901 tranny failures due to HP

[iamchappy]

There has been a lot of discussion on this board about the 901's short comings when hooked up to Big 6's and V8's.

I have been running my 901 with short gears and LSD on the street with a 3.0 turbo without problems, Let us hear about your experience with mating the 901 to high horse-powered engines.

Outside of 1st gear clutch dump-age damage how did yours fail.

[red-beard]

So far no issues with the 2.7, but then it hasn't been running much.

I did see someone do a burnout with a V8 car and broke an axel at Don and Glenns, 2 years ago.

James

[sammyg2]

That was steve Malm, he broke a CV joint not an axle.

I never had a problem with my V8 901 but i didn't do burn outs in first. Second yes, but not first.

The only 901 failures I personally know about are Scott Mann in his V8 914, (but he drove the piss out of it for years) and Mike Zois, but he was clutch dumping in first and seeing how much black stuff he could put on the ground.

[red-beard]

You're right, CV joint. I seem to think that the "problems" with HP have been track oriented, with long runs, not street oriented occasional bursts of power.

[sammyg2]

I just remembered Steve Iverson telling me he had trouble keeping a 901 alive in his 914, but he was running a 3.6 liter. i don't know how hard he drove it.

[iamchappy]

Most of threads I read on 6 conversions recommend going to a 915 or other Porsche transmissions.
I hope this thread can shed some light as to the durability of the little 901.
If things can be done to it to strengthen it up further this may be the best option with those who have concerns.
First gear will always be the weak link.
With a big engine why would anyone consider stomping on it when the gear is so short anyway I hardly ever use it anymore, 90% of the time I start out in 2nd.
I made the mistake of stomping it in first with my radical type 4 punched and stroked to a 2.9 engine. First time 1st blew, second time the engine blew. My excuse is I was young and very stupid and was out a running 914 for many years.

Big torque engines will be hard on any transmission if it is beat on enough, But most 6 conversions wont have that issue.

My 3.0 turbo may be putting out as much as 300hp at 10lbs and the 901 seems to handle it just fine.

A 904 mainshaft reproduction would be a welcome part for many of us who would like to change ratios to fit our needs.

[propricer]

Running a 300+HP 327 V-8 against my bone stock 901 and, yes, there is the occasional burn-out in 2nd ... no, I NEVER sidestep the clutch and I NEVER use 1st !!

POS just wouldn't stand up and finally failed a couple of weeks ago after only 17 years !!!

I'm only going to give it one more chance !!!

[914GT]

This topic has been brought up several times before. Supposed 901 failures due to Chevy V8s or other high horsepower/torque engines seem more an urban myth than reality. Sure you can abuse the hell out of one and tear one up. But I've seen transmissions designed for V8s fail too. This afternoon I saw two other 914 V8s (not including mine). One was a 327 built almost 15 years ago and its 901 is just fine.

[campbellcj]

FWIW there are quite a few local 914-6 and 911 racers and hotrods with 901 boxes. In reality I hear about few failures, and even fewer of transmissions that were actually rebuilt and upgraded to handle the application.

And the nice thing about this transmission is they are still relatively common and cheap so if you DO break one, you can oftentimes swap it for a decent used one or get a parts-core for a couple hundred bucks. Check out 915-930 prices and it's a different world. On the flip side, if you do elect to properly rebuild any of these the costs and expertise required will be pretty comparable, and none of them will be cheap.

FWIW Ottos supplies repro 904 mainshafts. I have one in my short-geared box along with a billet intermediate plate, Guard LSD and some other mods. Not a lot of track time on it yet, but so far so good, and the 60-120mph acceleration of the car was completely transformed by the shorter ratios. Otto has a similar setup in his own monster 914-6 race car and it has apparently not been rebuilt in 6-8 years and this car still wins virtually every event it enters.

Personally I like the (light) shift action and dogleg pattern of the 901 vs the others, too. Maybe that's cuz I've been driving them for over 14 years now so it's "second nature" at this point...

[Bleyseng]

The failures I have seen were the ring and pinion which sheared off. What a mess. This can happen with a 915 tranny too though.
Both units have their own problems due to being 30 years old..

Geoff

[Dave at Pelican Parts]

Yup. Remember, it's the torque that kills the transmission--not the power. Well, and sidestepping the clutch.

Dave Ferguson, one-time 914-6 racer, once showed me a pinion gear with 4 or 5 missing teeth, and damage to the rest. He asked, "Do you know what that is?"

"Uhh, I know it used to be a pinion gear..."

"Naaah--that's a sign that I have enough torque!!"

All said with that trademark big grin on his face... He said he could get about 5-6 years out of the R&P with his 2.8L race-only motor ("over 300 HP" was all he'd say) before they'd die. BTW, he was not easy on the equipment.

He did rebuild the transmission frequently, but I got the impression that was more to change gear ratios than anything else. He was practiced enough that he could on Saturday night drive ~1.5 hours home, rebuild a box from a failed 3rd or 4th gear, drive back to the track, and re-install the gearbox in time to get a half-decent night's sleep before Sunday's race.

--DD

[PCA7GGR]

Here's a shot of my 5.5 tooth pinion gear. I took it out of my 914-6GT replica with a short geared (A-F-M-S-X) 901 with a Quaiffe LSD driven by a somewhat stock 3.2 (Chip, K&N watershields, headers and Leguna muffler). This is the first of two pinion (and mated ring gear) gears that I replaced along with a transmisison case (shot bearing races). I am not sure if the reinforced intermediate plate would have prevented these failures.

I now have a 911 RSR replica with a 2.8. It also has a short geared (A-F-M-S-X) 901 with a Quaiffe LSD. I also have an early 915 tranny that will accept the 901's Quaiffe waiting on a shelf at the shop.

[BigD9146gt]

I've seen several broken parts that were the result of higher HP motors, but most seem to be very rare. The 1st gear brutality is the most common. I have seen a couple intermediate plates after the bearings started to slip, my guess would be that the heat expantion of the alloy and the tallerance after 30 years has gone out. Plus the input shaft, few spots that are suseptible to failure. Thats about it, thats interesting about the R/P, at least those are easy and relativly cheap to get/replace.

[Sonny]

Wow, you guys use the 901 with all that torque! I broke 1st off the main shaft easily with just a 2.4E/webbers spinning it!