new guage = new thing to worry about: transmission temps a340

[PlacentaJuan]

as per my members ride thread, i have been having problems with gear changes while the traqnsmission fluid is too hot (ie hills drive or regular hard shifting) and so installed a second oil cooler, which helped a bit but still got the same problems while driving in the hills, the most noticable being a large hesitation to downshift into 2nd gear, which is a bugger when you expect the downshift before the corner, but happens in the middle of the corner instead.

anyway i installed a transmission oil tempo guage yesterday, and used a T-piece in the return line after the last cooler.

after the 40 minute drive to work today, the guage didnt get past 37 degrees (the bloody thing is in fahrenheit so i have to convert) but according to the supra manual this is well below the normal operating temp (70 - 80 celsius) for ATF T-II, i assume the type IV is about the same (toyota fluid) which is what i am using.

now if hot fluid is my problem then the next step is to take to the hills, and expect temps over 80 degrees, but it will be annoying if the 2 oil coolers are too efficient for normal driving, but not enough for a thrash in the hills.

of course, pre-guage installation there were absolutely no problems with the transmission on normal driving, (that i could tell) but i assume there is a 'normal operating temperature' range on the fluid for a reason, so what differences would be expected if i am doing 95% of driving at half the minimum temp?

[SuperDave]

I haven't looked into gearboxes, but I know with engines you don't want to over cool the oil. Best way is to make something to block the oil cooler(s) for the 95% you drive on the street to keep the oil warm. I have to do it with my engine oil cooler. It may take some time to determine how much you need to block off, so use some cardboard so you can modify it's size. Once you have the size worked out transfer the shape onto plastic and somehow affix it to the cooler. I just use the bull dog clips to hold it in place, the design of my set-up allows this to occur with no damage to the cooler core. Then when you want to do some hard driving just remove the blocker and your good to go.

[Talasas]

Either that or you'll have to start stuffing around with thermostatic bypass into (say) the second oil cooler above a certain temperature.

[131OWN]

PlacentaJuan, what has been done to your tranny apart from tranny coolers? what power are you running through it?

The a340 second gear is engaged by having both shift solenoids activated, if one solenoid is dying it will be slow to react and there for you will have a slow gear change into second. Inside the valve body there are 3 filters, if one of there is clogged gear changes will be slow, don't just pull it apart if not experienced as it full of check balls, valves and springs. It is most problem a Shift Solenoid.

I don't believe running the tranny at 40C is going to be a problem.
If you have a proper shift kit fitted (not just shimmed) use DEX III

If you need a Shift Kit PM me
Cam

[Aphox]

Could you not install an equiv. thermostat for such an operation in line with the coolers?

[131OWN]

Could you not install an equiv. thermostat for such an operation in line with the coolers?

No you need line pressure it must flow through the cooler lines

[PlacentaJuan]

thanks supra dave i will give the blockign thing a try, the only problem is that even with both coolers unblocked i still get the gear change problems (maybe ill use a switched fan on one of the coolers)

131own the problem only happens when the box is really hot and the hesitation is when i downshift form 3rd gear to second gear.

admittedly this has improved somewhat since adding the second cooler; it used to happen on the street, but now only happens on a fast run through the hills, but this is the problem because it unsteadies the car if the gears dont shift at the expected moment.

yes it has a stage 1 (or 1.5) mv auto shift kit and last dyno gave me 240kw at the wheels, pretty sure the valves shuold be ok because mv autoes looked at it (over a year ago now) and the fluid has allwatys been good (comes out looking new, not burned and smelly like i used to get from the 1jz)

one idea i had was to use some check valves and an electrically operated solenoid to bypass the big cooler when on the street and manually swhich it (and an extra fan) when it is required.