930 failure?

[Russ Noble]

There's been mention of 930's lately in different threads. Personally I think they are far and away the best trans available for the money.

I have been wondering though, if anyone knows what it is that fails in one after they have been fitted with spraybar, cooler and billet side plate?

To my mind the input shaft looks a little puny, is that likely to be a problem with all out racing starts, with a high hp/torque motor, on 14" race rubber?

Does anyone know of of one successfully withstanding this sort of repeated punishment? Or alternatively anyone who has destroyed a 930?

Cheers

 

[Sandy]

Yes, would be interesting to hear if any have blown. I have one sitting in my garage and it looks pretty beefy from the outside, hopefully the guts are as strong. I have it going on the RCR with about 620hp and the 14" Avons, so would be good to hear as well.

Sandy

 

[Sandy]

Here a a couple of images of the inside of a 930 before build...

Hard to get a scale on things, but looks like gears are meaty (subjective I guess).

I also got off the phone with Roger at PowerhausII and asked if he has seen a failed (due to blown R&P or gears) 930 trans and said no. The only one he has seen blown was due to a clutch explosion that cracked the bell, FWIW. He did mention that it is a very stout trans with all shafts supported. Most repairs were sliders/syncros.

Sandy

 

[Russ Noble]

Thanks Sandy, I've been following your setup with interest. When do we see yours on the track? I'm hoping for similar hp to yours but slightly more torque/less revs. Harder on the trans particularly in the higher gears when there's no wheel spin.

I haven't really got any concerns about the internals it was mainly the input shaft. Approx 22 mm diameter (7/8" for those who still have funny measurements!)

Anybody know how the input shaft compares with the other high torque trans. eg ZF, T44, LG600?

Cheers

 

[Pete T]

The 930 has a 1" (23mm) x 23 spline input shaft. I don't know about the others but many Chrysler muscle cars used the same size, so I wouldn't expect it would be a problem. The G50 also uses the same. The 915 uses a 3/4" (19mm) x 20.

 

[Sandy]

Russ -

Hopefully will have the car by year end and can get to work on it. Most of the hard stuff will be done, but will still have a load of wiring and plumbing to get it ready. I would love to see the guts of a ZF, and a 5052 for comparison. The 930 R&P section of the gear box looks huge compared to the other, not sure if it is all that, but I'm guessing it will be ok. But being paranoid I have a spare ;-)

Sandy

 

[Russ Noble]

Thanks Pete T,

The shaft necks down to 22mm behind the spline, seems a bit on the small side. Time will tell. At least no-one seems to have had problems yet. Sandy might be the first! LOL

Sandy,

Yeah, I've got a spare as well, hope I don't need it though. Wasn't intentional. About the same time as I was finalising a protracted deal on one from the States, one was brought into my work here. Couldn't turn it down, any decent transaxle is virtually unobtainable in NZ.

Also before I'd bought either of the trannies I picked up a brand new r&p on ebay for $200. Cheap insurance. You know how it is, if you've got it you won't need it.

Cheers

 

[Jac Mac]

Russ,
Input Shaft Size:
Ford Top Loader ( std small ) 1 1/16" x 10spline usually fails with around 450 ft lb on 2700+ lb car and 15" wide rear slicks.
Jerico- Super T10- Rankin etc have 1 1/8" x 26 spline, unusual to have failure in similar situation although big blocks will kill them with torque @ lower RPM.

Larger spline number spreads load more evenly around shaft as well as splines being shallower increase's root dia of spline area.

Found as soon as we started using Tilton 3 plate clutch's old Top Loader style trans started to fail, that had been reliable with older twin plate cushion hub, and non-metallic type clutches.

Bear in mind that these are front engine/rear drive examples.

Jac Mac

 

[Sandy]

Jac Mac -

Were those failures as drag race cars or road race?

Sandy

 

[Jac Mac]

Jac Mac -

Were those failures as drag race cars or road race?

Sandy

Sandy,

They are Road Race, using standing starts . The input shaft develops a twist in the spline area, which some some drivers with a bit of savvy notice as a clutch drag problem before the shaft fails .

In your 930 and many other trans with a shaft dia smaller than the spline area this may be a plus. Also as the input shaft is nearly twice the length of a normal trans it will act as a torsional shock absorber for the trans to a larger degree. Any attempt to beef up this shaft will just transfer these loads directly into the trans gears. The Porsche Cup cars have a 'weak' clutch for this very reason.

Jac Mac

 

[Russ Noble]

In your 930 and many other trans with a shaft dia smaller than the spline area this may be a plus. Also as the input shaft is nearly twice the length of a normal trans it will act as a torsional shock absorber for the trans to a larger degree.
Jac Mac

Comforting words Jac Mac. In the absence of broken input shafts all around the world, I'll put my worry beads to work on something else Give it all it's got Sandy!!

Cheers

 

[Sandy]

Will do, I am not a carefull shifter, and as such welcome the 4 speed, good to here from Jac Mac as I do value his input. I remember one of the older Doug Nash 5 speeds could be ordered with a 'torson' bar that was supposed to help with gear shock for drag racers.

Russ, thanks for the confidance! I'm happy to be the guina pig in this case as I can tell you that I will have at least one burnout on the Avons for a picture Might make it a bleach burnout just for show. Boy that sounds wrong for a GT40, but might as well get it out of my system. How about start worring about the CV's and half shafts, seems like a good next venture!

Sandy

 

[Russ Noble]

How about start worring about the CV's and half shafts, seems like a good next venture!

Sandy

Jeez Sandy,

I hadn't even thought they might be a problem. Now you've got me worried!

Maybe I'll just wait and see how your destruction testing goes!

Cheers

 

[BruceA]

Yep I know this may be a bit off the subject but ... thats an interesting look in the gearbox there. I would be interested to know what the width of the individual gears are, the shaft spacing and shaft diameter are.

I went down the path of upgrading my Un1-13 box. I had a new 1-peice input shaft made along the same lines as the Derek Bell kit.
My shaft is 23 x 1" at the clutch going up to 26mm at the first bearing, atfter that it is a solid 27mm all the way to the end.
I certainly plan to use a sprung centre clutch plate as I had the shaft made with no wasting on it at all. What I found was that the original shaft 'flexed' in the middle by the 2nd/3rd gears and it could be said it was only supported by 2 bearings, due the the splined sleeve freeplay. The 1-peice shaft gives it a 3-bearing support, (crankshaft end) with less flexing due to not having the 'wasting' along the length.

The gear physical sizes in the photos of the 930 look very much like those of the UN1 box, so thats why I was wondering if someone could measure them for me (and everyone else reading.)

Heres my UN1 measurements:

Gear width 1st 20mm, 2nd 20mm, 3rd+4th 22mm, 5th 18mm (but I plan to make a wider one at 22mm.

Shaft spacing 76mm

 

[Sandy]

RL -

Sorry I didn't reply sooner, I didn't catch the last post. I don't have the box cracked so can measure the gears width. BUT the builder is supposed to send back the 3 and 4 gear set which I had changed to a different ratio. Will see how they measure up once I get them back. I'm sure the gears are one part of the big picture, how big is the question, but the fact still is that the box is as good as its weakest link so I would expect all things would have to be concidered. The R&P of the 930 looks big vs some of the other boxes, once of the porsche sites has some info on the various boxes, but can't remember which. Will post when I get the goodies.

Sandy

 

[Sandy]

Rambo-

Got the gears, and they look about 7/8" or 22mm. I just quickly measured with a plastic ruler (in inches at that). This was for 3rd/4th gear sets. I don't have measurments for 1/2 as they weren't replaced.

HTH

Sandy

 

[BruceA]

Rambo-

Got the gears, and they look about 7/8" or 22mm. I just quickly measured with a plastic ruler (in inches at that). This was for 3rd/4th gear sets. I don't have measurments for 1/2 as they weren't replaced.

Thanks for that. Interesting, to know those gears are the same size (width) as the R21 box.

 

[Pete T]

Here are 2 pict's of a 930 diff w/ring gear vs G31 (same as 915) The side bearings are larger too. I seem to remembet that the 930 gear dia. is 9"

 

[BruceA]

Interesting to note the two diff units in the picture.
Heres my observation. I assume the 930 diff unit is on the right, because you said it has a larger crownwheel gear. Correct me here if Im wrong ...
The side bearings may be bigger, that the ones on the left, (915), but there are more rollers on the left side ones. This would give a greater surface contact, reducing the load per roller.
The diameter spacing of the crownwheel bolts is also larger on the left side (915). Would this not give a greater holding torque?
Also of note is the side gear axle diameter. The left unit (915) caters for a larger axle unit than the 930 (rhs).
I also see only 2 spider gears in both the diffs. Obviously this is all that is required but I would have thought there would be 4.

So for me, just from looking, I see that the 915 box could be quite a heavy duty unit. I would guess that its just the crownwheel/pinion size that created issues in the gearboxes that required an enlargement for the 930.

 

[Russ Noble]

Rambo Lambo, the smaller number of rollers could just be a cheaper bearing from a different source. That's something to watch with all bearings when sourcing replacements.

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