What power/torque is known to blow transfer boxes/rear diffs?

On a pretty decent powered project here so needing to know what kind of power/torque would blow a transfer box and rear diff?

Cheers

Rear diffs don't have a problem in general, driveshafts normally go first.
Standard box has been used on low 400hp builds without too much bother but all depends on what clutch you got & how you use it for standing starts.
Launching a low 300hp R with a 3 puk clutch or twin plate could soon kill the box while someone with a 6 puk sprung & less aggressive launch use could go on for years.
Also depends how good box is to start with & unless it very much low mileage it likely not as good as could be & any additional shaft end float or worn gear teeth can soon lead to failure once stress level increase.

Cheers for the reply. The box wont (shouldnt haha) be an issue, PPG, Stracher braced. Clutch is an OS Giken twin plate (rated to 600bhp, same as the box). Is it likely i'll have driveshaft issues then?

Probable as they 20+ years old & outer cv for example is nothing more fancy than what is on the n14gti but they cheap & quick to replace if you do pop one.
At end of day any transmission & drive component that taking launching, aggressive sprinting & hill climbing is likely have something break.
Driving style, perfection of transmission build, clutch type, wheel/tyre size & even luck all play a roll.

Generally driving style is a huge factor, treat it harshly and it's going to let you know pretty quickly. I'm using a PPG gearset aswell. At the end of the day the casings are still 20+ years old, so prior abuse is still an issue. The gearbox brace will assist in some ways, it certainly doesn't prevent all types of failures.

Wouldn't even worry about rear diffs or transfer boxes Colin as they are relatively cheap unless plated / lsd such as nismo or Modena

Stracher brace will help a bit but won't stop gear set poking it's head through bell housing end so need to have a bit of luck coupled with treating it nicely

There's one certain car I know about was running 574@fly and launched brutally but the relatively STOCK gearbox lives on and now in another big power car 
It's luck of the draw at the end of the day

As B said cv joints are a little weak but whoops doo, never seen an actual shaft shear though on one of these cars as pretty heavy duty stuff.

One thing that would worry me a little is running the is giken.........fantastic biting clutch, but in the past I've seen them strip  input shaft splines on 3 seperate  quaife boxes
But never seen them do It funnily enough on a stock input shaft : /

But at end of the day il be in same boat as you with regard to power and you have no choice other than fitting a high clamping pressure clutch assembly with torque figures around that Mark and beyond so choices are relatively limited

Stracher now do the bell housing gearbox brace, but its to be used with a Titon hydraulic release bearing,,, which i have no knowledge of. Ill need to go read up on it

So the OS Giken isn't really recommended then?

Oh Bob, did you see about those oil squirters?

ckd281081 wrote:Stracher now do the bell housing gearbox brace, but its to be used with a Titon hydraulic release bearing,,, which i have no knowledge of. Ill need to go read up on it

You can plate to to some extent & use standard release but for proper effort then indeed a hydraulic release bearing can create the extra space for a more robust solution.
Only problem I have had with hydraulic release (on evo) is quite rapid wear on the piston & fact they don't always have the best displacement to your master cylinder so pedal pressure & travel distance may not be best.
I ended up get one machined based on original but reworked displacement of the unit to increase pedal travel & thus required operating pressure & also changed material in hope of long service life.
Stratcher seems quite fussy on part selection & design so expect it quite good effort.

Yeah i have the outer brace and it looks spot on. Do you recon the inner brace added would make the casing bullet proof as claimed?

I would say it would be pretty close to it.
We had a very high 400hp drag gtir here that used a home brew end girdle & had a small plate welded bell housing end over snub of the bearing, that was on par straight cut gears after standard teeth failed & had single paddle clutch & ran most months at 1/4 mile events & seemed reliable & was treated quite rough.
Sounds like you running more power but you probably got better parts in the box & better case mods too.
so much comes down to driver & usage at end of the day, original case spec on whether early or revision spec & what it been subjected to over the years makes a difference, you can ultrasonic & xray casings & cryo treat worthy one.

ckd281081 wrote:Yeah i have the outer brace and it looks spot on. Do you recon the inner brace added would make the casing bullet proof as claimed?

have you welded the brace ?

No no the brace is still in the box. It comes with all the fixings included, so bolts to the box via the original casing holes

^ yes its a snug fit over housing & has some bolts but also can be welded to the casing for maximum strength if welding done well.

Hmmmm, I'll definitely be getting that done then. Is there an alternative for the bell housing other than getting the stracher? I was actually waiting months for the Stracher one to come but i never knew he was designing it with a hydraulic bearing,,, a specific one at that

alternative is welding a plate but it minimal due to space.
Any welding done needs be top effort with correct rods for case alloy & without warping the casing.
Have not seen the stratcher effort on bellhousing brace & release bearing so no comment on that yet.
Hydraulic release bearing is not bad idea if well implemented.

It's something ink ow nothing about though, the hydraulic release, hence why I'd probably prefer an alternative if there was one. I'll read up on it though, learn the ins and outs of it. Cheer

Whether it it is all needed very much depends on your intended use & power, your gearkit & shaft bearing type & how much budget you got or are willing to lay out
A lot of people have run some powerful R's with various home made end case support & nothing or a basic plate bell housing end & do ok on reliability.