Best choice for T14/D20 lube?

I know my FSM recommends 80W GL-4

It seems that straight GL4 lube is rare these days and most is GL-5 with only a few that say GL-4/GL-5

After searching extensively, there is lots of controversy over using something GL-5 compatible where GL-4 is recommended.
Most of the talk is about newer 4spd and 5spd boxes.

I've found this at my local NAPA and is my frontrunner as its purely GL-4.
http://www.napaonline.com/Search/Detail.aspx?R=SLRSL24239_0006410049

I was wondering what the hive has been running successfully?

 

regler ol 80 W 90 from autozone....

 

GL-4 is available, and IMHO its worth it.

 

i research my butt off on this for my T150 and D20,, now i am using 50W motor oil, but dont listen to me, my tranny is still screwed up after a rebuild, wont stay in 2nd gear

 

I've also heard of good results with 50w.

 

There certainly is a lot of information out there. I think most of it has to to do with GL5 additives having too much erosion impact on the synchronizer rings...assuming they are of a yellow metal, which most are in these Jeeps.

Most everything I've read says to use GL4...in the 80w-90 variety. Since that's what the Jeep manual states, I'm thinking that's what I am sticking with.

This is an informative link to a PDF file discussing these issues...although he does focus on the impact to Corvair transmissions the information is valid for any manual transmission.

http://www.widman.biz/uploads/Transaxle_oil.pdf

 

I wished i could get back all my sources, i lost everything due to a hard drive issue, and that WAS my back up,, anyway, most would be correct to say GL4 is the lube to use. What people are neglecting to realize is that 80/90 gear lube in 1975 era is NOT the same as GL4 in todays era. From my research I found that 50W motor oil is the equevlant. One note is that a single weight motor oil is Non detergant and does not have all the slippery additives and conventional oils or multi weight oils. If you do happen to find GL4 make sure its not rated for anything other then GL4. I am in Mexico and went to the Jeep dealer to find some, 40 bucks a quart is what they wanted and it was still wrong, it was labled GL4/GL5 ..i ended up finding some at a tractor supply place. I used it for 6 months and the tranny was noisy, with the 50W I have ZERO noise. Anyway, thats all I have for input, if were me, 50W, but for you, its your call, both 50W and GL4 are fine.
Good luck on the decision.. (I hate doing that)