four speed oil

[raj]

  What oil do i use in my 4 speed my service manual says use transmission fluid,
   but when i pull the trany out it was filled with 90 weight. is the 90 for an old used trany or did some one screw up. can i run synthetic oil i the 833 4 speed. do i need an additive similar to the rear end Thanks

[74 340 4speed]

I put a conventional 80w90 gear oil in mine.  I don't see any need for synthetic or an additive.

[AMXguy]

I run Mobil 1 75-90 synthetic in mine, we started using it in our Borg T-10's a few years ago guys swear by it. many say you can actually hear the difference in the noise level, it seems to me you can, I don't know but it's good stuff.

[Chryco Psycho]

I prefer synthectic as well but it has to be a GL4 rated oil , Redline Amsoil & GM syncro mesh are designed to work correctly in std trannys , I would use 80-90w if not using synthetic

[FY1443433]

I am no expert but BG has some great stuff on the market

www.bgprod.com

For all intended purposes, synthectic will run cooler then standard gear lube oil.  It does have it's advantages.

FY1

[AMXguy]

 This got me thinking so I cheked it out, Mobile 1 synthetic is GL-5 rated which is the new higher standard replacing GL-4.

[oldkimmer]

The 833 was never designed for synthetic oils....kim.......

[Chryco Psycho]

No kidding seeing as the trans was designed 30 year before synthetic oil , but that doesn't mean syn oil will not owrk if it iis the right type , GL5 is too slippery for the syncros