tifosiman

OK, Day One was the day I blew the trans last month and the SOW had an impromptu tech session in Dan's garage and we swapped another one in. I have since purchased that one and have decided to purchase the parts to rebuild the last one I detonated, in the hopes of swapping that into the car in the spring and having many worry free autocross events afterwards. I'm purchasing some hardened (Cryo'd and Rem'd) R&P gears from Powerhaus II since this is the 4th trans in the car and I am growing weary of the issue. My hope is that by posting the info as I go along I can show fellow rennlisters that a repair/rebuild at home is possible, and a better end product is the result.

So today, I skipped the Corvette/Porsche shootout and decided to start tearing the old one down to ensure that it is indeed rebuildable.

Here's what it looks like with the side access panel off (you need a 13mm socket and a 6mm allen wrench):



Yuck! I then fished as many chunks out as possible of the dead R&P gears. I used a magnet and my fingers and came up with this:



I then removed the back portion of the transmission that houses the gears and the pinion gear/shaft (you neeed the 13mm socket and extension, and something to pry the housings apart with, a pair of large flathead screwdrivers works great). From what I can tell, the gears look fine, no large bits made it back into that area thank goodness:



Here is a good shot of the pinion gear from directly on. Notice that there are NO teeth left on it. It's amazing that "143hp" did this, huh?:



This allowed for me to remove the differential and associated bits:



Everything other than the R&P gears looked fine, almost brand new. The next step is to completely clean everything, including the case/housing to ensure that there is no little metal chunks left. I used plastic baggies, a sharpie marker, and twist ties to remove, store, and mark all of the bolts and little bits so that I know where they go on re-assembly.

The next photo is interesting. My job involves accident and product failure investigations, so I was curious as to why this one blew up. I found the missing tooth for the ring gear, and it looks odd. Almost as if there was a hairline fracture on the outer edge long before the final kaboom. Usually in my line of work we would ship this off to a metalurgist for a formal investigation and report, but that isn't going to happen here on my shoestring racers budget. But, look at the shiny edge that extends about 2 milimeters into the tooth. It looks like there was an issue there that finally caused the failure, and then the gap in the ring gear created a dead spot that finally caught and detonated the pinion gear:



So, that's it for today. The next step is to thoroughly clean everything, and then verify what I need to order. My hope is that the new harder R&P from Powerhaus can hold up to whatever autocross can dish out. I'll post another update after I order and receive the parts, whenever the budget allows for it............

(anyone need to buy any old 85.5 N/A body parts to support my fund raising project? )

Jeremy

xsboost90

hm, interesting...youll have to let me help, and if it works out maybe ill have to do mine, and everyone else who will pay!!!

tifosiman

No problem, the more the merrier. I've been thinking about making it a SOW tech session (per Wade's suggestion). The hardest part about this equation is the cash needed for the hardened R&P gears.

I will definetly need your help swapping out the transmissions once I build the "uber-N/A-trans", it's much easier with more than one person, as you well know.......(those things are a bit unweildy)

Wade B

You know, it has me curious now; we may have to tear the one down that failed on me a few years ago just to see if it has the same type of initial wear pattern on the ring gear. We may be able to get more diagnostic info about the failures as I got to mine early enough that it still ran and all you heard was a "clunk" once every rev of the ring gear.

And I think since it looks relatively easy to jusy do the R&P I may go ahead and have this one as a spare.

tifosiman

That's a good thought. I'd like to see if this is the trend. I never tore the other ones apart like this one. Something tells me we will find it to be so.

Dale has Rock's old trans, we should pick a date and get together and tear both of those apart. If that is the same deal, then we have some good base info. And, we could then pick another date to do a group R&P replacement to outfit our spare transmissions. Dare I say, if we get enough people, maybe Roger at Powerhaus may give us a little break on the hardened R&P gear purchases.........

xsboost90

well, its simple, i dont know about easy. its def a test of patience and technique..and some tools too

Luis de Prat

Fourth transmission in the car?! How many clutches?!

86 951 Driver

Would a limited slip help save the ring and pinion on these cars? I never have heard of a car with an LSD breaking the ring and pinion. How can this be prevented?

Tom R.

AndyK was over at my house today, and we got my neighbor to start talking. I got him to tell Andy about the Karmann Ghia he had in the late 70s with a 2.2L displacement.

He said he had a deal with the local junkyard. Every month he would get another transmission for $100. Then one of the companies came out with a casing designed to handle the power.

He would appreciate the pictures you posted.

Then he told us about the 63 XKE coupe ho bought with 7k miles in the mid 70s for $500 from the owners widow.

KuHL 951

Those photos are absolutely scary. Not to cast stones here Tifo, but what is your driving style to do that kind of damage? What were the conditions or driving style right before the 4th failure. We all know the N/A trans is weak, but there are many here that see 200K miles before issues arise. Guess a Turbo trans upgrade is the obvious solution if you are looking for something with a stronger input for hard 1st gear starts even though the gearing isn't as favorable. Limited slip won't do squat if you drive too hard. I'm doing an 86 Turbo trans swap in the N/A soon now that my 'younger' driver has the N/A. Is it only me or do others here cool it a bit in first and second gear? I'm cheap, parts are expensive, especially trannies. Call me conservative or whatever but this trans failure pattern would get old very fast at my house.

nine-44

Hmm, might be just the excuse I need to buy that upright press I've wanted. I know my dad has various gear pulling tools and splitters. He has a smaller press that would do some of the work, but a larger press will be needed for some of the shafts.

Jeremy, you're up next anyway for the GTGs, I think we have a subject, Why trannys bust!

2Tight, I really don't think it's his driving style, he's probably easier on trannys than me and he doesn't go apesh*t on launches either.

Some of you know my personal theories on the case stressing under torque and letting the ring gear ride out to the edge of the pinion teeth. I'm starting to put some serious thought into making a rig to measure case flex...Hmm?

Another thing, the highest load on the R&P is in 1st and 2nd gear due to the gear reduction, Jeremy, along with quite a few of us do a fair ammount of AutoX, mainly 1st and 2nd gear.

One more thing too, I'm wondering if the turbo R&P is really much stronger, or if it's the turbo lag that save the R&P from the brutal power in 1st and 2nd? The NA comes on hard every time, Hmm?

Drag racing's #1 tip to keep your final drive in one peice, pull up all the slack in the driveline before launches, ie.. preload before launch.

Macfreak007

I am also very interested in this, but is this true that the LSD tranny's do not have to worry about this failure. If it is indeed still an area for problem on the early LSD tranny's I definately would be interested in learning how to rebuilt my tranny and put in the hardened gears, the peace of mind is all I am looking for. someone clear that up for me?

Sam Lin

Cool post Jeremy, good luck.

LSD is less likely to have this issue as there's less sudden shock loading when one wheel spins and then suddenly grips - that sudden grip is usually what blows the pinion gear if it's not from a blatant clutch dump.

Sam

nine-44

The shock to the gears is the fatal strike definately. AutoX has alot of on-off throttle, any lash in the gears is hammering them. Gears are hard, they will break before much flex, like glass, push damn near as hard as you want, no problems, you strike it mildly and it's shattered.

Macfreak007

So would I need to worry about this upgrade on the LSD or is it not something to worry about period? Is there even a r&p gear in an LSD? Sorry I know nothing aobut transmissions, as you can tell...