930 failure?

[BruceA]

That r/p set for the G50/0x is the same size as my UN1-13. I just ran down to the workshop to measure it!
Yes, I thought too that the 930 had a different diff unit.
I adapted a 4-spider unit from a 369 box to my UN1 crownwheel for the very reason of strength.
Yep, torque is the killer and I hope my new 406 V8 doesnt turn my gearbox into a twisted peice of metal.

 

[Pete T]

The pict's are a little deceiving. The two diff's are the same. The ring gears ade different. The G31/915/930 all use the same different diff. The ones in the pict's are open. I have a ZF lsd in my G31.

For those that don't know what a G31 is, it is a transaxle that was used in 1979-80 924's. It is based on the 915. The diff and gears are the same, the mainshaft and pinion bearings and retainer is the same, 3-5 gears are the same. The synchros for 1 & 2 are based on the 930, probably due to the long torque tube etween the engine and transaxle.

One thing to note is that the mainshaft, pinion bearings and bearing retainer between the 930/915/G31 are the same.

I have pictures from an article I wrote for another forum (944 Hybrid) comparing the 016 to the G31. I will post the pictures of the diff's tonight. (I don't have them on my work p/c) The diff, spider and side gears from the 915/930 is much more HD than the 016.

If you guys would like, I could post the article here. Since the G31 is based on the 915, most of it is relevant.

As a side note, a few guys on the 944 forum are running 400 rwhp with 944 turbo transaxles with good luck. But they do not do hole shots. They onlt use full throttle after the car is moving.

Since my car is powered by a Chevy 302 that is based on the old Z28's, I chose the G31 because I believe it is far stronger than the 016.

Pete

 

[Pete T]

Here are the pict's. I addrd one additional of a Borg Warner Super T-10 1st gear vs G31 1st gear. The G31/915 first gear is 5/8"wide and the T-10 is 3/4" wide.

 

[Sandy]

Excellent stuff, I got a battery for the mic, and measured the 930 gears with a bit more accuracty, the 3/4 set is 23.88mm wide at the gears teeth, and at the centers with a small flang is over 25mm. So much for plastic rulers...

Sandy

 

[jmracecar]

I read somewhere, Renegade I think, that the 915 is good for 400 hp and 350 tq but the killer is that all the ratios are miles too low for a V8. And you're right, the r&p is the weak link in all Porsche trannies but so far I haven't heard of anyone destroying a 930. I don't know the size of the 915 r&p but the G50/0x is 190, the G50/5x is 215 and the 930 is 235. My reference (Paul Frere) also states that compared to the 915, the 930 went to heavier axles and 4 spiders, so not quite sure what we are looking at here?

Maybe jmracecar would care to comment?

Cheers

Really it all depends on what you mean by "good for" a certain power level Good for two quick 1/4 mile runs? Good for 10 years of easy street use without a rebuild? Good for one race season without a failure between overhauls?

I would take issue here with the idea of the 915 being "good for" 400 hp. One of the biggest problems is the lack of a steel bearing pair retaining plate. The 930 had this. Actually the 901 had this, and they tried to "simplify" and it didn't work out too well for high-load use. The G50 had this, but the 915 did not. Wevo offers an aftermarket one for the 915. This is a "must". Without this, the shafts will spread under load. That has bad implications for all gears, the main bearings, and perhaps syncros.

So I would agree with the WEVO-modified 915 being good for 400 hp, though still only in street use and with a transmission-friendly driver.

I agree with your numbers on the G50 ring (crownwheel) gear diameters.

G50 cars also use heavier axles with bigger drive flanges. The 1989 C4 was the last of the small ones, and that was the first G64. The G50 at that point was using M10's to hold the axle to the flange, not the earlier M8 bolts.

 

[Russ Noble]

Well, that's added a bunch of knowledge and qualified other information out there.

Thanks for that jmracecar. You don't have a name do you? Like Bill or Fred or Engelbert?

What do you (or anyone) know about the "drop through" test for checking bearings in Porsche, specifically 930, trans? I presume it's a sized mandrel and is used to check the needle bearings? Presumably if it drops through, replace the bearings, if it won't fit or has to be pushed through, the bearings are deemed to be fine? Any idea of sizes? The drop through test was just mentioned to me in passing, but I have no further details.

Cheers

 

[Pete T]

The 915 uses the same bearings as the 930 and the retainer plate for the 930 will bolt in place of the 915. The 915 used a two piece retainer (same as G31--80 924 turbo) and the 930 used a one piece retainer (same as 016Y--70 924 n/a) I don't know why they did this. I have both retainers and their are cmpletely interchangeable. There is also a billet aftermarket one available.
I would tend to agree that the 915 can take 400HP. The weakest part is the early R & P's. The 8:31 late R & P is the strongest. There are a lot of V8 powered 911's and 914's with 915's.

Pete

 

[Bill Musarra]

Russ,
I believe the drop through test has to do with the case bearings.Could be wrong. If you remember the mess I went through with my 930 was all because my shop mechanic was not familiar with this test. He thought they had scrimped on the rebuild. It is my understanding as you stated that if the test piece falls through then the bearing is replaced. Mine didn't so it was not replaced. My mechnic thought it should have been replaced because it had stains on the bearing face. Had he known about the drop through test, I would not have gone through the hassels I did in order to get mine back from the courts. See:
http://www.gt40s.com/forum/tech-powertrain-transaxles/18166-930-saga.html
my saga of a 930.
These bearings are very difficult to change out. There are minimal forces that are exerted on thier face and last through one or two rebuilds. I am sure there are some here more knoledgeable than I who could tell you more in detail.

Bill

 

[Russ Noble]

Thanks Bill, it was actually one of our email exchanges over my purchase of your old 930 that alerted me to the "drop through" test initially. What I'm hoping to find now is the size of the test mandrel.

Cheers

 

[Pete T]

I've heard of the "drop through test" too but have never been able to get anyone to giveout any info on it. I do know that in order to get the new bearing race into the case, you need to heat it relatively hot and freeze the race. I don't recal the temp, but it is in the factory manuals. I've seen and heard of many people just pressing these in at room temp. If you do that I think you will destroy the bore in the case.

Most of the load is on the four point ball bearing. (the one held in by the retainer) The cylinder roller bearing takes the side loading.

 

[jmracecar]

Thanks for that jmracecar. You don't have a name do you? Like Bill or Fred or Engelbert?

Cheers

Hey Russ- Joel Reiser... I'm on the PCA National Tech committee (see www.pca.org/tech). I handle questions on the 964, 993, and 996 models, including the GT3 & Cup cars. I don' t know as much about the earlier cars as the later ones.

I also race a couple of 993's, one has the G50/3X trans, the other has a G64/51 converted to a G50/54. Both have external oil cooler with filter, pump and aeroquip plumbing. I ran in ALMS in 1999 and early 2000, now just regional amateur fun stuff. And I take care of other people's cars, suspension, brakes, track wheels & tires, etc and specialize a bit in engine & trans.

 

[Pete T]

If anyone is interested in the power that a 930 transaxle can take, check out this car! 400 small block Chevy powered, 10.10 @ 148 MPH.

Excelsior Motorsports

 

[Russ Noble]

Interesting one, Pete.

They don't appear to be running a billet side plate either, but they are on road tyres.

Nevertheless, one of the photo's shows the front wheels in the air so they must be getting a fair bit of torque to the ground. The trans is inverted too so the motor will be sitting relatively low making it all the more difficult to lift the front. Although front end lift and weight transfer probably occur more as a designed in result of suspension setup. I'm afraid the technical nuances of drag racing are largely lost on me!

Wonder what it weighs?

Cheers

 

[Pete T]

I have the original article in an old Turbo and High Tech Cars and it states that the car weighs 2820# and has weight dist. of 48/52.

Drag racing is usually hard on the drivetrain because of the dropped clutch starts. It suprises me that he hasn't broken any axle shafts. I used to drag race a 12 sec. 64 GTO in the mid 70's so I know first hand about breaking drivetrain parts.

Pete

 

[Sandy]

Interesting one, Pete.

They don't appear to be running a billet side plate either, but they are on road tyres.

Russ, the fronts look like street tires, but the back are definitly 'wrinkling' so I'm guessing slicks of some sort. But doesn't really matter as that car likely is punishing the box pretty well running low 10secs in the quarter. I think we are ok with the 930 for much of what we will toss at it

Sandy

 

[flatchat(Chris)]

If anyone is interested in the power that a 930 transaxle can take, check out this car! 400 small block Chevy powered, 10.10 @ 148 MPH.

Excelsior Motorsports [/QUOTE

A perfect example of "Take ya Porsche and Chev it"!

Oh! and does anyone have a 930 trans that they want to part with ???

 

[Russ Noble]

Flatchat, they come up on ebay fairly regularly but they are getting dearer. This one eBay Motors: PORSCHE 930 TURBO CLOSE RATIO TRANSMISSION (item 300054322806 end time Dec-04-06 14:42:49 PST) sold yesterday for US$3150

Cheers

 

[Ron Earp]

Sheet!

I have been thinking about one of those for the Lola for quite some time. 4 speeds is more than enough and I like the bullet proof nature of them. But that one is actually pretty reasonable from some I've seen.

R

 

[Bill Musarra]

The going price over the years is about $3K. If you see one that needs a rebuild, then you can get it for less. My car came with a 930 in it. I took it out to my frienly Porsche shop forman who told me that most of the trans with about 40K miles need rebuilding as the dog teeth get pretty worn. Syncros start to go about then as well. The case bearings need to be tested with the drop through test to see if they need replacing but that is pretty rare. Very difficult to change out. The case has to be heated and the bearing frozen and then pressed in. A typical rebuild will run about $1500, which is what he quoted me. One rebuilt came up on ebay and I won it for $3000. Sold mine to Russ for $1500 and now I have one for what it was going to cost me for the rebuild. The guy was a real neat kind of guy. But it all has a story. See http://www.gt40s.com/forum/tech-powertrain-transaxles/18166-930-saga.html?highlight=saga
The ratios are just about O K as is. Some might want to tweak them. There aren't a lot of ratios out there if memory serves me. They do come in a long and short version. Can't remember right off what makes the difference. You want the short one though, so it doesn't stick out the back. I was warned also to use only the lsd trans fluid. No substitutes. You will know it because it smells worse than a 4 day old diaper pail.

Bill

Bill

 

[Sandy]

That was a good deal if all parts rebuilt. The main reason is that it has the LSD, which I can say I have hit 2 and were supposed to have it but none did when cracked. The don't know about the other gear ratios, but you can get most any that you need, I did mine with close ratio 3/4 and the gears sets are in the $800 range per set if I recall (read as ouch), new LSD quote was in the $1200 range. All the rest of the accessories (oilers, side plate zing you more) The stock ratios look very good for a V8 as I recall, likely very good for a nice stroker motor.

My Ratios
4:22 Final
2.25 1st
1.30 2nd
1.00 3rd (Stock .89)
0.83 4th (Stock .63)

Ron I was thinking along the same lines, who needs the 5/6 speed, it would just be more likely a chance for another missed gear


Sandy