Does anyone know the optimum operating temperature range of the 901, and/or the the temp. at which accelerated wear becomes an issue?

Porsche added a pump and cooler to the circuit of the 915 when the 3,0 911RSR passed about 300HP. Later Euro street cars (e.g. 3,2 Carrera) got coolers for about the same power level. Euro cars can see higher speeds for longer durations than typical US applications. In Any Case, US 3,2's never got transmission coolers like the Euro cars did...

It's more a factor of lubrication than anything. Unlike engines, transmissions don't make heat except through friction losses. Use a good gear oil like Swepco and you should be good to at least 250ºF or so.

If you have over 300HP and you use it a lot (i.e. track work) you may benefit from some kind of cooler. Street car maybe not.

The only time i could feel the shifting getting harder during street driving was on a hot summer day after some 600 miles through the desert.

However, on a track car with HP, a transmission cooler is a must.
Andy

Has anyone run an oil temp gauge on their 901 transmission?

Thanks Guys,

I'm always amazed with the amount of knowledge residing in this thing of ours ( couldn't resist the movie reference ). The reason I inquired is I'm running a 4.3 V-6 and its' exhaust runs closer to the case and generates considerably more heat than stock. You're replies lead me to think that although it might be a nice safeguard, it probably isn't a necessity (after all I've run it as-is for several years now), at least until I have more opportunities to really run it hard.

Scott

must be a movie I didn't see, sorry...



Aha. Radiated heat is another matter, but I'll stand by my original statement that nothing in there is gonna melt, and as long as the lubrication is up to the heat - however it gets there - you'll be OK.

If you have that kind of heat that close to the case, tho, you want to be especially mindfull of proper lubrication of the inboard CV's. Swepco 101 or LubroMoly 39. Cheap stuff will turn to clay.

For radiated heat, I think it'd be lighter, simpler, and cheaper to have your headers coated by someone like JetHot. If you still have issues after that, go for the pump, cooler, and plumbing approach.

i have a cooler and pump on my transmission plus a temp guage. The highest i have seen my temps street driving are only 150F after flipping the pump switch they fell to 135 in a few minutes.

Having the exhaust coated is definitely on the to-do list. I'm convinced excessive ambient engine compartment temps. are a major bane of conversions, shortening the life of; alternators, starters, batteries etc. I've fab'd heat shields, but aren't convinced of their efficacy.

Which brings up another question that perhaps should be asked in a new topic (if so, tell me).

Any improvements over the 75-90w originally called for? Broader Ranges? Synthetics? Additives?

Actually it's a question that has already been asked lots of times in other topics ( Search is your friend, hint hint...)


for 901/915 Swepco 201 in 75W90 remains The Hot Setup. I have been known to use 203 but this is controversial, so I mention it but won't go on record as recommending it. Porsche ( i.e. 901/915 ) synchros need friction to work right - but 203 -is- recommended for boxes with ZF LSD's so I think it's not enough MoS2 to matter. (And the boxes I used it in -already- had bad synchros so I really didn't feel too bad about it. It didn't make them worse and I felt better about reducing R&P friction.)

Mobil-1 and its ilk are great for transmissions that specify a GL-5 -- but the 901 predates that stuff. You will find people who use and recommend Mobil-1 and Redline so ultimately you get to make your own choice...

...back in 2000 or 2001, I had talked with an engineer at ROYAL PURPLE, about using their stuff in my 915. He was saying that the lubrication boundary layer was so thick that it wouldn't allow the dog faced gearing the 915 to shift easily. They had no problems with the Borg-Warner and other styles. Even with the Funny Car transmissions, that usually remove every other tooth of the syncros.
Several racers had called and conveyed their problem. Royal Purple suggested using their ATF version of the lubricant in the 901/915 transmissions. Some changed to the ATF, some didn't and changed to SWEPCO thinking that the ATF fomula wasn't up to snuff.

So I've had my car running now for about a year. I used an infrared temp sensor to 'shoot' several points of interest on my car to check cooling ability. I have installed the flaps on the underside of the car and did notice a drop on temps, as it helps evacuate the heat under the car.

Concern? or Acceptable? I did a drive the other day when it was 90 degrees here in Seattle. After street driving, I immediately used the temp sensor to check engine oil temp at the filter (186) and concerning was the transmission housing at 200 degrees. Is this radiant heat from the exhaust warming the housing or is there something else going on?

IAMCHAPPY is seeing 150 street driving. Why am I hitting 200? Thoughts?

150 to 210 is the range that my box shifts smoothest. That said there are a lot of factors into temps for any given car. Driving conditions, lube type, LSD or not, and driving style all contribute. I used an infrared thermometer for a good while but was never satisfied that I got good readings since the ground clearance limited the number of places I could get a good shot at it. In other words, there was too much variation in the readings to trust them. My temps with the installed sensor/gauge are lower than those I got with the infrared thing.

I figure the 993 engine driven like I stole it puts enough stress on the R&P that I want as slippery and cool a trans fluid as I can build into the car. The excellent clutch-type Guard LSD just furthered the cause.

Also I installed a temp sensor (shown in the thread below) in only one place, where the speedo gauge would go. That works for me because I use GPS as my speedo and don't even put a speedo gear in my transaxles any more.

Next time I take the box out I'm going to put sensors in each compartment just to see if there are significant differences.

http://www.914world.com/bbs2/index.php?sho...161520&st=0

Chances are you're fine without a cooler, even at 200 degrees if your box shifts well. I'm also convinced that there is a lot of exhaust-heat soak if the car is in town sitting at red lights and hardly moving... not much of a factor on the open road. I run synthetic fluid in mine.

Initially I used it because, with a high torque engine driven with authority, I would be protecting the R&P and they're more expensive than synchros. But I also discovered (although this is prior to having a temp gauge) two things.

1. My temps dropped about 10 degrees on average and
2. My synchro wear didn't increase at all. About that ...

Number 2 is conditional: There are plenty of folks that will tell you synchro's will wear badly and dog teeth, because the synchros don't hold as well, will suffer if you run synthetic. They might be right for most folks.

All I can tell you is that I haven't found it to be the case. But I'm certain it has everything to do with shift technique, i.e. smoothness and reasonably "slow" shifts, but I can't prove it. Not enough data points.

Good luck

Thanks you have lots of perspective and it make sense. I have not seen the temps get over 200 with the infrared sensor, suspect you're correct on the temps being lower inside. You've got the proof with your temp sensor.

Running 200 degrees on a 90 degree day after an hour of driving is expected.


Thanks!

200 is fine
street cars won't have a problem with temp


track cars will
its not entirely about the radiant heat or the torque for them
I hit 250 on my track car (with a guage) and a 2.0/6

its oil... anything approaching 230 is a problem

I don't think the speedo drive is a particularly good spot to measure temps because it does not see much oil and is far from what creates the heat.

I measure temps in the fill plug. Stock 3 liter motor running Miller's transmission fluid. It's a track only car. Without cooling, it will go north of 275 pretty easy. With a cooler and a blower on the cooler, it will run 250 if you are really pushing.

200 is pretty normal. In my experience, shifting problems start around 250+

forgot to add that my 250 is with a cooler on the track
I use redline light weight "shock proof"

I see about 105C (about 220F) on the track, 2.7 with ZF LSD and Motul FF-LSD synthetic oil. No cooler though. And no problems shifting.

I run a temp gauge in an adapter that I machined that replaces the speedo drive on my track car. I also ceramic coated the headers to assist with heat minimization near the gearbox. I'm not running a cooler.

The most I've seen is 180 deg. on a 100 deg. day after a 30min. DE session. (I'm running about 228 HP with a 2.7 6 - RS spec. I'm also not pushing the car ten tenths however.) It did rise to about 205 after coming in the second 30min. session while sitting in the sun with no breeze.

Ceramic coating the headers does affect the under side temp.