Have the six speed tranni in my truck. Years ago for the tranni oil change I tried the Royal Purple oil and the difference compared to the OEM oil was barely noticeable. Then I switched to Pennzoil Synchromesh and again, no real difference. Have been reading that quite a few guys have tried Amsoil and noticed that the tranni changed smoother.

Need some honest opinions on what is the best oil for my transmission for smoother gear changes. In reality, is one brand REALLY any better than the other for smooth changes and a longer lasting transmission?

Did a search here and on the 'net and did not discover anything conclusive, so thought to throw my questions to you more knowledgeable gear heads.

 

Mine has had nothing but Amsoil from the first service, can't remember if there was a difference from what was in it from Factory. I am partial to Amsoil and would not change. Have you considered new hydros for your clutch? They may be weak.

 

What do you mean by new hydros? The 'feel' of my tranni has not changed from new.

 

i think he's talking about hydraulics (master cyl, slave cyl) hydraulics don't get weak! they either work or they don't.... if they don't, leaking would be the problem!
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Ha! I know all about the master/slave cylinder problems. A few years ago was on a trip and had just unhooked my RV. Was at a light waiting for it to change, in gear and clutch in. Suddenly the truck took off against the red light, even although the clutch was on the floor. Talk about rapid pushing on the brake pedal and reaching for the key!!! There was no leaking oil, so it was an internal failure. The local Dodge dealer was not far away, so drove it there with no clutch.

There is nothing wrong with my clutch or the tranni. All I am looking for is oil info as I need to top up the tranni after an oil leak, so was considering doing an oil change and going to another brand just for kicks.

 

iv'e been using Pennzoil with good results. but then i don't "abuse" my truck

Synchromesh Manual Transmission Fluid | United States

 

That is the oil that has been in my truck for ages. I do not abuse my truck either. It sometimes gets worked hard, (isn't that what a Cummins likes?) but not abused

 

I've been running Amsoil synchromesh in my 6sp. There was a long thread on one of the forums (maybe this one) on 6sp lube. The writer was using a 50/50 mix of Amsoil synchromesh and Amsoil manual trans fluid. One of the transmission rebuild shops was using a mix of synchromesh and Delvac 50. Which would come out to about the same as mixing the two Amsoils. I think they were supposed to run cooler with that mix. IIRC it was Allstate Gear. They may have a writeup on their website.