Mixing synthetic with conventional

schroederMP · 01-27-2012, 05:23 AM

I about to change my tranny fluid. My tranny was built by the previous owner...and I'm unsure what the shop put in it as far a tranny fluid (they have failed to call me back)

My question is... lets say they put conventional tranny fluid in it, then I put synthetic fluid in it when I change it. Will that hurt anything?

I'm not flushing, just changing the gov selinoid and filter.

Dont wanna fry my tranny...do expensive to do guess work.

I tried searching and failed

Thanks

TRig · 01-27-2012, 05:52 AM

You'll be fine. Every synthetic oil I've used is compatible with conventional oils. On the tranny, you're not going to get all of the oil out unless you performed a true flush.

schroederMP · 01-27-2012, 05:57 AM

Awesome...thank you for the quick reply!

***rufushusky*** · 01-30-2012, 06:59 PM

Quote:

Originally Posted by schroederMP

I about to change my tranny fluid. My tranny was built by the previous owner...and I'm unsure what the shop put in it as far a tranny fluid (they have failed to call me back)

My question is... lets say they put conventional tranny fluid in it, then I put synthetic fluid in it when I change it. Will that hurt anything?

I'm not flushing, just changing the gov selinoid and filter.

Dont wanna fry my tranny...do expensive to do guess work.

I tried searching and failed

Thanks

Factory spec for the 48re is ATF+4 which is a synthetic fluid to begin with...

**Duluth Diesel** · 01-30-2012, 08:26 PM

You'll be fine, synthetics are compatible with conventional oils. ATF+4 from most manufacturers is a Group III mineral oil based synthetic. AMSOIL ATF is a Group IV. The Group IV synthetic is more thermally stable and will protect a hot transmission better, but even Group IV AMSOIL can be mixed with the lower grade Group III products.

-Chuck