VirginiaF1

Sorry for your issue mate..
As a precaution on high mileage 944's is there a benefit in going to neutral or clutch-in during corner transitions involving rough/broken pavement?
The thought is to minimize jarring the transaxle as much as possible ...
best wishes

JustinL

Just back off the throttle if you anticipate wheel hop. I'm a firm believer that it's the impact that breaks stuff in the drive line. I've launched my car with R-compound tires repeatedly for years and never broken a CV joint. Slip the clutch for an instant to get everything smoothly loaded before dumping the rest of the clutch.

I have broken 2 cv joints in my younger years. Once during a snappy clutch dump with no slip, and the other accelerating hard over bumps. Both of those were on street tires.

Van

"Clutching-in" puts excessive wear on the throw-out bearing... which is time consuming to change on a 944.

bordin34

Ok, so I drained the trans today and found a lot of chunks of metal. So I'm fairly confident I killed the ring and pinion.

bordin34

Pictures of the bottom of the drain pan

Van

Ouch! Sorry to hear.

bordin34

I killed it good

fortysixandtwo

If its worth doing, its worth doing right. You completely stripped that pinion!
It makes me wonder if there was some prior damage, and it finally wore enough to let go.

Edit: Just saw you drove a half mile after the ice cubes in a blender sound started. Yeah, that would make a ring and pinion smoothie.

bordin34

Yeah the driving probably didnt help.
Also it is a worthwhile upgrade to buy an S2 transmission instead of using the one from my 1985.5 parts car.

KevinGross

Check two things on your current gearbox: see whether you can turn the left hand side differential carrier bearing outer race by hand, ie, whether it has lost interference fit with the case. Separate the gear carrier from the differential carrier and do the same test to the front pinion shaft bearing outer race. If either turn, the case is junk and the transmission not worth rebuilding. I find that one or both of these races get spun perhaps 50 - 70% of the time when the pinion breaks. Otherwise, your current box can be rescued.

The S2 transmission is geared too tall for an eight-valve normally aspirated 944. Not a choice I'd recommend.

Kevin
Catellus Engineering

bordin34

Thanks.
So what about the S2 and turbo ring and pinion makes it stronger. Is it a larger size?

JohnKoaWood

For 5x the cost of a replacement gearbox (granted the replacement is an unknown....).

I would recommend the o use the box out of his parts car, and not beat up on it!

KevinGross

Yes, rebuilding the transmission is more expensive than throwing a "good" used gearbox in the car. Depends on whether you are committed long term to the car, planning to track / race it, budget, don't mind riding in the flatbed cab on the way home, etc. To quote Stan Hanks, "You already own a used gearbox." Can't tell you how many "good used" gearboxes I've looked at that are rubbish. If you go that route, get it from someone who can be trusted: I trust George B at 944 Ecology.

I have a 968 gearbox in the shop right now that was to have had a LSD installed, was told it has 40k miles on it. Problem is, it's missing a dime-sized chunk out of one of the diff carrier bearings: way too many years and miles on it. Further tear-down just uncovered more worn out parts.

The S2 and Turbo pinion gear is stronger largely because it has teeth that are wider at their root. Gear teeth load up essentially as a lever arm: classic mechanics. Peak load is at the tooth root, width there determines strength of the part, and that's where you see the breaks. You can make the normally-aspirated eight-valve 016 gearbox last by doing two things:

- Change the fluid, keep it clean. Plan to do it annually, feel good if you actually get it done every other year. The lubricant quality has a huge effect on longevity of the pinion because of its offset (Klingenberg) design.
- When you get it serviced, get the work done by someone who takes the time to measure and set *everything* up properly, using the factory tools, following the factory procedure.

I have a lot of racer and DE clients running these gearboxes, or ones with the smaller 4.11 r&p, and they don't break because they're maintained properly. I do a dye-penetrant test on the smaller pinions when rebuilding, which has saved some customers grief.

Kevin
Catellus Engineering

KevinGross

PS: in the second photo on the "I killed it good" message, I see a ring of dimples punched in the diff cover around the carrier bearing outer race. I am guessing that someone went into this gearbox, there was no interference on that bearing's outer race, and they punched "upset" marks in the cover plate to try to hold the bearing race. This was not a good idea and I have to wonder what else happened. It did not come from the factory this way.

Kevin
Catellus Engineering

bordin34

Thanks, I was wondering why those dimples were there.
What I am going to do is swap in my unknown parts car gearbox after just visually inspecting the r&p to make sure it isn't bad too. If that is bad I will try to get a used "good" one since right now I cant afford to buy a rebuilt one.
Edit: Also I will be running MT-90 fluid.