Corvair Forum

I've drained the differential and refilled, but the transmission is a problem. I'm using a suction gun with a 1/2" ID tube. In the tight space, I can't get in a position to have the tube to go into the trans on an angle. It just goes in straight and sucks air, no gear oil. I'm going to try again using a smaller diameter tube.

I'm just wondering what other people use to do this.

I had the same problem trying to drain (suction with 1/2" tube) the oil from my 66 Corsa 4 speed transmission.

Just to clarify, on the LMs the (4 spd) transmission and differential share oil -- and both have fill plugs but no drain plugs. Correct?

Steve
66 Corsa
Ofallon, MO

illinicorsa wrote:Tue Nov 07, 2017 8:41 am

Just to clarify, on the LMs the (4 spd) transmission and differential share oil -- and both have fill plugs but no drain plugs. Correct?

And you are using GL-4 gear lube to fill your transaxle, right? NOT GL-5!

MT-90 75W90 GL-4 GEAR OIL


AMSOIL Manual Transmission & Transaxle Gear Lube 75W-90

To correct an error in Bodie's post -- DO NOT USE Redline MT-90 in a Corvair transaxle. Redline's site specifically states that MT-90 is NOT approved for hypoid gears (differential). So it is NOT acceptable for use in a Corvair transaxle since protection for the ring and pinion differential gears is inadequate. Redline does make a modified GL-5 lube that is suppose to work with brass synchronizers called - 75W90 NS GL-5 and states it's approved for transaxles with brass parts. NOTE: Redline NS GL-5 is different vs. their GL-5 which is NOT approved for transaxle use.

I did not know that about their gear lube products. The bottle lable states that it is suitable for transaxles, but the website states otherwise!

https://www.redlineoil.com/mt-90-75w90-gl-4-gear-oil

Red Line wrote:Since most GL-5 gear oils for differentials are too slippery for manual transmissions, Red Line offers these products that ensure proper shifting while providing ultimate wear protection

Appropriate coefficient of friction for most manual transmission synchronizers (other's synthetic gear oils are often too slippery for proper synchro engagement)
Red Line offers lubricants to pinpoint nearly every transmission application
MTL, MT-85 & MT-90 are not for use in differentials with hypoid gears
Excellent gear and synchro protection, balanced slipperiness for easier shifting in cold climates
Excellent for high- and low-mile transmissions
Compatible with petroleums and other synthetics

There is a lot of contradictory information on the Internet about which gear oil to use for older cars.

I've contacted AMSOIL about using their GL-4 Transmission & Transaxle gear lube for hypoid gears. They told me for hypoid gears I need to use their GL-5 Severe Gear 75W-90 lube. It's hard to believe that our old transaxles need newer generation GL-5 gear lube. I'm confused because Clark's sells and recommends AMSOIL GL-4 for standard transmissions/differentials. Also, my understanding is that GL-5 is not safe for the yellow metal synchronizers in our transmissions.



If our manual transmissions and differentials share fluid, what are we supposed to do?

Bodie said : I did not know that about their gear lube products. The bottle (Redline MT90) label states that it is suitable for transaxles, but the website states otherwise!

The problem (as with many "boutique" lubricants on the market) is the point of reference. There ARE FWD transaxles that do NOT use hypoid gears and in that case the MT-90 is fine, BUT the Corvair transaxle uses a standard transmission driving a conventional hypoid gear differential in one case sharing lubricant - also a common configuration in many mid engine Italian exotics from the 60's and 70's

Many modern FWD transaxles now use ATF (Automatic trans fluid) to lubricate the entire transaxle assembly.

Wagon Master wrote: ↑Thu Nov 09, 2017 7:59 am Sorry but my suggestion would be to find a bottle of the manual transmission and transaxle lube at a parts store and read the label. Since obviously the representative you spoke to at Amsoil can't.

Yes, I would read the label but I can't find AMSOIL, locally. I can get Sta-Lube multi-purpose hypoid lube, locally. It's conventional oil, not synthetic, but safe for 'yellow metal' synchronizers.