The Money Pit

The stuff costs a small fortune from what I remember.Anyone here used it that can say for sure the benifits of synthetic over the usual DextronIII automatic tranny fluid?

munday

Well synthetic is more slippery than regular, now combine that with clutches........

I would only use synthetic in something that asks for it like my richmond 6 speed. I wouldn't use it in a rear end either, but that's just me.


[Modified by munday, 12:56 AM 8/4/2003]

BSeery

I would never put it into a used tranny. It will clean the deposits off the clutches - aka remove the friction points.

Those are usually good for firmer shifts, just like running ford fluid or the B&M stuff.

I would never put it into my car. I will use what GM says to use. Kind of my theory for rear end lube too.

rhoeven

Enemy #1 for automatic transmissions is oil temperature.
Synthetic oils brake down at way higher temperatures compared to standard ATF oil.
Same for differential oil. The only thing to watch out for is that some synthetic differential oils do not contain limited slip additive. In this case the GM additive is required.
I run Redline D4ATF in my 700R4 and Redline 75W90 in the differential. The latter has limited slip additive included. Others like Amsoil do too.
No problems at all. No leaks.
Synthetic oils might be a little more expensive, but they also don't require to be changed that often.
My engine gets Amsoil 10W40. The engine had a small leak before but it did not get worse after the switch to synthetic. Fact is that synthetic oils last longer and lubricate better. This means longer lifetime for the car components.

Roger

munday

Synthetics do lubricate better, they just lubricate too good for anything with clutches, and AMSoil is some good stuff. I've used it before.

flynhi

As mentioned above, high temp is the enemy of transmissions since it accelerates the breakdown of fluids ability to lubricate. I recently cooked a 700R4 in my Suburban due to getting stuck in traffic in Phoenix while my rear view mirror thermometer read 134*. The fluid turned black and smelled like it was burnt when we drained it. The rebuild shop told me that my trans probably would have survived if I had been using synthetic fluid rather than conventional. Synthetic fluid is expensive but cheap compared to the cost of a rebuild.
Probably not as important in 4 speeds or diffs since temps don't get that high unless you are racing.