Predator

I've been running the tranny from an '86 951 for about 18 months now with zero problems. I will admit that I've been baby-ing it as I had better things to do with my $$$$ than repair it. Lately, I've been wondering, just how strong are these units. I know BFR has about 10 conversions out now, all with this tranny, and as yet, not had a failure, and I know some of the owners, and they push their cars much harder than I do. So, anyone had a failure do to increase in HP/torque? Any data on these units, problems with non-maintenance related failures, or ways to improve the relaibility would be appreciated. Thanx.

ERAU-944

WHAT?

why bother with the conversion if you aren't gonna drive the **** out of it? you complain about n/a 'slowness' (which is really driver related rather than car), and then you don't push your porschev? shame on you! porsche built the 944 to have the **** driven out of it on a regular basis, did chevy not build the 350 for that? also, if you're worried about cost of replacement, i thought the 350 conversion was supposed to take care of high costs?

anyhow, i'd be interested to drive a conversion car (at least one that's properly done) just to see what exactly the difference is. i was always of the beleif that everything earlier than '87 had issues with the ring and pinion strength, because germany was having a hard time getting quality metals... so if that really is true then i suppose you should continue to baby it. if not, thrash away!

-Mike-

adie

And now for a more educated answer, I think a lot of the problems are related to the weight they are dragging around, I used a very late Turbo LSD box but I didn't like the gearing, i snapped 3 half shafts clean shear with this box. No wear on the gears when I rebult it with the 3.88:1 gears. The new gear set has me slightly worried as it will take more of a shock but it has me deep in the 10's and is holding up well, however here's the real hit, my car weighs in at 2090lbs give or take a bit. My Auto ended up looding it's fluid and burnt out, the second box (from a breakers yard) is now taking 1-2 miles before it will change out of first, I have another box but it's a late one so the cooler lines are different. While it is suposedly true the earlier (non turbo box's are weaker) it may just be that there seeing higher loads because of the different gearing, also these box's do seem to give up at the top end sugesting that with high sustained RPM there pushing the cases apart causing the failure. Most guys in the cup challange (UK) have had the odd one or two go but nothing compaired to say the T5 or LT77 box's. I think the weakness lies in the P.O. and there ability to change the oil and have the right oil as well, I'm in no doubt that the LSD on the later cars also preserve's the box to some extent and it doesn't allow the box to spin um when one wheel looses traction, another thing to note is tyres, most of the people I mix with use racing tyres, if they break loose thay break loose, if they grip they grip, a road tyre with almost judder as it starts to break loose, where it grip slip grip slip's thus exposing loads many many more times than a car with less power that doesn't quite let the tyres break away as much. If my box goes I think it will go on the line, and so for it has been excellent, I will admit the milage or that one is about 500 miles a year and the auto seems to be on it's last legs, but that does nearer 10,000 miles a year and 5,000 of those are towing the race car so its allowed to puff and pant a bit. Unfortunatly with your type of conversion you are exposing the box to loads it wasn't really designed to do, however i think theres more strength in them than they are given credit for. Now I'm sure loads of people are going to say that there 3.38 LSD ext, cooled box just died on them as they were pulling out of the driveway but somehow I think the higher geared, harder thrashed box's tell a bigger story. Just my findings on pulling a few box's down and doing some DP angle measuring.

Rich Sandor

2090lbs??? what is that a carbon fibre chassis?

adie

Not exactly, lets just say if it crashes it will look like a F1 car nothing left but a cage and me inside, .............. hopefully. no need for any fancy stuff so I removed it, even spare wires, got to the point of drilling the centre of nonessential bolts, cutting any overhanging threads off, no floor in the rear and just a little fuel cell, the doors are just f/glass skin on an alu frame, window stuck in the channel of the frame and a door latch, 1 jazz seat on alu section floor, f/glass rear hatch with small lexan window. Oh and of course the lighter engine, If it wasn't needed it was removed, also remember it started off life as a '924' f/glass fenders, no lights, you get the picture, +22lbs for the bottle.

Legoland951

It probably does reduce the maintainance costs but the weak link transmission is still Porsche. I think removing it and sticking a richmond transmission would make the conversion complete along with a vette diff.

Rich Sandor

Ahhh your name isn't Colin Chapman by any chance is it??? A man after my own heart.. LOL.. One of these days I'm going to get a 951 tub and give it the similar treatment..

dave120

From what I've always seen it's the CVs that are going to have problems long before the tranny does. If you get some more solid axles you might start to notice the tranny having problems. There's plenty of people on here with 400+ horsepower and stock 951 trannies. From what I see they're fairly durable.

Predator

Thanks for the replys. I know the CV joints are a weak link. I've spoken with a company that manufacturers high performance cv joints and they have ones to fit this car. I wish I could remember the name of the company. After speaking with the guy a couple of times, he confided that their products were really not that much stronger that stock units. They did have a nice gold anodized look to them, but I think they were over $400 per axle, so I passed. Has anyone ever done business with Powerhaus? I think they make different gear ratios, along with ring & pinion sets for this tranny. Wonder if it'd be worth the cost ?

Epic2112

I've bought stuff from Powerhaus. I won't go into details, I'll just say their service was stellar at least. I'm very happy with them.

tifosiman

I think that's "Powerhaus II" that sells those, not "Powerhaus", they are two different companies I think.

adie

I had mime done at prodrive in the UK, the machining required to cut gears is astronimical, I paid aound £300-500 but it was so long ago I honestly don't remember. I'd try Quaiffe direct as it doesn't look to different from one of there units.

adie

this was my problem, snapped em like carrots

Danno

How the #($*%&!@ did that happen? The ultimate strength for mild-steel is something like 80,000psi+. Over 110,000psi+ for chromoly. I can't begin to imagine the forces that was required... Could be notch failure from a scratch... corrosion... hmmmm... Were you running drag-slicks @ 15psi???

Rich Sandor

You can't say that objectively because I would imagine that different thicknesses of different types of metal would give you different torsion limits. Not to mention some twist and bend whereas others will straightup break.

However, I remember hearing that the MOTEC 968 once sheared the CV joints right off at the bolts.. on street tyres. Now that car apparently has an Audi Racing gearbox in it.