1995 850, 180,000 miles. Trans shifts fine unless it is hot. Cool weather no issues but when it gets warm outdoors I get clunk when it downshifts, like appraching a stop. Does not happen every time. After it does the clunk it kind of slips when starting out for a second or two. It moves but not much, then it "catches".

So, transmission has a problem when hot. Been doing this about 20K miles. I change the fluid about every 5-10K using bay 13 flush method. This helps but does not fix. First few times I used synthetic fluid but last time decided I wasn't getting much benefit from $100+ cost since I dump it often.

Wondering if it is worth putting on a transmission cooler. Thinking is it makes the tranny work 50 degrees cooler then it ought to work at 100 degrees as it does not at 50. I made up the 50 degree drop but you get the idea.

Opinions, success stories, disaster stories?

Thanks,

Terry

'95's are noted for doing this. Mine's had the same problem for the past 40K miles and it's gradually getting worse. My car currently has 135K miles. I believe it was started by the PO letting his teenage son drive the car and he probably spent way too much time flooring it in the "sport" mod. I didn't detect it when buying the car because I didn't do a very thorough test drive. At that time it would only show up after a fast drive down the freeway. I put a cooler on it a few years ago and switched to synthetic because regular tranny fluid would burn after about 8 K miles. Now,of course, it happens almost all the time during the warmer summer months even just driving around town. So, yes, a Hayden cooler will help and slow down whatever problem is developing in the tranny. Though I would still recommend switching back to synthetic fluid.

Before adding an additional cooler, you might want to buy a cheap lazer light thermometer and check the temp of the fluid in the top line going to the radiator. Then compare the bottom line temperature.

It just might be that you need to 'power wash' the radiator and clean out the dirt between the fins. Good idea to do that anyway.

Klaus
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Always willing to listen, just not able to take direction.

Power wash radiator: sounds like it can't hurt. Do I need to remove the radiator or can I blast it with a power washer in place? Minor concern about shooting water into engine bay but I guess it happens when it rains.

Really wondering if I have to remove the radiator and spray from inside out to push stuff back where it came from rather than trying to push it all the way out the back.

Regarding measuring temperature drop across radiator: cool idea. I'll go get one of those IR temp things. Any idea what a reasonable tranny fluid temperature drop through the radiator would be?

The engine fan is easy to remove for reverse power washing, do not remove the radiator just to clean the fins.

There should be a 20F drop if you are lucky and the engine fan is running. The AC condenser will add heat to the radiator. Make sure you have enough ATF, the dipstick should read at least full on the hot side with the engine running and the fluid hot. I can be higher than "full" at very high temps.

Adding an additional oil cooler to the front of the condenser is a pain, especially in northern climates where it would have to be removed for winter temps.

Klaus
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Always willing to listen, just not able to take direction.

What does the fluid look like when you change it? How old is your radiator?

cooler might help, so might using thicker oil next time.
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If you're not driving it "like its stolen," are you really driving?

Original radiator. Fluid is deeper red but not burnt brown when I change it.

Last change was only a couple thousand miles ago the fluid still looks new.

The last time I changed the fluid I put in regular instead of synthetic because I tried some "SeaFoam" trans cleaner and was using the regular fluid to wash that out. So I think my plan was (is) to wash out the tranny with cheap stuff and go back to synthetic next time.

Did not know there was a thicker oil... What is it? I thought there was just ATF and that was it: no selection like there is with motor oil.

Since its the original radiator, powerwash it (and the condenser) first, and see if anything improves. 14+ years is a lot of time for crap to get into the fins and restrict airflow.

There is manual fluid, you can find some syncromesh fluid at autozone with kinematic viscosities about 9.5. Your ATF (when hot) will be about 7.5. If you've just got an older transmission that is worn enough that it needs slightly thicker oil I'd go this way before I tried a transmission cooler. Clean out the fins first, if that doesn't work try a bottle or two of syncromesh fluid. If that still isn't working, I'd probably try a new (read:junkyard) radiator then as a last resort the tranny cooler (also junkyard if you can find one).

How's your coolant temp btw, it should also be hot if your radiator is clogged? Don't trust the gauge, if you don't have your own OBD scanner and you've got a laptop try something like this .


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If you're not driving it "like its stolen," are you really driving?