

Hey mate don't listen to all the nay Sayers on the stock lsd. Yes they are piss weak if you abuse them (IE throwing loops) but if you are pretty sensible they will last you a long time. I have a bw 78 lsd that is still going strong after 5 years and it doesn't get treated well at times. It all depends on who is setting it up. If someone sets it up wrong it will be lucky to last 5 km but if set up well it will last a long time if used with a little tact. The 78 Centre is allot better than the M80 Centre.

As for general strength of your diff the gears them self are most definitely up to the task of the HP numbers you are after. You would have to be very unlucky for them to break unless they were set up really bad. Before the gears the axles will be the first thing to go, but I would say you should still be safe with them too.

Of course aftermarket centres are 100% more reliable but if you really just want to take it easy I see no problem with buying a nice reco oem lsd and not waste thousands on an aftermarket unit for no reason.

 

[Hot Rod]

Fellas, thanks heaps so far for your comments. I did not consider the 9 inch because of cost. I chose the BW diff because they are cheap to buy and could adapt the whole suspension set up to my chassis. I believe it will ride much nicer than leaf springs on a 9 inch. I got a VN diff housing cheap and shortened it and will be using 2 short axles.
I am not a young rev head and will not be undertaking any form of burnouts. Just wanting piece of mind that the diff will be up to the task of everyday street driving with the 401 cu in Buick Nailhead motor ( heaps of torque ) the occasional squirt up the road but definately not wanting to spin tyres ( Police here have Hoon laws that confiscate your car anyway )
My rod build is a pick up so may be a bit light on the rear end weight wise. Just saw on Ebay a centre available from Torqueline Differential in Victoria for $595.
Seem to be similar to a True Trac but 1/2 the price. Anyone know of these ? Made in China ?

 

[Immortality]

A properly built BW78 with factory style LSD is good enough to survive a 9 second pass in a turbo VL V8 it should be strong enough to survive what you're intending to do with it. I know of a few 10 sec cars with the same BW diffs too.

An LSD centre isn't any stronger as such than a standard open centre. They both use the same 4 spider configuration the only difference been the LSD function. As mentioned above, if they are built properly and the aim isn't to cut hoops all the time than they are more than fine.

I've just had a look at that diff you mentioned, possibly looks like a copy of the Eaton/Harrop true-trak. For that sort of money why not try it.

 

[Hot Rod]

" An LSD centre isn't any stronger as such than a standard open centre. They both use the same 4 spider configuration the only difference been the LSD function. As mentioned above, if they are built properly and the aim isn't to cut hoops all the time than they are more than fine "

I've just had a look at that diff you mentioned, possibly looks like a copy of the Eaton/Harrop true-trak. For that sort of money why not try it


Thankyou Immortality, that's what I was hoping someone would say. Maybe I worry too much, probably best I finish the car and then try it out. And yes, that Torqueline centre does seem to be worth a try at that price.

 

[Immortality]

The other question that should be asked is what type of transmission you intend to run?

Auto's are a lot more forgiving on the driveline.