The problem with the NV4500 is it needs a high-heat resistant, high-film-strength (heavier) synchromesh-type fluid to keep the carbon fiber syncros happy. Syntorq LT is the only lubricant on the market that was tested and approved, actually specifically developed, for the NV4500. Some of the others listed for that grade/weight (Redline, RP, etc.) may be compatible, based on the manufacturer's specs/claims.

It's your tranny.

 

Whoops, I thought they used the same fluid.

 

Thats true - but the 6 speed is also quite picky about what fluid you put in it. I hate to sound like an AMSOIL advertisement because I hate the way they market and sell the stuff but they have everything you need. "One stop shopping" so to speak. and they have the "correct" fluids that arent going to cause damage to your truck. And yes, incorrect oils can cause damage.

 

Not hijacking the thread, but I just tried Royal Purple because they seem to have good products, and it was readily available at the local parts store. I would have to order amsoil and i hate waiting for stuff when I want to get it done. It really does shift smoother over the stock fluid, and I added an extra quart through the shifter hole, so it should be good until next time. I'll probably try amsoil next change.

 

Im not really knocking RP...but making the point that fluid matters make sure you use the right stuff. I put Redline MTL, which is an excellent fluid in my 6 speed. I immediately developed a slight grind going into third gear. Right away I thought I needed to do an $ tear down. After talking to a couple of people, I dumped the redline and put the correct amsoil in and the grind went away immediately. Turns out the Redline wasnt the correct weight.\

That being said, the whole issue with using the correct oil in the NV-4500 is that if you dont the oil will damage the carbon fibre synchros.

 

According to the spec, that Redline MTL would proabably work good in the NV4500. Too thick for the G56 or NV5600, tho - that's why it started grinding.

 

yup. And just my personal experience here

 

Wow, thanks for all the feedback. I haven't been able to get on in a few days and I was surprised. I'm thinking about going with the amsoil, seems from my research it'll be what's best. And yeah currently 3rd is scratching, but not bad and if I just truck along like a normal person, I can keep it from scratching. It's in need of a rebuild so I'm just making it last.

 

I know im in the wrong spot here but sense your on the topic is mobile 30 wt. The right oil for the getrag?

 

That was the correct answer 20 years ago. Today the correct answer is synchromesh. The lighter version(s).