930 failure?

[Jim S.]

Kind of an off topic question for Russ or Sandy or any others who might know: I have heard that the earlier porsche transaxles didn't shift very well, or not very smooth might be a better word; how well does the 930 trans shift ???? If it's not very smooth, is there a remedy for this???


Thanks for any info.

 

[Lynn Larsen]

Jim,

Old style synchros did have effectiveness and wear problems and usually get replaced with steel for racing. If you are using synthetic gear oil, stop. Use the Porsche recommended dino gear oil. Synthetic is too slippery and the synchros won't be near as effective in getting the gears synched up.

Lynn

 

[Sandy]

I have heard the same for the 930's, but I am hoping that it won't be that bad. Don't need to be speed shifting I think for some of the porsche boxes you can get them fitted with straight cuts and dogs. But that may be only for the g50's. Will have to see, hopefully soon. I have been in an older 930 many years ago and all I remember was the VW'ish shifter and oddly floor mounted pedals (Since I'm an american car guy). Hopefully soon someone will get the 930 going (Hurry Russ!)

Sandy

 

[Russ Noble]

Sandy,I thought your car was going to be on the track first, I'm still six months away!

You can get dogs and a wide range of ratios from Albins in Oz Products to suit Porsche from Albins Gears

I got prices from them last year and IIRC it was only about $AU1600 dearer to convert to custom dogbox than custom synchro. Excellent range of ratios available. This was going to be a planned upgrade for me after the first season by which time I would know what ratios I would need.

Also just to add to what I posted in another thread recently. I have started pulling the 930 to bits and have measured the gear shaft spacing. 76mm which is the same as the 915. Must be the r&p that makes them the sronger box. Interestingly the G50 series has gone up to 85 mm with a smaller r&p. Go figure!

Cheers

Cheers

 

[Sandy]

Wonder how this measures up against the ZF?

Sandy

 

[Russ Noble]

That's the comparison I've been trying to come up with!

For my money a 930 dogbox with billet sideplate and spraybar/cooler is going to be miles better than a ZF. Apart from the fact that it's not an original fitment, but unless you're running a period correct replica mono that's largely irrelevant! Cost will be less, or comparable, and nicer to shift. If you start with a box that needs rebuilding anyway and rebuild it as a dogbox, you should be quids in.

Be nice if the ZF guys could come up with some of the critical dimensions for the gears and r&p but (apart from Ross Nicol) they don't seem to look inside the boxes themselves, seem to to think it's better to ship them away and wait months to get them back! So, who's got a ZF in bits at present?

Cheers

 

[BruceA]

That is interesting to note there, Russ, about the move to a wider shaft spacing and smaller r/p.
Heres my take on the ideas for the wider shaft spacing.
First, larger diameter shafts can be made - also to fit inside the gears themselves with the bearings. This also eliminates shaft bending in the intermediate gears (2nd and 3rd), a sure-fire tooth breaker. Also, (just trying to find the right words for it) is the circumference of the gears then become larger. This would mean that the way the gear teeth mesh are not as acute as smaller diameter gears.

It seems that the gear width is the same for most boxes.
My R21T box has the same size tooth width as the 930 (someone above or in another post measured the 930 ones). But looking at the shaft diameters the Porsche ones may be a wee bit bigger. I remade my input shaft as a 1-peice unit raising it to 27mm from a standard size of 23.

As for the ring and pinion. I recall reading discussions on design issues of the gearbox. The box needed to be kept low as possible in the chassis. This required the gear shafts to be lowered in relation to the centre of the diff. This then made the hypoid angle of the pinion gear quite steep, and therein issues with excessive heat and tooth strength from the hypoid angle. It also meant that the input shaft had to clear the diff unit so in some cases, transaxles had to have the shaft spacing wider to allow for this.

As for the ZF boxes, I have studied the photos of those posted on here via links, and I can only assume the gearsets are 'tiny'! I too would like to see who can measure the boxes stats and post them here for us to chat over.
I know they are heavy in weight, I lifted a few one day to make comparisons!
The only thing that does look heavy duty is the R/P set in the ZF box. The gears certainly dont - but it obviously works.

Which of course brings me to another point, how many people out there have actually 'stripped' a gear in their box. Be it a Porsche, Renault, Audi, ZF, or know of one? I know of a few Renault boxes doing the 5th gear, but when you see how small it is, no wonder!

Ok, enough of my opinions! .......

 

[CanAm Ken]

Hey, you'all....

I'm new to the site, but wanted to throw in my two cents, regarding the Porsche 930. I'm running one (930 transaxle, with LSD) inverted, behind a small block Chev (yes, I know....Chev, boo...hiss). The mill has twin turbos, intercoolers, and fuel injection, and was "soft tuned" on an honest dyno at 857 HP. The torque levels are consistant with the HP readings, and come in at relatively low (2,500) RPM. I'm running the engine/transaxle in a McLaren Mk 8 clone, at 2130 lbs wet, without driver. Tires are a sticky Potenza 335-35-17 compound. I recently added active traction control (using the ABS wheel sensors on my Corvette uprights, front and rear), to modulate the ignition timing under wheel slip. The car is a street/track car, and I drive it aggressively (the logging data on my Electromotive TEC reads 0-60 MPH in about 2.9 to 3.0 seconds).

I've flogged the transaxle over the last year, and on occasions turned up the boost even a little higher than its dyno'd runs. I've never had any problems. In the past I used to break traction, which probably limited torque loading on the transaxle shafts; now with the traction control, wheel spin in minimized but still no groans from the transaxle. I have yet to add a spray bar, but probably will pull the transaxle this Spring and get it to Powerhaus in Boulder for the mod.

My comments probably don't resolve the debate, but I thought you'd like to know the Porsche 930 (at least, mine...) has held up admirably, and I suspect it will for years to come (fingers crossed).

Pics of my car attached, for those who enjoy some "outside the GT-40" box alternatives.

 

[Ron Earp]

Hey Ken,

I like that, post some more pictures in the Can Am section, I'd like to learn more about it.

Best,
Ron

 

[CanAm Ken]

Will do, Ron--as soon as I find the CanAm section...and then "downsize" some of my other pics!

Ken

 

[Sandy]

Ken -

I already felt good about going with the 930, and after looking at your ride I'm very happy!

I have 2 boxes from PHII done with the billet side plate and oilers. I have also thought that the gears in the ZF must be small as the case looks smaller then the 930 but hard to say. Many folks with the ZF in panteras have run them hard with no problems so hard to say where they blow up at. I know Richard Timpte has a nice photo of a (Technical term coming...) messed up ZF gear set.

Ken are you running a Quaife/Torsen style diff or a clutch pack style?

Look forward to the picks as well.

Sandy
P.S. Russ you can relax again

 

[BruceA]

"Perk"...! Someone say Chevy?

Ken, What a marvellous looking piece of automotive wonderment you have there.
I assume then if you are adding a spray bar, that the gearbox is not cooled already? So the very rear mounted cooler is for the engine??

 

[John]

Hey, you'all....

I'm new to the site, but wanted to throw in my two cents, regarding the Porsche 930. I'm running one (930 transaxle, with LSD) inverted, behind a small block Chev (yes, I know....Chev, boo...hiss). The mill has twin turbos, intercoolers, and fuel injection, and was "soft tuned" on an honest dyno at 857 HP. The torque levels are consistant with the HP readings, and come in at relatively low (2,500) RPM. I'm running the engine/transaxle in a McLaren Mk 8 clone, at 2130 lbs wet, without driver. Tires are a sticky Potenza 335-35-17 compound. I recently added active traction control (using the ABS wheel sensors on my Corvette uprights, front and rear), to modulate the ignition timing under wheel slip. The car is a street/track car, and I drive it aggressively (the logging data on my Electromotive TEC reads 0-60 MPH in about 2.9 to 3.0 seconds).

I've flogged the transaxle over the last year, and on occasions turned up the boost even a little higher than its dyno'd runs. I've never had any problems. In the past I used to break traction, which probably limited torque loading on the transaxle shafts; now with the traction control, wheel spin in minimized but still no groans from the transaxle. I have yet to add a spray bar, but probably will pull the transaxle this Spring and get it to Powerhaus in Boulder for the mod.

My comments probably don't resolve the debate, but I thought you'd like to know the Porsche 930 (at least, mine...) has held up admirably, and I suspect it will for years to come (fingers crossed).

Pics of my car attached, for those who enjoy some "outside the GT-40" box alternatives.

Can Am Man:

I'm running the same engine/ transaxle combination as you are - no turbos though!

John
epper:

 

[Paul Bearman]

I've been following this thread with interest as I would like to use a 930 'box. I have sourced a 'box from France from a guy who has 2 for sale but both are missing the Diff & Diff side plate. Does this mean that the Diff is a weak point in these boxes or is this just pure coincidence?

 

[Sandy]

I think the diff is the same as the rest of the older 911 boxes, and likely it had limited slip so was removed, but who knows...

Sandy

 

[Pete T]

The 930 shares the diff with the late 915. It's not a weak piece. Someone likely pulled it to use in another transaxle. The side cover is unique to the 930.

 

[Lynn Larsen]

Paul,

You might want to use a billet side cover anyway once you get a diff. They are generally stiffer and offer better management of the seperation load of the crownwheel and pinion gear assembly under high power loading.

Lynn

 

[Paul Bearman]

Does anyone have drawings/dimensions for these side plates? If anyone has a 930 diff I would also be interested.
Is the 930 'box mounted as per Porsche installation or does it have to be inverted? I haven't received the 'box from France yet so can't visualise it's appliction but I would be interested if anyone could share their installation experiences of the 930 'box.
Many thanks in anticipation.

 

[Sandy]

The box run inverted in the RCR. I have the billet side plate on a the 930's I have I think they are around $380 usd when I had them changed. Easier to just get the part from one of the porsche folks, PHII, Guards also may have them or make them.

Sandy

 

[Russ Noble]

Paul,

We will be making a billet side plate for my trans in the next few months. If you can wait til then I can give you accurate measurements.

Cheers