transaxle temps

[Jim Cowden]

Not something I have ever measured is gearbox temps
Since the maiden voyage at the track a few weeks ago I have made an under tray and I have been told it will send the trans temp up.
I am thinking around the same as eng oil temps 80-90c but that is a guess.

Any advice
Jim

 

[Julian]

I also recently installed a full engine bay undertray recently. But didn't measure temp before or not yet either now tray is installed. Since supersprints are only 2-3 laps I am not too worried about it and am using synthetic trans oil. One simple way to measure max trans temps on a track session is to get self adhesive tempeture indicators. Caterpillar make them for their heavy equipment. Search the net and you can find sellers or try your luck with your local cat dealer.

I am taking mine to wanneroo raceway next week for the Australian festival of speed to try and knock off all the ferrari and Porsches, so will likely point my infra red temp gun at the trans after a few laps and see if it is reasonable. I guess about 80 to 90 deg.

 

[Mike Drew]

A friend instrumented his ZF in his Pantera, and was surprised to see that temps were quite a bit lower than engine temps. Engine temp was about 200F on the racetrack, and gearbox temp never went over 160.

Gearbox coolers might make sense for endurance racing where the cars are going flat-out for 24 hours at 200 mph, but for most of us they are probably a total waste of time.

Engine oil coolers, on the other hand, are valuable (perhaps even a necessity) if the car sees hard track use, even in sprints.

 

[Clayton]

Have used the RS components temp sensitive labels before and worked well.
Only a few $ each and available in a large range.
Process Control | Sensors and Transducers | Temperature Sensitive Labels

Clayton

 

[Howard Jones]

I have run my GTD with a R21,360Hp 302,Quaife upgrades and TBD on street tires, in it on very hot summer days here in California. One particular day it was 105F and the sessions were a little longer than usual. 30 mins instead of 20. The last run in the afternoon was the hottest and I began the session with a gearbox temp of about 95F. This was a result of letting the car cool down after a session about an hour before and having run 3 total sessions on the day for a total of about an hour and a half.

Gearbox temp at the end of the final session was 160F. I did not run my pump except to take a temp reading at the end while sitting in the paddock. I have concluded that a gearbox cooler is not needed in track day cars that run typical 30 sessions. However a pump that delivers oil to the necessary spots in the gearbox would be a good idea. In my case I have a cooler and a pump that returns half to 5th gear and the other half to the ring gear.

On the road I have never seen grbx temps above 115F. Even after a long 80mph run down the freeway for a couple of hours on a warm afternoon.

Bottom line is the cooler will remain in the GTD, but I am only going to use a pump and returns to 5th gear and diff in my SLC along with a temp sender/grbx gauge. If I begin to see temps above 190F then maybe I'll plum in a cooler.

I agree that only a long distance car or a very powerful car with a friction type LSD would require a cooler on the grbx.

Note: Friction type LSD units do produce more heat than torque bias types like my Quaife.

 

[Ron Earp]

Hey Jim,

Our T70 w/930 has generated some pretty hot temps on the race track. At a summer event on a tight/twisty track, with a real 97F day in effect, we were getting around 220-235F on input to the cooler. So, that was transaxle oil temp before being cooled. Sessions were around 25 minutes, five sessions were run, and data recorded at the end of the session. Most sessions were started with only about a 45 min time for cool down, so I'm sure we started with gearbox temps in the 160s or so.

I imagine our temps were that high due to the track conditions. CMP is a tight track so the LSD had a lot of work to do. And with air temperatures being as high as they were we'd certainly have benefited from a cooler day.

Our cooler is not located in an optimal location nor does it have a fan. When we relocate the transaxle cooler I'm sure that we'll achieve lower temperatures. The goal is to put the transaxle cooler over on the passenger side where it can get its own airflow. Right now it is sharing the driver's side opening with the engine oil cooler and the engine oil cooler is getting most of the flow. I think we underestimated how much airflow the transaxle cooler needs but we will fix that little issue.

Now with street driving I've only seen around 180F on a very hot day, again around 98F or so air temperature. And to get up to 180F took about one hour of driving, the day I took the car out to a car show. The engine has a 190F thermostat.

 

[Jim Cowden]

Thanks for the replies gents.

I did some checking as well and it seems 60-80 deg C is around the expected.
That seems to tie in with all your experiences.
I run a programable ECU and it is constantly data logging so I am going to throw a temp senser in the gearbox drain plug to monitor from time to time.
I also plumbed some air around the diff housing as the 01E is heavily finned so it has to help.

Jim.

 

[Howard Jones]

Maybe one of our transaxle guru's could tell us a little about this. I would be especially interested in the heat production differences of the different LSD types.

Ron what kind of LSD are you using for instance?

 

[Ron Earp]

Ron what kind of LSD are you using for instance?

Clutch pack.

I don't think the cooling fins cast into any of the boxes are going to offset the heat enough to make one box better than another with respect to box heat dissipation. I'd think an oil cooler is a must for any box that is going to see more than street work. Unless you live in the Nordic lands and never drive Flatout, and I know you'll be driving Flatout.

 

I fitted a permanent temp sender in place of the level plug on the side of my ZF 5DS25-2 and typically see 125 degrees from steady highway use. I also fitted an oil cooler which scoops air from under the car and the oil is circulated via an electric pump, picking up oil from a dash 6 banjo connector attached to a modified sump plug and then returns via the port on the diff cover plate which directs cool oil on to the crown wheel and output bearings.
The original transmission oil is SAE 80 but that was what ZF were recommending 40 years ago so I sought some advice from a top UK race team who prepare and race several GT40's as well as modern Le Mans winning prototypes. Their advice was to use NEO and which is a synthetic oil suitable for use with LSD transaxles. I have used it for the past three years and have seen a small decrease in temperature and with the unexpected additional benefit of a much lighter gear shift.

 

[Brian Kissel]

Chris, could you please send a couple of pictures of your scoop configuration? I have a couple of pictures in my file, but am looking for all ideas out there.

Thanks Brian

 

[wanni]

Hi all,
the problem for transaxle transmissions is to warm up as fast as possible for good confort shiftings and to keep than the oil temp in the sump at about 80-90°C while driving. peaks of temp up to 120°C will be reached while stopping the vehicle ( pay toll or refueling ).
GL5 oils are very agressives against the rubbers and more and more by increasing the ambience temp.
The oil is protecting the gears with a film which becomes thinner while the temp is increasing. Also the oil start auto burning at around 170°C.
On top of the ambience temp. there is the INSTANT TEMPERATURE generated between the gears under load which depends from the geometry of the gears.
Do not use cheap oils. With synchros use 75W90 GL5 and with dogs use 75W140.
To cool down the temp. you can adopt an electric pump ( TILTON ) sucking from the drain plug, and forcing the oil through an air cooler and returning in the sump from the level control plug. Better to control the pump start with a temp sond which starts the circulation at 95°C and stop it at 75°C.
Regards

 

[wanni]

Hi all,
the problem for transaxle transmissions is to warm up as fast as possible for good confort shiftings and to keep than the oil temp in the sump at about 80-90°C while driving. peaks of temp up to 120°C will be reached while stopping the vehicle ( pay toll or refueling ).
GL5 oils are very agressives against the rubbers and more and more by increasing the ambience temp.
The oil is protecting the gears with a film which becomes thinner while the temp is increasing. Also the oil start auto burning at around 170°C.
On top of the ambience temp. there is the INSTANT TEMPERATURE generated between the gears under load which depends from the geometry of the gears.
Do not use cheap oils. With synchros use 75W90 GL5 and with dogs use 75W140.
To cool down the temp. you can adopt an electric pump ( TILTON ) sucking from the drain plug, and forcing the oil through an air cooler and returning in the sump from the level control plug. Better to control the pump start with a temp sond which starts the circulation at 95°C and stop it at 75°C.
Regards

By opening a NACA duct under body flushing external air around the box is a good solution. The flux increses together with the speed. The speed is generating most of the heat.
Again Regards

 

[John Fitzpatrick]

Here's an early example of a rear tray, but no info on it's effect on transaxle cooling.

 

[Cliff Beer]

Probably just reciting what has already been said here, but, my experience with durability of the transaxle in a competition setting is that it's equally important to both a) keep temps down, and also b) keep the fluid moving and continually flowing to the hot spots (bearings and gear teeth). An external cooler certainly helps with a) but may not be necessary with proper flow (though both is best for competition no doubt).

I did read somewhere that a transaxle-based LSD with friction plates will make less heat than one with torsen gears, although, I have no data or experience along those lines. That seems to make intuitive sense, but no idea if it's a meaningful difference or even relevant. As far as I can tell, most hard core amateur racers are using friction plate diffs rather than torsen.

Just my $.02.

 

[Jim Cowden]

I am regurgitating this because i have know tried tray and no tray.

NO TRAY
Eng water temps all day 86-90 c
Oil temps 80-90 c
gear box temps max 91 c

with under tray
water temps 102.5 c in 4-5 laps
gearbox 117 c
eng oil 130 c

sollution, undertray removed and material recycled into a bigger drysump tank.

All measurements were data logged through ECU

Jim

 

[Ron Earp]

Were the daytime temps similar (within a couple of degrees) for the testing days? Or were the tests done all in one day?

 

[Jim Cowden]

Testing was on seperate days within 2 weeks of each other and the day the tray was tested was about 3 deg c hotter.

I personally could not justify a larger oil cooler (eng) and fitting trans cooler and pump.I felt the added complexity was not worth the undertray.
Speed wise it made no noticable difference on the day but it did make the car more difficult to work on and jack up.
Others may have different results but that was what I concluded.

Jim

 

[Troy]

Handy info Jim. To what extent did your undertray extend. Presumably from the back of the drop floor section to rear chassis rail?

Any pics of the new dry sump tank and where you've fitted it?

 

[Jim Cowden]

Hi Troy

The tray did start at the rear of the floor (rear bulk head) traveled to the gearbox and rolled up at the rear towards the gearbox and finished at about the rear clip hinge area.
Width wise it was attached to the rails the eng mounts attach to.

Jim