GL-4 gear oil: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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Jan. 15, 2012 2:25 p.m. nicksta43 Reader

I finally found a 17mm allen wrench that wasn't part of a high dollar set. So I decided to change my trans fluid. The car calls for a SAE 80 oil GL-4. I did a little research and the GL-4 is an old standard that was replaced with GL-5. However there is a a component in the GL-5 oils that has about twice the sulfur of GL-4 and has been known to eat away at the soft yellow metals in the trans i.e. brass synchro's. It is my understanding that this package in the GL-5 is the main difference between it and a GL-4.

I really wanted to run Redline oil because I have heard nothing but excellent things about it and it is one of the few gear oils left that is rated GL-4. However I am too impatient to order it and wanted to get this done today so I went out looking for something that would work locally. I was going to pop for the $20 per qt. Royal Purple that is rated both GL-4 and GL-5. They only had one qt. and I needed two so I went ahead and got the Lucas oil synthetic 75w90 that has both ratings.

First of all I have to say this fluid made a HUGE difference in the shifts. No more crunching in first and second. Third, fourth and fifth slide in like butter.

My concern is because it's rated GL-5 I'm going to be destroying my synchro's. But I feel I should be O.K. because it has the GL-4 rating as well. Should I just go ahead and order the Redline and plan on replacing the Lucas with it?
Jan. 15, 2012 2:54 p.m. SkinnyG HalfDork

I've never found an off-the-shelf GL4-only lube locally. I have run a GL4/GL5 lube with no problems for ~years~. I ~did~ have issues with straight GL5.
Jan. 15, 2012 2:58 p.m. nicksta43 Reader

I found a GL-4 but it was 140w. Good to know you've had success. Maybe I'm just being paranoid.
Jan. 15, 2012 3:06 p.m. Streetwiseguy SuperDork

I've encountered, rarely, situations where oil that is too slick or heavy won't let the blocker rings grab properly, causing crunchy shifts.

I've actually "fixed" synchros in my junk by running ATF in standard transmissions that were designed for gear oil. I dunno if I'd ever do it in anything I was driving in anger, but I had a Commanche pickup that I drove for 7-8 years with the wrong oil in it. It was still shifting fine when the floor fell out... well, actually, the floor had fallen out quite a while before, but eventually the carpet split, and...
Jan. 15, 2012 5:51 p.m. driver109x HalfDork

Sta-lube still makes 90wt and 140wt gl4 gear oil. My local Napa and Carquest still carries them.
Jan. 15, 2012 6:41 p.m. jimbbski Reader

Most manual trans will run on ATF.

The early T5 used gear lube. Later models of those trans that were rated as "World Class" got ATF while the plane jane still used gear lube. The two major differences between the two trans were the WC gears on the main shaft ran on roller bearings instead of the shaft itself and used a clutch type materal on the syncros to improve shifting. It was this clutch materal that really required the ATF in the trans as gear lube caused problems with this materal.
Jan. 15, 2012 7:18 p.m. 11110000 Reader

Volvo's manual transmissions from that era called for Type-F ATF. I've used Redline Racing ATF with great success in my boxes.
Jan. 15, 2012 7:40 p.m. nicksta43 Reader

I gave some thought to using atf, the manual even says in colder climates it's ok to use a hd engine oil. It feels real good with the Lucas in it I think I'm just going to stick with that.
Jan. 15, 2012 9:47 p.m. Spitsix Reader

+1 for NAPA
Jan. 15, 2012 10:24 p.m. porksboy SuperDork

Well here's a question. What should I put in the box of my 90 CRX? I do get the occasional crunch on 1-2 up shifts. It only happens when I am flogging it, if I take my time it is ok. 3-4 is stif at times too. It is the original box and everything is stock except for a K&N and an exhaust system running a magnaflow.