3.6 mated to 1980 915 needs cooling

[thotdoc]

We installed a 1995 3.6 into my 1980 street/track set up 911. Now that it's all back together and running well, I'm realizing I need to protect the transmission for track days.

I get the need for a radiator/cooler and pump, which I hope we can do with the trans in the car. Is there anything else?

Will the radiator/cooler be enough? Or does the transmission need structural reinforcements?

Thank you in advance.

[DRACO A5OG]

Did you do any upgrades internally i.e.minimum the one piece bracket or the beefed up diff plate or updated to newer beefier axles?

[winders]

I would add a Wevo bearing retainer plate and side cover. I would also consider switching over to a 10mm bolt CV setup inboard and outboard. The 10mm bolts never seem to come loose while the 8mm setup always seems to need attention.

I don't think you need a cooling kit as long as you run Swepco 210 and change it after 15 or so hours of hard track time.

[Bill Verburg]

Originally Posted by thotdoc

We installed a 1995 3.6 into my 1980 street/track set up 911. Now that it's all back together and running well, I'm realizing I need to protect the transmission for track days.

I get the need for a radiator/cooler and pump, which I hope we can do with the trans in the car. Is there anything else?

Will the radiator/cooler be enough? Or does the transmission need structural reinforcements?

Thank you in advance.

Wevo Sidecover

Wevo Bearing Retainer Plate

Wevo 915 Cooler, the longer your runs are the more this is desired

[Jack Olsen]

Solid advice. I've got a magnesium-case '77 915 that's been mated to a 3.6 for 17 years now. I go to the track at least 10x per year. (Yikes!)

You'll only see elevated temps from track driving. But gear oil breaks down at a lower temp than most of the engine oils we run, so a cooler is pretty important. I have a pump and a radiator on mine (as well as the side plate and bearing retainer).

[winders]

Unless you are doing extended track sessions (45+ minutes at a time) at sustained high RPM, a trans oil cooler is not very important. There are a bunch of race cars with 915 transmissions up here in Northern California that have 3.6 engines putting out more torque and HP than a stock 3.6 that survive just fine with no trans oil coolers. Come out to a PRC race weekend some time and check out the cars.

I doubt that any of you with a 3.6 are stressing your 915 more than I am. The only problem I have had is breaking the nose off of a 930 ZF chromemoly diff (replaced it with a Guard unit) and synchro system wear from shifting too quickly. If I were going to get into endurance racing, I would certainly put a trans oil cooler system in place. But, if you run less than 45 minutes and you use Swepco 210, you will be just fine.

[3rd_gear_Ted]

What type of LSD is being used?
What ratio version of 915? (915/64 for me)
My car is the same year and the 94 3.6 engine was rebuilt by I.G.
I use Ford Escort CV axles

[SCOTITUDE]

Originally Posted by winders

Unless you are doing extended track sessions (45+ minutes at a time) If I were going to get into endurance racing, I would certainly put a trans oil cooler system in place. But, if you run less than 45 minutes and you use Swepco 210, you will be just fine.

+1 on what scott said from a second scott.
Same setup, swepco 210 and no overheating or gear oil breakdown issues.

[Mahler9th]

I have run a 3.8 with about 350-375 bhp and lots of torque through a mag case 915 with excellent Guard Transmission parts in a racing application for a number of years... about a decade.

Hottest ambient conditions 90-100 degrees, and longest races about 35 minutes.

I used Redline NS for years with only annual changes. No thermal issues. No issues with slipperiness, but I am a careful shifter (usually double clutch).

I am now trying the Swepco 210 for grins. I do not intend to change it more than annually.

Several folks I know that went to the trouble and expense of adding a cooling system with a thermal set switch realized afterward that their pumps never ran in most races in most conditions.

Just not necessary for many folks and many applications.

[Jack Olsen]

Are you guys with no issues seeing your actual temperatures on a trans temp gauge? I don't know know how much heat is too much, but I run sub-30-minute sessions, usually -- and I've got a gauge showing me my transaxle temps.

With the pump turned off, I've seen the transaxle get hotter than the engine.

Now, the experiences getting posted here would suggest that's not a long-term problem. So take my data for whatever it's worth. But I can't see the harm in keeping temps lower.

[Bill Verburg]

trans oil is like engine oil it thins w/ temp rise and eventually becomes ineffective

I agree for 30min runs a trans cooler is probably not that useful, Around here w frequently get hour or more long runs, I usually have to come in for fuel to do a complete session.

Here's some data about some of the trans fluid mentioned here and and in a concurrent thread



and here's some data collected at WGI, the trans is a g0 but the temp curves will be similar to a 915. This trans cooler has a t'stat set @~100C

[Mahler9th]

Again:

"What something is worth depends on what you compare it to."

The potential harm is to the pocketbook. No one knows the critical temp to derive benefits.

Perhaps better to spend the money on more seat time focused on treating the 915 better in terms of shifting process.

My use case is the same as Winders'. Race car with big sticky 14 inch wide slick tires and lots of torque. Mag cases. Very nicely designed and made Guard Transmission gears and diffs. Works of art.

Most races are 25-35 minutes. I consider a 60+ minute race or DE session a different animal.

No need to measure the temps. Some friends have used switches like the one included with the excellent Wevo bottom cover. After they went to all the trouble and expense they discovered that the set point was barely ever reached in a race in warm to hot ambient conditions.

The best system design I have seen for tranny cooling in the aftermarket is the one that Wevo have crafted. So if I were going to add cooling, I'd use that design as a basis. Wevo is a top notch company with excellent products and people. Well engineered stuff.

I have planned for cooling many times in the past 17 years, but never pulled the trigger. I have always found something else to spend money and time on.

But again, most of my time with this config has involved the use of Redline. Many folks find it too slippery, but since I am usually a pretty careful shifter, I have likely experienced thermal benefits without too much downside.

Since the OP lives in Napa, I can encourage a visit to Sears Point at the end of October for the 17th Annual Porsches at the Point. I think Winders and I will both be there racing, and part of the area Porsche "brain trust" will likely also attend. That is folks from JWE/JWM and Reno Rennsport.

I think there will be one or more DE groups at this event, so come on out and drive or at least visit!

[Jack Olsen]

I'm not an expert on this topic.

However, I asked about it once, 14 years ago, and got input from Paul Guard, Hayden Burvill, Grady Clay and the Technical Product Manager from Swepco. (The BBS had heavier hitters back then.)

Here's the thread:

Gear Oil Max Temperature

Hayden and Grady both said 180F was ideal for non-synthetic oil. (I don't think this is possible on a track without a cooler. In Bill's data log above, the tranny gets to 180F in 8 minutes and 20 seconds of driving.)

Swepco's tech guy said it should not exceed 250F.

Guard was the least specific about temps, but pointed out that bringing them from 275-300F down to 240F doubled the life of 996 GT3R 3rd gear sets.

But I might be summarizing poorly. The thread itself is not very long.

[winders]

Originally Posted by Jack Olsen

Are you guys with no issues seeing your actual temperatures on a trans temp gauge?

We are seeing no issues inside our 915 transaxles. No excessive gear or ring and pinion wear. No synchro issues. No problems with seals. No problems with gear oil, in my case Swepco 210, being over heated. So no reason to have a transaxle temperature gauge.

The PRC is mostly air-cooled 911 race cars running mostly 915 transaxles. There are a lot of years of experience there amongst many shops. Most of the racers are using Swepco 201 or 210. Swepco 210 is better for a race car.

Unless you regularly run more than 45 minutes sessions, more often than not, it seems that using 915 oil coolers is akin to running Big Red brakes on a 2300 lbs race car. It's overkill.....

But you go right ahead and spend all that money on a nice WEVO 915 oil cooler kit if you think you need to do so. It certainly doesn't hurt to have one installed.

[Mahler9th]

I have read that thread many times. I have consulted with Paul Guard (and the current owner of Guard Transmission, Matt Monson) in the past on many topics. Outstanding resources.

I first met Hayden back in the 90's... he has helped me many, many times, and he is an expert.

Aren't really enough superlatives for Hayden/Wevo, Mr. Guard and Mr. Monson.

I have a friend and that is also an expert. I bought my car from him and he does my engine work. He recommended the Red Line when I bought my car from him in 2001. He was using it in his 3.8L TT tranny, and various 915's he mated with pretty high output air-cooled motors.

He and his shop (Reno Rennsport) have a lot of customers racing here in NorCal. Probably more than any other shop in terms of active racers.

Most would not recommend Red Line for Porsche synchromesh transmissions. Most would also not run 911 SC fan/alt assemblies on 3.6 cases... why do we do it?

Back 14 years ago, many were afraid to use mag case 915's with 3.6+ displacement motors, whether stockish or race configurations. Now we know more.

Many answers in these forums should start with... it depends. Here, Winders and I, along with several others have shared our experience and use cases.

In mine and Winders', thermal degradation of tranny oil with pretty highly loaded 915s has not been an issue with respect to failures nor wear. That could be because other factors cause parts to require replacement before any long term effects of higher heat. But in any case, it is what it is.

Active racers with configurations seeing equal or tougher conditions don't feel compelled to install coolers. A few that have noted that switches set to 180 F never started pumps in short ~30 minute races.

Like I said before, if the OP wants current-day perspective from experts, come on out to Sears Point at the end of October. One thing you will see is that most, if not all of the current JWE/JWM racers have coolers.

These cars are spectacular, and the folks that build them are experts. And the guys that race them are great comrads. I suspect that one reason they have coolers is that they like to configure things for the occasional enduro. Plus the cars have... well, everything (allowed by the rules of course)!

The $1-1.5K the owners spent for cooling systems are a drop in the bucket on a $150k+ build.

For me the investment would be about $500, but I'd have to get $500 back in longer tranny life. So no.

Now if I needed to use fifth gear for longer stretches...

[wildcat077]

Van Svenson has a do it yourself tranny cooler setup in the Rennlist 944 forums , using a Tilton pump and a few fittings ... looks pretty simple and i'm going to do it for my 944 over the Winter.
Just another option ...

[thotdoc]

Originally Posted by DRACO A5OG

Did you do any upgrades internally i.e.minimum the one piece bracket or the beefed up diff plate or updated to newer beefier axles?

There are no internal upgrades.

[thotdoc]

Thank you

[thotdoc]

Originally Posted by winders

I would add a Wevo bearing retainer plate and side cover. I would also consider switching over to a 10mm bolt CV setup inboard and outboard. The 10mm bolts never seem to come loose while the 8mm setup always seems to need attention.

I don't think you need a cooling kit as long as you run Swepco 210 and change it after 15 or so hours of hard track time.

Thank you for the information.

[thotdoc]

Originally Posted by Bill Verburg

Wevo Sidecover

Wevo Bearing Retainer Plate

Wevo 915 Cooler, the longer your runs are the more this is desired

Thank you...You guys are making the site do its work. I'm getting the information I need.