Van

I'm also a fan of the Delvac.

racing916

Matt,

Are you sure the pinion failure is due to the oil breakdown. It makes me think the either there is play in that shaft around the intermediate plate or are the gaskets set to the right thickness causing the pinion to be either set into deep or not enough causing the ring gear to not line up correctly.

Matt Romanowski

I don't think it's a setup problem. We have all the gauges and have set it up properly and get good measurements. It also didn't make any noise or have any problems for a over a year. We run the CMS billet intermediate plate and had new bearings.

Part of the reason I think it's a oil problem is that the bearings had a decent amount of wear as well.

Steve Weiner-Rennsport Systems

Matt,

While I understand the problem you have, I'd simply mention that I've used the Swepco in our 3.5 liter (400+ BHP) RSR & 935 (700+BHP) IMSA racers without issues as both cars had effective transmission coolers. We changed those 7:31 R&P's every two years no matter what since we were doing endurance races. Both cars has spools, too,...no LSD's.

Without detailed forensics, its going to be tough to find out the sequence of events in your failure, however I would hesitate placing blame on the oil until you have much more information.

I've seen plenty of these problems over the years,.....

Matt Romanowski

I hear you Steve, but sort of apples to oranges. The 915 in those cars has a much bigger ring and pinion. I'm sure if we put a 915 in our car we wouldn't have trouble either.

disasterman

Lubrizol per Paul Guard.

kurt M

What kinds of temps are you seeing on the trans? There is a direct relationship between temps and lubricant film values. As the temps go up the lubricant loses ability to combat shear and at some point the HP/temp lines meet and wear accelerates dramatically. More HP requires better lube films but also tends to drive temps higher. If you are not measuring temps and running a cooler I might be inclined to do so. R&P failures can also be from shock.

Matt Romanowski

All good questions. We didn't have a cooler or temp on it, but both are being added right now. My guess is that the temps were too high and that is what caused the lube failure. With the prices of 901 bearings, the extra expense for the best oil is next to nothing on the price of the parts.

MUSSBERGER

Big rubber and failure to properly rev match. Ask me how I know.

stownsen914

Good point about the temp in the trans. 901 trannies are stretched in a tracked 914 with a big motor, and heat can kill a trans for sure. A simple pump circulating the oil through a cooler can do wonders to extend the life of a 901 in a car like yours. You can plumb it through the trans fill and drain plugs if you want to keep it simple.

Scott

Plavan

This is what I did with My 901 trans cooler. Its working great. The hardest part is remembering to turn it on after the 1st or 2nd lap.

I just have a toggle on the dash that will turn on the pump and fan at the same time. I also have another toggle switch for my existing temp gauge (matched senders). Toggle up for engine temp, toggle down for Trans temp. No need to add another gauge. After the first few races with the cooler, I don't even check the 901 Temp anymore- It works that good. Sometimes I'll take a quick look at the end of the race.

http://www.early911sregistry.org/for...1+trans+cooler

67King

Well, I'm highly biased, given that I sell the stuff (i.e. full disclosure here), but look at Millers. Here are two articles from techincal magazines about it:
Race Tech Magazine July 2009, Tiny Technology: Big Breakthrough and Racecar Engineering June 2010, Grinding Back the Gears. The same technology will be in the Bryan Herta IndyCar gearboxes next year, and in all likelihood in one of the most successful F1 teams. The BTC and WRC cars that have been using it have seen their gearbox lifespan typically double, but up to four fold in a couple of cases. Those two articles I linked get into some of the mechanism for how it protects the gearboxes.

We've had one of our customers who runs a shop start converting the older 901's from the PAG based oils to our di-ester synthetic with nanotechnology. The older PAG based stuff was used because when the transmissions came out, EP additives were not as capable as they are today, and PAG was the most capable. The PAG is not compliant with typical petroleum based stuff, but conversion can be done with a simple flush (drain, add conventinoal gear oil, run it warm for a short period of time, drain and add the good stuff). If you've got the gearbox apart and cleaned up, then you are pretty much already there.

Also, I should mention heat. Due to the NT not shearing down nearly as readily as typical MoS2 types of EP additives, the transaxles tend to run much cooler. 20-25 degrees is pretty typical for closed system gearboxes (i.e. those without an external cooler). On the F1 application, they have been repeatedly and consistently measureing a 500Watt reduction in heat put into the oil.

winders

67King,

Synthetics are too slippery for the balk ring synchros.

Scott

67King

Hmm.....interesting. I'm certainly outside of my comfort zone. Peter (customer) and Martyn (Millers highest ranking tech guy) were discussing it at PRI, and that concern was not brought up. Martyn's a P-car guy, too, and was pretty familiar with the transmissions. Given that, I will follow-up on it - thanks for bringing up it, I don't know if any of Peter's cars hvae run, yet.

stownsen914

Sounds about the same as my setup. For the trans pump switch, I used a 3 pole switch and put an idiot light on the "off" circuit so when the trans pump is off, the light is on to hopefully prevent me from forgetting to turn on the pump. I usually just leave the pump on all the time though.