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Temperature - Transmission, Oil, and Water

Zixxer

Well-known member
Joined
Dec 30, 2003
Messages
191
Location
Stafford, Virginia
Corvette
1982 Red Coupe
I hate to ask what has been probably answered a dozen times but all of the searches I've looked at have lots of different answers so here goes.

I have a 96 LT1, stock, no mods, newly rebuilt transmission, recent oil change (Mobil 1), and replaced optispark and water pump by the previous owner approximately six months ago. Based upon the optispark change I assumed some change of coolant (Dextron II). The car runs great so maybe this is a silly question but I've just never owned a car that seems to vary so greatly in temps.

Oil: 195-220 usually holds with 5 or 10 degrees of water temp.

Water: 190-230 the 230 holds in town and drops back with A/C and fans going but I never see 180s like a lot of folks mention unless it's a quick trip. I'm fine on the highway with the temp steady at 195-197.

Automatic Transmission: - here is my big concern; 185 to 230. I'm always in the 200 range and I get concerned that in town driving hovers in the 220 to 230 range consistently. Everything I read about ATF fluid says that's bad but a few posts on this forum say it's normal. I can stay at 190 - 207 degrees cruising at 70ish but I notice it takes a long time for the temperature to start dropping back down.

I would be interested in everyone's actually temperatures just to see if I'm in or out of the ballpark. Average temperature outside is 85 to 95 degrees.

My next project appears to be flushing the coolant but I want to be sure I'm not wasting my time. Thanks Rick
 
Sounds like your AT fluid temp is just following the coolant temp. It's true that AT life is longer at lower fluid temps. You can always put in a cooler for it. I've been using Mobil 1 synthetic ATF for a while and it cured a high speed shudder on downshifting. I assume it will last longer at high temps too.

If you're worried about the coolant, can you test it? pH test strips, voltage between coolant and ground, etc. I've got the green stuff, not sure if it applies to your orange stuff.
 
Your water and oil temps are very normal readings. My 92 runs in those same ranges. You probably won't see coolant temps in the 180 range unless you have a 180 stat installed. Even then if the outside air temps are high, or you are in heavy city-type traffic, the temps will climb reagardless of the thermostat opening temps.

Unless you feel you need to do a coolant change, the Dex-Cool (orange) coolant really only needs to be clear and the system full. You can have a shop check pH and the temperature protection level. Doing a flush and refill on these cars is not a real simple task but doable at home. The best thing to have in your tool box is a factory GM Service Manual. You can get them from Helm at their website www.helminc.com or you can try eBay for used sets.

The LT1 motor should handle oil temps up into the 230-240 range with Mobil-1. I see 240 temps at open track days and it's never hurt anything.

If you suspect tranny temps being too high, you might talk with a reputable tranmission repair shop. Going to Mobil-1 synthetic ATF is a good choice and if the tranny has never been serviced, it might be worth doing a flush and a new filter.
 
Thanks

What is your automatic transmission temp on the highway and in the city?
 
The trans fluid temp on my 95 stays between 190 and 210.

I have the 160 therm, and manual fan switch. The coolent temp is usually about 100 degrees above outside air temp. (When its over 70 outside).

I posted some pictures on how to put in a switch for the cooling fans, the lower coolent temp also has an effect on the trans fluid temp.
 
Temps

My '95 LT-1 Auto is totally stock (but with rebuilt trans and freshly changed green engine antifreeze - it came with green being an early '95) and gets the same temp's that you listed. Conditions determine upper temp until the fans cut in at about 210 and 227, the thermostat controls the steady state lower temperature, 190+ with the stock t'stat.
 
Those temperature ranges are normal. GM did make them that hot to pass emissions.

If you want to lower those temps, try some Water Wetter in the coolant and a reprogram for the fans to come on earlier. I think it's LT1 Edit that you guys use. :w
 
Zixxer said:
Thanks

What is your automatic transmission temp on the highway and in the city?
I have no way of knowing as the 92-94 cars did not have a tranny temp readout. I had a AT flush done a couple years ago right before a track day and the original fluid that came out was still nice and clear with red color.

One thing that you may experience if you do an ATF flush (a complete change of fluid not just the ATF in the pan) is the shifts may be somewhat softer. The guy at the shop told me when I had mine done, that new fluid will sort of rinse off the bands making them smoother. After a couple of months, the original shift firmness seemed to come back.
 

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