Thread: What is the proper operating temp zone for a 700R4

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I was wondering what the proper operating temp of Tranny fluid would be, someone mentioned that "foaming Fluid" does not disappate the heat very well. How much temp difference does having the TC Locked and Unlocked have?
How important is having an external tranny cooler? How much difference in temp should that make? Would boiling tranny fluid bust seals? How much PSI should the Tranny Fluid be under when vehicle at Idle and Running, what range are we looking at here? How do you determine the size of the Tranny Cooler required, is there a formula?

Any info is appreciated thanks.

Hey Smoke - cold you give us a few more specifics?

Several things. In a "standard" configuration say in a 3/4 ton GM pickup pulling a 5,000 pound trailer it is not out of the ordinary to see the fluid in the 180-200 degree range in "Drive" - it may go to 225 degrees on an uphill pull. If the truck was purchased with a "trailer-tow" package that includes an external transmission cooler, the fluid would be typically 170-185 degrees under most all conditions.

In a car, say a Chevelle or Impala size - the temperature should be in the 170-185 degree range at most times.

If these temperatures can not be maintained, there may not be enough cooling capacity. Prolonged temperatures above 190 can cause damage - especially to stock soft parts.

Is yours a "stock" configuration?

If you have lots of foam - that's a bad sign and you are absolutely correct, it does not remove heat nearly as well as fluid.

Is this a recent problem? If so, are you sure that the fluid is clean, of the correct type and at the proper level as determined by the dipstick - checking warm in "Park" or "Neutral" with engine running (please be careful as even at it's normal temperature the fluid is very hot and will burn if it squirts out of the dipstick tube!)

If this is a new or transplant unit, you may need additional cooling. I'm a fan of another radiator unit but a deeper, finned pan may fit your application as long as you remember you now have a new "low spot" under the car and don't try and straddle any big rocks!

Other will chime in - but this may get the creative juices flowing.

Regards,
Glenn

As I posted some time ago in another thread, here is my 700R4 transmission cooling problem: First, when you are driving down the road, you probably will not have a cooling problem. In overdrive, the converter is locked up so there is not much heat being generated. Where the cooling problem will show is at slow speeds....putt-putting around the fairgrounds, etc.

I did the following steps with my 350 Chevy/700R4 with no radiator trans lines:
1. First used a flat Derale cooler with a fan mounted horizontally over the rear axle. Blew the air downward. Long pulls in lower gears made trans temp go to 260 deg.
2. Added finned aluminum cooler (long skinny tube with fins) outside of frame rail. Zero change.
3. Added high velocity boat bilge fan blowing down tube cooler. Zero change
4. Moved Derale cooler from under car to above rear tire (this is a 4500 lb jeep). Helped some but long pulls still got hot.
5. Removed bilge fan. No change
6. Changed to Torco synthetic fluid...figured if it was going to get hot, then I should use a fluid that would take the heat. This helped probably 30 degrees on the long pulls. I am at 11 quarts in the system right now.

As soon as I quit the slow pulls (unlocked converter), the temperature falls to under 200.

From what I can tell, you cannot predict the performance of a system by asking other people...it is a personal thing that is related to the air flow on your car...it's not like a radiator cooler....the airflow under the car is so different between cars that it is mostly unpredictable. From what I found, you need to experiment with a transmission temperature gauge installed. I highly recommend the synthetic fluid...costly but apparently effective.

By the way, the trans pan with the little tubes or fins works at speed when there is air going thru the tubes but at slow speeds, there is not enough air mass being presented for it to do much

mike in tucson

Consistent temperatures above 175% will shorten the life of your 700R4

Check this link.

The greatest chance of higher temp is running in higher (3 & 4) gear unlocked. Certainly, do not drive for any distance in 4th without lockup.

Invest in a lock-up switch so you can lock up the trans in any gear, and make sure that the brake pedal will disengage the lockup.

Its virtually impossible to overcool an autobox, As said over 175 won't do it any good.
Trans cooler is a must have, In my opinion a stand alone decent stacked plate type is the best. I never use the in rad type.