Correct transaxle fluid?

[scooper]

I'm having a problem with the posi clutches in my 66 Corsa trans axle, they are chattering/grabbing when turning. I'm going to drain the fluid, put in some of the GM posi additive, but what do I put in for fluid, 85w-90?

[joelsplace]

Yes but you want GL4 or something that specifically says it's ok for your transmission's brass blocker rings. Most GL5 oils will eat the brass over time.

[66vairguy]

Oh now you've done it -- LOL. No end to suggested fixes for this problem.

First - a manual transaxle must use GL-4 NOT the common GL-5 or GL-4/5. GL-5 causes issues with the transmission synchros.
Second - Once the clutch packs start to complain you need a lot of POSI additive with new lube to clean them up and this can cause the transmission synchros to not work well. WHAT TO DO!. Contact Davemotohead on the corvaircenter forum. He has had success with a Ford additive. You can put extra in and do some low speed turns to work new lube into the posi plates and shift VERY carefully. Once the plates stop chattering and grabbing you drain the transaxle and put in new lube with a MODEST amount of additive. It's a PITA to do, but so is rebuilding a posi differential!!! Fortunately Seth Emerson on the corvaircenter forum just announced he is selling reproduction POSI clutch packs. NOS are scarce and $$$$$$.

Note that GM went back and forth about this -- some manuals say "USE GM POSI ADDITIVE" and others say "DO NOT USE POSI ADDITIVE" depending on the year of the shop manual. It comes down to keeping the clutches lubed vs. not allowing the transaxle lube to become too "slippery" with additive which inhibits the transmission synchronizers function. Bottom line - change the transaxle gear lube every 20K miles, that's what the old Vette guys learned to do and it solved their POSI issues. No amount of additive will work with worn out and dirty transaxle lube.

[jetcat]

Oh now you've done it -- LOL. No end to suggested fixes for this problem.

First - a manual transaxle must use GL-4 NOT the common GL-5 or GL-4/5. GL-5 causes issues with the transmission synchros.
Second - Once the clutch packs start to complain you need a lot of POSI additive with new lube to clean them up and this can cause the transmission synchros to not work well. WHAT TO DO!. Contact Davemotohead on the corvaircenter forum. He has had success with a Ford additive. You can put extra in and do some low speed turns to work new lube into the posi plates and shift VERY carefully. Once the plates stop chattering and grabbing you drain the transaxle and put in new lube with a MODEST amount of additive. It's a PITA to do, but so is rebuilding a posi differential!!! Fortunately Seth Emerson on the corvaircenter forum just announced he is selling reproduction POSI clutch packs. NOS are scarce and $$$$$$.

Note that GM went back and forth about this -- some manuals say "USE GM POSI ADDITIVE" and others say "DO NOT USE POSI ADDITIVE" depending on the year of the shop manual. It comes down to keeping the clutches lubed vs. not allowing the transaxle lube to become too "slippery" with additive which inhibits the transmission synchronizers function. Bottom line - change the transaxle gear lube every 20K miles, that's what the old Vette guys learned to do and it solved their POSI issues. No amount of additive will work with worn out and dirty transaxle lube.

Timely question for me as well...
Just finishing a rebuild on my 66 posi transaxle for my coupe. I bought the newly available posi plates from Performance Corvair. No idea what oil was used in it before but considering the condition it was in, I don't want to know. My experience with my non-posi transaxle in my 66 convertible has been very good. I changed to Amsoil GL4 synthetic oil a few months ago. Made a significant difference in the smoothness of the gear changes. Don't know what oil was in it previously.
Does anyone have experience with using a GL-4 synthetic with the posi? Should I try it first without the posi additive?
From my current research, lots of aftermarket posi diff manufacturers don't recommend synthetics for some reason.

Bob Wilcox
Paso Robles, CA

1966 Turbo Corsa Convertible
1966 140 Corsa Coupe

[66vairguy]

Bob - Yes synthetics seem to be an issue with POSI, although I don't know why. When I had a new 2000 Chevy Silverado truck I took it in for routine service and I was told my rear end lube would be changed at NO cost to a standard lubricant because there was an issue with the synthetic lube installed at the factory.

Just me, but I'm not a fan of Amsoil products because they don't publish technical data. Lots of hype, little in the way of facts. Richard 1 on the corvaircenter forum is a lubricant expert and he won't endorse any Amsoil products due to a lack of information.

Some of the Corvair folks that race use the Red Line products. They have a synthetic GL-5 modified for use in transaxles. I'm not endorsing the product, but so far folks claim Red Line 75W90 NS GL-5 works. NOTE -- Red Line has two other products that DO NOT work in a transaxle. One is MS 90 MT that states "Not for use in transaxles with hypoid gears" (The Corvair has a hypoid ring and pinion). They also sell 75W90 GL-5 that is NOT approved for use in transmissions. You have to use the product with "NS" in it that is modified to work with out issues with transmission "yellow metal" synchronizers like the type in a Corvair.

I'm not racing so I don't use synthetics. I just change the lube every 20K miles. Dan The Transmission Man in Los Angeles, CA put it this way "The major cause of Corvair transaxle failures is old dirty lubricant that has never been changed".

[jetcat]

Bob - Yes synthetics seem to be an issue with POSI, although I don't know why. When I had a new 2000 Chevy Silverado truck I took it in for routine service and I was told my rear end lube would be changed at NO cost to a standard lubricant because there was an issue with the synthetic lube installed at the factory.

Just me, but I'm not a fan of Amsoil products because they don't publish technical data. Lots of hype, little in the way of facts. Richard 1 on the corvaircenter forum is a lubricant expert and he won't endorse any Amsoil products due to a lack of information.

Some of the Corvair folks that race use the Red Line products. They have a synthetic GL-5 modified for use in transaxles. I'm not endorsing the product, but so far folks claim Red Line 75W90 NS GL-5 works. NOTE -- Red Line has two other products that DO NOT work in a transaxle. One is MS 90 MT that states "Not for use in transaxles with hypoid gears" (The Corvair has a hypoid ring and pinion). They also sell 75W90 GL-5 that is NOT approved for use in transmissions. You have to use the product with "NS" in it that is modified to work with out issues with transmission "yellow metal" synchronizers like the type in a Corvair.

I'm not racing so I don't use synthetics. I just change the lube every 20K miles. Dan The Transmission Man in Los Angeles, CA put it this way "The major cause of Corvair transaxle failures is old dirty lubricant that has never been changed".

Thanks for the Redline info. I use Redline products in my other performance cars but didn't realize they had a modified GL-5 for transaxles. This is the first time I used an Amsoil product. Seems to work fine but I didn't like the buying experience. I felt they wanted me to become a seller of the stuff like Amway or other type of selling pyramids. Just wanted to buy the oil without knowing the secret handshake. I'm usually suspicious of companies like that.
I'll look into the Redline GL-5 NS.

Bob Wilcox
Paso Robles, CA

1966 Turbo Corsa Convertible
1966 140 Corsa Coupe

[bbodie52]

Thu Sep 13, 2018 1:13 pm

...Fortunately Seth Emerson on the corvaircenter forum just announced he is selling reproduction POSI clutch packs. NOS are scarce and $$$$$$...

FYI: I located the Seth Emerson - Positraction Clutch Plate Pack information that was referred to above. The web-page contains additional comments, but the Positraction Clutch Plate Pack does not yet appear on his referenced website.



http://corvaircenter.com/phorum/read.ph ... 996,991097

New Positraction Plate kits available
Posted by: Seth Emerson
Date: August 15, 2018 11:22AM

As shown at the Pittsburgh Convention – Now Available for sale

Brand New Positraction Clutch plate packs for the Corvair differential.
Fits all years 1962-1969
Correct Bellville Washers for preload – All 5 internal pieces included
Slightly higher preload than stock – No need for thicker spacers.
Available now - List price is $125 - Introductory Price $100 + $7 shipping (+ $7.25 sales tax if shipped to a California address.)
24 packs available now, more to come.

Performance Corvair
3462 Kirkwood Dr.
San Jose, CA 95117

Seth Emerson

Check my new Performance Corvair Web site https://www.perfvair.com/

Seth Emerson - Positraction Clutch Plate Pack

Positraction maintenance information begins on page 4-21 of the attached 1965 Corvair Chassis Shop Manual - SECTION 4 - REAR AXLE.

[bbodie52]

MAX GEAR – HIGH PERFORMANCE SYNTHETIC GEAR OIL
Max Gear – High Performance Synthetic Gear Oil
Max Gear is recommended for use in truck and automotive front or rear differentials, manual transmissions and lower gear units of marine engines that specify use of an API GL-5 or GL-4 fluid. It is non-corrosive to soft yellow metals (brass, bronze, copper, etc.) and synchronizer safe. Specially designed to extend gear and bearing life, Max Gear provides superior corrosion protection over competing conventional and synthetic gear oils.

We engineered this ultra-tough, high performance automotive hypoid gear oil to provide maximum protection to heavily loaded gears while maximizing power throughout the drive train. Max Gear outperforms ordinary gear oils by combining the highest quality synthetic oils with Royal Purple’s proprietary Synerlec® additive technology.

Max Gear makes gears run smoother, quieter, cooler and longer without overhauls. A direct reduction of drag in the drive train has huge advantage for trucks and other 4-wheel drive vehicles: better gas mileage. Max Gear is formulated with a friction modifier additive – no additional additives are necessary.

Max Gear is available in the following viscosities: 75W-90, 75W-140, 80W-90, 85W-140 and SAE 90

All Max-Gear oils contain limited-slip friction modifier. Max Gear oils contain the limited-slip friction modifier necessary for proper function of limited-slip differentials. There is no need or benefit to adding additional limited-slip friction modifier

Please email rpautotech@royalpurple.com. Our experts can answer any questions you may have.

For further information or questions please contact Royal Purple technical support directly by email or by phone.
http://www.royalpurpleconsumer.com/contact/
Phone: 281-354-8600
Toll Free: 888-382-6300

http://www.royalpurpleconsumer.com/products/max-gear/

If you have any doubt, just watch this...

Royal Purple ROY01300 Max Gear 75W90 Synthetic Lube, 1 Quart
$22.08/qt. https://www.amazon.com/Royal-Purple-ROY ... 0+gear+oil

Royal Purple 06300 75w90 Max Gear Oil Case, 6 quart, 1 Pack
$93.92 ($15.65/qt.) https://www.amazon.com/Royal-Purple-063 ... Z9FXFP989B

[66vairguy]

Brad - Seth offered a "new product" discount for Sept. on the corvaircenter forum. I recall he said on Oct. 1st. the clutch pack will be "offically" released and the price goes UP.

See ---- http://corvaircenter.com/phorum/read.php?1,993894

[martyscarr]

FWIW, Paul Cangialosi, author of "How to Build and Modify High Performance Manual Transmissions" has mentioned in at least one of his videos (GearBoxVideo on youtube) he has seen no detrimental effects on synchros with long term use of GL5 gear oil.

[bbodie52]

There are numerous published comments from experts in the field that would strongly disagree with the above comment. A few are posted below. I would never take the risk of loading GL-5 gear oil into any manual transmission, or into a Corvair transaxle, which does not isolate the differential gear oil from the transmission section. Why would you want to take the risk of damaging your Corvair transmission? GL-5 gear lubricant is fine in a Corvair differential that is part of a Powerglide transaxle, since the automatic transmission is isolated from the differential gear lubricant. But manual transmission transaxles should only use GL-4 gear lube, or the GL-4/GL-5 rated synthetic like the Royal Purple Max Gear synthetic that is specifically formulated to be fully compatible with manual transmissions and the "yellow metals" they contain.

I've read that GL-5 fluid is no good for Brass components in the transmission. GL-4 fluid is the way to go. Stay away from anything that says GL-5

Gear oil is a lubricant made specifically for transmissions, transfer cases, and differentials in automobiles, trucks, and other machinery. It is of a higher viscosity to better protect the gears and usually is associated with a strong sulfur smell. The high viscosity ensures transfer of lubricant throughout the gear train. This is necessary since the devices needing this heavy oil do not have pumps for transferring the oil with only a portion of the lowermost gears bathed in an oil sump. This heavy oil can create viscous drag leading to inefficiencies in vehicle operation. Some modern automatic transaxles (integrated transmission and differential) do not use a heavy oil at all but lubricate with the lower viscosity hydraulic fluid, which is available at pressure within the automatic transmission.
Most lubricants for manual gearboxes and differentials are hypoid gear oils. These contain extreme pressure (EP) additives and antiwear additives to cope with the sliding action of hypoid bevel gears.
EP additives which contain phosphorous/sulfurous compounds are corrosive to yellow metals such as the copper and/or brass used in bushings and synchronizers; the GL1 class of gear oils does not contain any EP additives and thus finds use in applications which contain parts made of yellow metals.
GL-5 is not necessarily backward-compatible in synchro-mesh transmissions which are designed for a GL-4 oil: GL-5 has a lower coefficient of friction due to the higher concentration of EP additives over GL-4, and thus synchros can not engage as effectively. Also, transmissions which explicitly call for GL-4 oil may have been designed around this lower concentration of EP additives and thus may contain yellow metal parts which GL-5 will corrode.

http://en.wikipedia.org/wiki/Gear_oil

Question:
Clarify Comments on Use of GL-5 vs. GL-4 Gear Oil
Concerning the GL-5 gear oil, on your website you state the following: "Mobil 1 Synthetic Gear Lubricant LS 75W-90 can also be used in rear axles where API Service GL-4 lubricant is recommended." However, you also say in this "Ask Mobil" section that: "Mobil 1 Synthetic Gear Oil is recommended for all applications where a GL-5 lubricant is specified. GL-5 type lubricants, which have a higher level of additive chemistry, can be corrosive to yellow metals such as copper, brass, etc., and in these applications a GL-4 product is usually specified." Can you clarify this disconnect here? Thank you.
-- John Goetz, Newport News, VA

Answer:
There are transmission applications that recommend API GL-4 type products where we would not recommend using an API GL-5 fluid because transmissions typically have components made from “yellow” metals. However real axles where GL-4 fluids are recommended do not have “yellow” metal components. As a result, the application of an API GL-5 fluid is acceptable.

http://www.mobiloil.com/USA-English/Mot ... r_Oil.aspx

Max Gear is recommended for use in truck and automotive front or rear differentials, manual transmissions and lower gear units of marine engines that specify use of an API GL-5 or GL-4 fluid. It is non-corrosive to soft yellow metals (brass, bronze, copper, etc.) and synchronizer safe. Specially designed to extend gear and bearing life, Max Gear provides superior corrosion protection over competing conventional and synthetic gear oils.

HOWEVER...

After viewing some of Paul Cangialosi's videos, you cannot help but be impressed by his knowledge, experience, etc. So why the dispute about GL-4 vs. GL-5 lubricants? Well, I located his video that addresses lubricants, and it is here that Paul Cangialosi explains his position on this subject. The entire video is interesting, but if you want to jump forward to the specific discussion about manual transmission lubricants, advance the video to 11:20. He makes some interesting and convincing points, and talks about his recommendations and preferences. He does confirm that he does like the Royal Purple Max Gear synthetic that is mentioned above.

GearBoxVideo
Published on May 25, 2017

I discuss some of the new oils today for manual transmissions and take apart a Muncie 4 speed that welded up. There has been a great deal of misinformation about GL-5 based oils corroding synchronizer rings. I've never seen this happen in 1000's of tranmissions I've serviced. We have seen more GL-4 based oils come to the market within the past 3 years, but prior to that everyone was OK using GL-5 oil for the past 20 to 30 years. The new GL-4 oils are a plus because we now have better formulated oils for our muscle car transmissions.

Get my Muncie Book here: http://amzn.to/2qZU6lL
My website: http://www.5speeds.com
GL4 Oil - http://www.gl4oil.com

[66vairguy]

FWIW, Paul Cangialosi, author of "How to Build and Modify High Performance Manual Transmissions" has mentioned in at least one of his videos (GearBoxVideo on youtube) he has seen no detrimental effects on synchros with long term use of GL5 gear oil.

Marty - Some GL-5 lubricants are "buffered" so they won't attach "yellow" metals. However that's only part of the problem. The older style synchros need a some friction to work. Often GL-5 lube is too "slippery" for lack of a better term and the synchros won't work properly.

Paul C. is building "performance" manuals, which often are quite different versus a "street" transmission.

RedLine products says their GL-5 "NS" is modified to not attach "yellow" metals and offer the proper friction coefficient for synchronizers. I have not used it, but some say it works for them in Corvairs.

Looking a new lubricants is interesting, but if you change the Corvair transaxle gear oil between 20K 30K miles with plain old GL-4 and don't abuse the transaxle it should go 100K miles or more without issue. Of course if your going racing that puts greater demands on the transaxle.

[jetcat]

Bob - Yes synthetics seem to be an issue with POSI, although I don't know why. When I had a new 2000 Chevy Silverado truck I took it in for routine service and I was told my rear end lube would be changed at NO cost to a standard lubricant because there was an issue with the synthetic lube installed at the factory.

Just me, but I'm not a fan of Amsoil products because they don't publish technical data. Lots of hype, little in the way of facts. Richard 1 on the corvaircenter forum is a lubricant expert and he won't endorse any Amsoil products due to a lack of information.

Some of the Corvair folks that race use the Red Line products. They have a synthetic GL-5 modified for use in transaxles. I'm not endorsing the product, but so far folks claim Red Line 75W90 NS GL-5 works. NOTE -- Red Line has two other products that DO NOT work in a transaxle. One is MS 90 MT that states "Not for use in transaxles with hypoid gears" (The Corvair has a hypoid ring and pinion). They also sell 75W90 GL-5 that is NOT approved for use in transmissions. You have to use the product with "NS" in it that is modified to work with out issues with transmission "yellow metal" synchronizers like the type in a Corvair.

I'm not racing so I don't use synthetics. I just change the lube every 20K miles. Dan The Transmission Man in Los Angeles, CA put it this way "The major cause of Corvair transaxle failures is old dirty lubricant that has never been changed".

Thanks for the Redline info. I use Redline products in my other performance cars but didn't realize they had a modified GL-5 for transaxles. This is the first time I used an Amsoil product. Seems to work fine but I didn't like the buying experience. I felt they wanted me to become a seller of the stuff like Amway or other type of selling pyramids. Just wanted to buy the oil without knowing the secret handshake. I'm usually suspicious of companies like that.
I'll look into the Redline GL-5 NS.

Bob Wilcox
Paso Robles, CA

1966 Turbo Corsa Convertible
1966 140 Corsa Coupe

A follow up to my posi/oil experience. Got the rebuilt transaxle, including Seth's new posi plates, installed in my coupe. Wound up using the Amsoil GL-4. Put about 100 miles on it so far. Shifts smoothly and no shudder in sweeping turns. No additives needed. 95 lbs breakaway torque at the wheel. Very happy with the results! Slooowly becoming a Amsoil fan. Let's see how it holds up after a few k miles from here.

Bob Wilcox
Paso Robles, CA

1966 Turbo Corsa Convertible
1966 140 Corsa Coupe