jeepmedic46
Expedition Leader
Going to be changing my Transmission and transfer case fluids and differential fluids. Should I use synthetic fluid? I have over a 113000 miles and the fluid has never been changed.
Fluid change
- Thread starter jeepmedic46
- Start date
getlost4x4
Expedition Leader
my commander runs synthetic in all the fluids. its only a few dollars more and worth it in the long run.
jeepmedic46
Expedition Leader
Synthetic fluid will be ok even though the fluids haven't been changed in a while?
ExpoMike
Well-known member
Actually I have heard positive and negatives about switching over to synthetics on high mileage transmissions. The debate goes as follows,
High mileage trannys typically have worn some of the clutch material away but is still "floating" around as particles which has a little "bite" to the fluid. This helps to keep the clutches from slipping even though they have worn some.
Many have noted that within a 1000 miles of changing a high mileage tranny over to synthetic fluid, they start having major slippage problems which a lot of times resulted in a tranny repair/replacement. This was caused because the new fluid is much more slippery and without the extra floating clutch particles helping with the friction in the clutch packs, it causes them to burn up.
Others with high mileage have kept with the OEM recommended fluid and have not found any long term problems as a result. Since it doesn't have the same slickness as synthetics it tended to not cause problem. This also is done as a simple fluid drain and replace, NOT a fluid flush. Those who did a fluid flush (where all the old fluid is flushed out of the converter as well), they would run into the same problem as going to synthetic. The converter typically holds about a quart or more and keeps some of the clutch particles to mix in with the new fluid.
Personally I have never switched over to synthetic fluid in trannys/transfer cases (since my 231 case uses tranny fluid), using what was recommended by the manufacturer originally.
My opinion, YMMV.
High mileage trannys typically have worn some of the clutch material away but is still "floating" around as particles which has a little "bite" to the fluid. This helps to keep the clutches from slipping even though they have worn some.
Many have noted that within a 1000 miles of changing a high mileage tranny over to synthetic fluid, they start having major slippage problems which a lot of times resulted in a tranny repair/replacement. This was caused because the new fluid is much more slippery and without the extra floating clutch particles helping with the friction in the clutch packs, it causes them to burn up.
Others with high mileage have kept with the OEM recommended fluid and have not found any long term problems as a result. Since it doesn't have the same slickness as synthetics it tended to not cause problem. This also is done as a simple fluid drain and replace, NOT a fluid flush. Those who did a fluid flush (where all the old fluid is flushed out of the converter as well), they would run into the same problem as going to synthetic. The converter typically holds about a quart or more and keeps some of the clutch particles to mix in with the new fluid.
Personally I have never switched over to synthetic fluid in trannys/transfer cases (since my 231 case uses tranny fluid), using what was recommended by the manufacturer originally.
My opinion, YMMV.
jeepmedic46
Expedition Leader
Where I haven't changed the fluid I was just going to drop the pan and not flush the system. You are right it might be a bad idea to put the synthetic fluid in the tranny with the high mileage.