Transmission cooling wisdom

[Brotok]

Several months ago I tracked my stock '79 SC for about 1.5 hours with small breaks every half hour. The engine stayed cool, the breaks overheated some, but it seems that the transmission overheated quite a bit - since then my speedometer has been showing half the actual speed and I assume that has to do with the tranny overheating.

I now have an external front-mounted cooler on the engine, plan to duct my brakes, and am considering whether I should install a transmission cooler to make this a trouble-free track machine. Currently I am planning to continue using it for events, not for racing.

My question is: In my situation, does it make sense to go through the troubles/expense of installing an oil cooler? What are the costs, how difficult of a job is it, does it increase maintenance or affect usability of the car, and does the kind of use that I put the car through merit transmission cooling? I'd also appreciate comments on the different systems/what is best, and where to get them.

By the way, the tranny is out of the car due to an engine rebuild and I am contemplating a tranny rebuild.

Many thanks for reading.

[Steve@Rennsport]

Hi,

First, I must tell you that I've RARELY seen an overheated 915 coupled to a stock 3.0 engine since they do not produce enough torque to place excessive loads on it. I would ask you what oil have you been using in your transmission and was it filled to proper capacity?

If you really do need a cooler, I'd kindly suggest that you install AN-8 fittings in the transmission and plumb a Tilton pump with a Setrab cooler to do the job properly. Mount the cooler under the engine grille on left side.

[Flieger]

How did you know the transmission was overheating?

[ischmitz]

I bet you your speedo also only shows half the distance traveled now. Sounds like you lost some of the magnets that trigger the speedo sensor. There should be 8 pulses for 8 magnets for every full wheel rotation.

And as Steve said, it sounds unlikely that you overheated the transmission with a stock 3 liter by 30 minutes of track driving unless somehting was awefully wrong with it (oil level or quality)

As a single data point I sometimes track my Targa with a Magnesium 7:31 915 with a 3.6 and it doesn't overheat. Does it get hot, you bet. Would a cooler make sense, you bet. But I put 30,000 happy miles through that tranny so far without any issues. The only mods I have are a single-piece bearing retainer and a reinforced differential cover plate. And I don't drag-race it unless I have to beat MikeZ

Ingo

[GrantG]

This kit from WEVO has been working nicely for me. Before installing, the shifting would be far less smooth (difficult to select certain gears) on hot days and long run sessions on the track:
http://wevo.com/Products/TransmissionProducts/WevoTransmissionProducts-Cooling.htm

[Joe Bob]

Originally Posted by ischmitz

And I don't drag-race it unless I have to beat MikeZ

Ingo

Drag racing???? Never happened, you DID beat me by .1 second in an Autocross, but every one knows that ain't racing.....

[Porschekid962]

Steve, just for fun what type of gear oil do you recommend? Hot rodded and mildly warmed over street cars that get checked but not changed all the time driving in nice weather and arent pushed very hard until they are warm would probably be the type that most all here would fall into the category of. I know a lot of people love Swepco 201, I have used it along with Redline lightweight and heavyweight shockproof as well as some Lucas and Mobil 1 synthetic products.

So could you share with us your preference...

[ischmitz]

I think the consensus is that the 915 fares best with a dyno product due to its synchro design. And most use Swepco 201 so why experiment. Change is annually and you are fine.

[Steve@Rennsport]

Originally Posted by Porschekid962

Steve, just for fun what type of gear oil do you recommend? Hot rodded and mildly warmed over street cars that get checked but not changed all the time driving in nice weather and arent pushed very hard until they are warm would probably be the type that most all here would fall into the category of. I know a lot of people love Swepco 201, I have used it along with Redline lightweight and heavyweight shockproof as well as some Lucas and Mobil 1 synthetic products.

So could you share with us your preference...

Swepco 201 (sometimes # 210) only for these transmissions (901-915-930),....

Using synthetics in a baulk-ring syncromesh gearbox REALLY accelerates wear on brake bands, operating sleeves, and dog rings, even though it might shift OK for awhile. Check the price of 915 parts and the folly of using synthetics will become painfully obvious.