Manual Transmission Fluid

[fortop]

I need to change the fluid in my 4 speed manual transmission - 1983 C20 regular cab long bed Chevy. At least I think it is a 4 speed - it has L -1-2-3 and reverse on the shift knob. I have read both 80-90 gear lube and Dexron II is the proper fluid - 8 pints total. Does anybody know what the correct fluid really is? Also, does it make a difference which brand I use?

Thanks.

[boflaade]

I don't know why you need to change the oil but Dextron is for automatics. 60W should do and I found the GM dealer has an oil called "Syncro" cheaper then the local parts store. Yes that transmission is a four speed even though the lowest gear is rarely needed.

[fortop]

I thought Dexron was just for automatics also, but a mechanic acquaintance of mine told me Dexron was the fluid to use for a 4 speed, and here is something I found in Chilton's:

 

1982-85

 

On all manual transmissions except the 4 speed with overdrive, use SAE 80W-90 GL-5 gear lubricant or SAE 80W GL-5 in colder climates.

On the 4 speed manual transmission with overdrive, use DEXRON®II

 

I bought this 83 used about two years ago. I think the fluid has never been changed, and the fluid level seems to be low. So, I thought I might as well change the fluid.

 

I'll check with the local dealer, although my experience is that they are usually not very knowledgeable in these matters.

 

Thanks

[jelisfc]

If you have granny low you are right in using 80-90W gear lube. You'll have the SM465. Short cast iron last forever version.

[fortop]

The local dealer parts department recommended regular 80-90 gear lube. I bought a gallon of cheap AutoZone 80-90 and a suction tube for about $11. This is an old beater truck. I decided to top off the transmission instead of changing the oil, since it was only about 1 1/2 pints low. It shifts much better now, especially going into reverse. The transmission leaks but apparently not bad enough to lose a lot of fluid. I will just check it periodically for now. Thanks for the info.