i changed all the gear oil in the whole truck, now i have to shift even slower to keep the gears from grinding, and its next to impossable to shift into second when its cold. also downshifting to 3rd is also more difficult. shifting into reverse is butter smooth now, but i'd gladly give that up to be able to shift into 2nd and 3rd efficiently. i used 80-90 wieght.... is there a better weight that will improve my shifting?

Al

 

Hey I had the same problem with my truck! Running the same oil! And yes you can go down in weight of oil! This might sound weird but my dad has ran Automatic transmission fluid in his stick shift truck before! I can call him and ask him about what he would suggest as far as oil! He owns a transmission shop and has been doing it for 30 years! Sorry i couldent help more.

 

So what Grade oil did you use, GL-4 or GL-5? Gear oil has a grade and a weight. I like Redline MT90 GL-4 gear oil:
- http://www.4crawler.com/4x4/index.sh...ntheticGearOil

GL-5 oil is too slippery for the synchros to work well.

 

Yeah redline is good stuff, but it'll run ya some serious cash. I think I paid $10/qt or close to it.

 

Not all that bad in the long run. Sure, it runs $8-9/qt, but regular gear oil is probably like $5-6 nowadays (haven't bought any for many years) and with needing 3-4 qts. the cost difference is only $10-15. I find the Redline oil lasts almost forever, I never routinely change mine since I seem to have some reason to get into the tranny or t-case or diffs every 5-7 years or so. I'll drain and change it then, but if I can save the hassle of even one gear oil change, that makes up for the price difference. And if you find a local shop that carries it, you might get a case discount. I got a case at a local racing shop that sold Redline.

Now if you run a lot of mud and deep water, may as well get the cheapest gear oil you can and plan on changing it a lot.

 

you nailed that one on the head.... i used GL-5. i'll grab some GL-4 and swap that out this weekend. thanks!

Al

 

Still seems strange to me that GL-5 would cause those problems. That is what's recommended for our transmissions. I'd be real interested to see if that fixes it, if so that's what I'll be running.

The Marlin Crawler site says to run nothing (not even synthetic) but GL-5 in a newly rebuilt tranny for the first 10,000 miles, because the syncros won't break in properly otherwise. Maybe it's a totally different deal once it's broken in??

 

that does seem odd, and i was surprised my parts guy would have got it wrong (yeah, he's that good)... but i guess he didn't?

either way, i'll get it changed out to GL-4 and report back my results.

Al

 

My '85 owners manual says GL-4 or GL-5:
http://www.4crawler.com/4x4/4R_TechInfo.shtml#Fluids

GL-4 is made for synchromesh transmissions, GL-5 as EP additives to make it slipprier for use with helical gears like you find in the axles. GL-5 won't hurt the transmission, but it is not the optimal lube for it either. I can feel the difference between GL-5 and GL-4 in my 5-speed. With GL-5, shifting is more sluggish. And yes, I usually run the lowest cost GL-5 oil I can find for break-in and change it after 500-1000 miles or so.

 

Huh. Good to know.

 

i know some guys running the SM465 will use 50w motor oil instead of GL-5 for faster shifting.

Al