So as many of you know I have a 3.0 6 track car. I need to go thought the engine (another story). I have the opportunity to go to a short stroke 3.2 or keep it at 3.0. Ether way I would produce more power since I will have appropriate pistons and cams for carburation. My concern is the trans. It is a bone stock rebuilt 901. I plan on adding a cooler for the trans. I do not want to go through the trans every year. I am not an animal on the track and I know not to abuse 1st gear. What real world experience can you guys share?

Ask in the Paddock section.

I think the big thing that will kill the trans is heat, there're pump and cooler mods you can do to the 901.
But of course that means tearing down your trans again.

also for a TT car,, shorten 4th gear was a blessing in my old car.. allowed for real nice acceleration out of corners on the faster turns.

It's really pricey to build up a 915 for our cars. I would work your 914 box unless you really want to go down the slippery slope.

It's torque that kills the 901, not power.

I've got about 280flbs of torque and just over 300HP that i have been putting though my stock 901 without any issues for the last 10 years.

Granted, the car isn't a dedicated track car but does see it's fair share of abuse.

I don't use 1st gear anymore as it is the weak link. You'd be snapping that off in no time trying to lay down some rubber.
I take off in 2nd and i can still easily spin the wheels with 10" slicks for 30 yards if i wanted to.

If i can get it just right i can do 0-60 in under 4 seconds without ever shifting out of 2nd.

In full race use...

the 914 specific builder that I use, recommends a cut off of 200- 225hp as the point to financially consider a 915 box

this based on dozens of experiences with full race 914's going through 901 box rebuilds frequently versus the expense of conversion to a 915 with less rebuilds.

its a financial decision and becomes cost effective around 225hp for full modified race boxes.

I rebuilt my 901 annually until I added cooling (had no choice... it would blow up)
with cooling I'm about 2 years into this box and it hasn't blown up yet

I don't expect it to last for ever
but I'm running 180hp-ish

a spool will run less heat than a LSD, and you'd be amazed at the oil temps seen inside of a race box.

I've been very pleased with redline full synthetic light weight shock proof oil
this may be another factor helping to extend my life, as I only started using it at the same time I added cooling.

I use first gear regularly
my failures have never been with first gear
even though I have gone through at least 6 race trannys
but I also don't have 300Ft-lbs to deal with
brant

That's freaking awesome!

Thanks for the specifics Brant. That is very helpful!

no problem
and I should of added that I'm doing transmission fluid flushes every 3 events now
so about every 6 to 10 service hours..

(kinda sucks because its nearly $20/quart)

but I was reaching way over 250F on the oil in the trans prior to cooling
(depending on which sender location you measure from , and I'm using 2 different probes/locations for comparison sake)

I've changed my intake for the cooler 3 times now... improved my temps each time
currently I run 210-235F on a really hot day with the cooler



it is also my belief that RPM has a big impact on tranny temps... and what redline you are using or spinning the transmission to.

Anecdotally you also don't see a lot of tranny problems with -4cylinder race cars... but then again a lot of the legal -4cylinder cars are pretty small displacements
my ex 2.0/4 race car lost only 1 tranny in about 9 years of racing, and never ran the same shift points/rpm that I run in the 2.0/6

so I hold the belief that RPM has an impact on temperatures too... all of those bearings have to spin faster / create more heat from friction at higher RPM's

Hey Brant, do you have a picture of your curent intake for the cooler?

I left a message at Roger Sheridan's place. I just spoke with Jerry Woods. He told me that the 901 can handle a 3.2, for the street, but it is too much torque for the track. He says that a 2.8 built for racing is questionable. Outside of the know 1st gear issue 3rd and 4th gears strip teeth...

I just checked my build thread.. and apparently I don't...


my first intake was a scoop below the fire wall (about the location of the motor flaps)
this picture:

my second intake was a scoop at the passenger side targa bar/window location:

Didn't you and you dad do that one? Did it end up on the targa bar inside near passengers head? If so I saw it in your build thread

Edit: yes that's the one. I am slow on the response

currently ... (no picture)

I ditched both of the aluminum scoops

I'm running a large electric fan into the cooler with an aluminum shroud we fabricated to keep it sealed nicely...


so no intake scoop

and I measured transmission temperatures with each set up to determine the most effective.

the fan is powered on any time the car is powered on (as is the transmission fluid pump)

so full air flow any time the car is running and not dependent on road speed

better numbers because I believe both of my scoop set ups were too restrictive for my needs.

I like your set up. I am thinking of putting the cooler in the right rear fender with a scoop outside the body to force air through.

FWIW I had John Williamson (Otto) build a box for me around 2004 and it has never needed to be opened-up since. The car had a stump-puller 2.4/4 first then a 2.2S/6. Currently it has a 2.7/6 race motor putting out 190ft-lbs at the rear wheels. Only now is it showing signs of needing freshening, 2nd and 3rd gear syncros specifically.

However this box cost around $6,000 to build > 10 years ago...904 mainshaft, gears, billet int plate, LSD, machine work...

Also interestingly none of the 4 race-experienced shops that have worked on my car have felt trans cooling was terribly important. I may do it anyway and I have a cooler setup I bought from a retired 914/6 POC racer. Just haven't gotten around to it yet...

Hey Chris. Otto did my trans too! It is all stock except it has longer studs on the tailcone that have nuts welded on the front side. He said a problem for these trannys were the tail cone loosening up or pulling studs through the case. He called this his High Performance mod. I'll get a pic

I just got off the phone with Roger Sheridan. What a really nice guy! This is what he told me. He prefers the 901 and it can handle more power than its rated for. He had a 901 behind a 3.4L with 350 HP. He would go through it every other year. He had different trans geared for each of different tracks. Roger said the ring and pinion are small. Cooling is a must. His AN-6 system is plumbed into the fill and drain plugs. The cooler is in the fenderwell with no ducting. He thought just getting the oil out of the trans was the big deal. He has a Tilton pump with a switch that he manually turns on. He turns the pump on after running a few laps. Roger thought the excess oil capacity was a non issue with the pump off (in terms of overfill) He runs SWEPCO 201. His car now puts out 400HP and his has a 915 behind it. Rogers car is a tube frame car.

Brant,

When you say "it blows up" what actually breaks?

Seems to me to be a thrust issue and might be something that should be redesigned for track abuse with machined out forward seat and larger bearing for the pinion and drive shafts....

I've blown the bearing in the intermediate plate about 5 times. Causing it to "mill" out the intermediate plate bearing retainer. Eventually loosing the ability to line up the shift selectors and not go into 2nd/4th correctly.

Minimal carnage internally

I still think my situation is rpm-heat related instead of torque related.
I ran mobile 1 70/90 for 6-8 years. Followed by mobil1 90/140 for approximately 4-5 years. Followed by by redline Lt. Wt. shock-proof.

"Blow ups" due to torque are usually stripping gears in either 3rd and 4th. Been there done that...

T

High torque will also lead to galling on the ring and pinion engagement. Which leads to pinion gear failure, with those sizable pinion gear teeth bouncing around inside the gearbox.

Cooling helps significantly. Make sure to spray on the R&P just as they come out of engagement, as spraying on them going in can actually cause more damage! (The oil can't "get out of the way" fast enough was my understanding of why that caused problems.)

--DD

Thanks Dave. Which side would that be on? Top passenger side?

Also, position your pick up low and to the rear of the box. Good luck.

T

I Had 400lbs of torque in front of a 901 with the tire to hold it.. BUT I wasnt racing often. Its a stronger trani than most give it credit for.

I don't think they like spinning between 5800 - 7800 for 20-30 minutes straight..... With over 225hp ....

Plus enduros.

Frankly I don't remember!

--DD

Build it exactly like this and you'll have a fighting chance of survival...

T

Click to view attachment

Oh no, Dave! Another indication you're over the hill, meaning from now on gravity is not on your side, in fact gravity is the enemy.

http://www.914world.com/bbs2/index.php?sho...=36334&st=0

http://www.914world.com/bbs2/index.php?showtopic=177277

http://www.914world.com/bbs2/index.php?showtopic=101622

There's likely more threads....

I found one of those when I did my searches. Thanks Mark!