About 2 years ago I rebuilt my 700R4 automatic trans in my '88 Chevy
blazer s-10 4x4. As I was completing the job, my brother mentioned to me
that I should put Mobile1 ATF in. Unfortunately he had meant natural Mobile1
whereas I bought synthetic. Obviously synth. is much more expensive and not
what my 700R4 was really designed to be using. The big question is, can I
switch back? If so, is there anything that I need to do other than dropping
the pan, draining and a new gasket?
There is no problems and only benefits to running synthetic in the 700!
If you really don't want to put synthetic in when you do filter changes or
when it gets flushed, then don't. There is nothing special that needs to be
done. Synthetics and petrol based ATF are fully compatible with each other.
Synthetic is much cleaner and will be much better for your trans in the
short AND long term, but its your Truck, your call.
The better the trans fluid that you run the farther ahead you will be. I
don't know off hand of and ATF blends. If you have synthetic in it, my best
suggestion is to run it! It will cost more in the short term but will pay
big in the long term and even help with shift quality and cool running for
the life of the trans.
Are you due for a filter and flush? Is that why your talking about
"Shades" <shades_1970(at)netins(dot)net> wrote in message
Well cost wasn't really my concern. I thought that I would be better to run
natural in the 700r4. It would probably cost me $36 for natural, and $60 for
synth -- I can afford the $30.
The first reason why I considered switching back was if it were doing harm
or being less effective in the 700r4. The second reason is that I noticed
that at high RPMs on the highway it will run at (for example) 3500 rpm.
After 10 seconds, the rpms drop down by 400-500 rpm and you feel the truck
pick up a little bit -- like the trans just clamped down a bit harder on the
clutch plates. I thought that the synth was too thin and that it was taking
longer to build up pressure on those plates. There is a small drip coming
from where the control level runs in through the case -- nothing so much
that there is ever a spot on the ground, but enough that I notice it's a
little wet around there. That may -- over time cause my trans level to be
low. I'll check it again tomorrow and see if that's the case.
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