Opinion - Which is worse ?

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acarlson
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Opinion - Which is worse ?

Post by acarlson »

GL-4 in the differential or GL-5 in the 4 speed tranny ?

Alec
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Re: Opinion - Which is worse ?

Post by Wagon Master »

Definitely running GL-5 in a trans. is worse. Hundreds of thousands of diffs. were run on GL-4 before GL-5 was released.
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bbodie52
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Re: Opinion - Which is worse ?

Post by bbodie52 »

GL-5 gear lube can damage the "yellow metal" gear components in a manual transmission. Since the Corvair manual transmission transaxle shares the gear lube between the transmission and the differential, GL-4 is the only lubricant that should be used in the manual transaxle.

GL-5 is corrosive to the synchros and other "yellow metal" components in transmissions. It is not damaging to differentials, but in Corvair transaxles the lubricant is shared between the transmission and the differential, so GL-5 should NOT be used in a manual transmission transaxle. If you have already filled your Corvair manual transmission-based transaxle with GL-5, it should be drained and replaced with GL-4 gear lube to minimize damage and wear to the transmission components.
bbodie52 wrote: :think: I tend to prefer synthetic motor oils and synthetic gear oil. :nono: HOWEVER... whatever you choose be sure to stay away from GL-5 gear oil. GL-5 would be OK in the differential, but not in a Corvair manual transmission. Since the lubrication contents of the transmission and differential are shared between the two components in the Corvair manual transaxle, you definitely do not want to use GL-5 in a Corvair manual transaxle.
Ask Mobil wrote: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.
:link: http://www.mobiloil.com/USA-English/Mot ... r_Oil.aspx

Mobil 1 Synthetic Gear Oil appears to be a GL-5 lubricant, and therefore should not be used in a Corvair transaxle. It could be used in a Corvair automatic transaxle, since the differential would not be damaged by GL-5 lubricants.

Image Pennzoil produces both GL-4 and GL-5 synthetic gear oils. The bottle with the blue top is clearly labeled GL-4. It is a high-quality lubricant and would work well in a Corvair transaxle. The bottle with the yellow top is GL-5, and using it in a Corvair manual transaxle could damage the transmission.

Whether you choose a brand of synthetic or non-synthetic gear oil, always be sure the gear oil is rated GL-4. If you have a Positraction Limited Slip differential, also be certain that the gear oil you choose is designed for use in a Limited Slip (LS) differential. (LS gear oil will also work OK in a non-limited slip differential).
SYNTHETIC SAE 75W-90 GL-4

Long Service Life, Wide Temperature Use Gear Oil

PRODUCT DESCRIPTION PENNZOIL® SYNTHETIC SAE 75W-90 GL-4 combines a premium performance gear oil additive package with high-quality synthetic base stocks. The result is a gear oil that provides excellent low temperature fluidity for safe lubrication during very low temperature transmission and transaxle startup, and also maintains a thick protective oil film during extremely hot operating conditions.

PENNZOIL® SYNTHETIC SAE 75W-90 GL-4 is formulated with all the performance additives necessary for outstanding protection of gears and bearings. It contains extreme pressure agents which protect against shock loading and wear. It is formulated to be compatible with copper containing alloys and soft metals found in synchronizers. Foam inhibitors protect against oil aeration and foam, which can rupture the lubricant film and cause wear due to lack of lubrication. Special rust inhibitors are incorporated into PENNZOIL® SYNTHETIC SAE 75W-90 GL-4 to protect against corrosion than can result from condensation. Oxidation inhibitors are included to further enhance this synthetic’s inherent oxidation stability, resulting in a lubricant with exceptionally long service life and excellent resistance to deposit and sludge formation during high temperature operation.

PENNZOIL® SYNTHETIC SAE 75W-90 GL-4 meets all the requirements of API Service Classification GL-4 .

APPLICATION
PENNZOIL® SYNTHETIC SAE 75W-90 GL-4 is designed primarily for the lubrication of manual transmissions and
transaxles requiring an API GL-4 lubricant. It can be used in passenger cars, light trucks, sport utility vehicles, and vans. It continues to flow at very low temperatures, providing especially good protection of gears and bearings in extreme cold weather. It also provides excellent service in hot climates by not thinning at high temperatures, thereby maintaining a full film of protective lubricant on gear teeth. In hot running gear boxes, it allows longer service due to the excellent stability of the synthetic base stocks used in it. It can be used in applications that call for General Motors part number 12345371 gear oil.
:link: http://www.amazon.com/Pennzoil-56076-75 ... B00C43BLLS
Image

Image
bbodie52 wrote:The shop manual indicates the rear axle (differential) has a capacity of 4½ pints. It also states that the 3-speed manual transmission has a capacity of 2.2 pints, while the 4-speed transmission has a capacity of 3.6 pints. So the combined capacity of the 4-speed transaxle would be approximately 8.1 pints (4.05 quarts). NOTE: In 1966-1969 the Corvair 4-speed manual transmission changed to a Saginaw unit, which might have a slightly different capacity than the earlier four-speed. I don't have a 1966 or later supplement, so I'm not sure of the lubricant capacity for the 1966-1969 transmission.

I found a further discussion about GL-4 vs. GL-5 use in Corvairs on the Corvair Center website, should you wish to read it...

:link: http://corvaircenter.com/phorum/read.ph ... 887,401578

Here is a list of other GL-4 products. They also mentioned that the Pennzoil GL-4 synthetic lube may be difficult to find in some retail outlets, as the product may be classified as a "slow mover" since it caters to manual transmission owners who need GL-4, but not necessarily to a majority of owners needing only lubricant for a differential in automatic transmission cars which are fine with a GL-5 product. If you want something like the Pennzoil GL-4 synthetic lubricant, you may have to call around. I simply order it from a source like Amazon.com and have it on my doorstep in a couple of days.
  • Amsoil Synthetic manual Transmission and Transaxle Gear Lube 75W-90 GL-4
  • Citgo Citgear Standard XD 75W-90 GL-4
  • Pennzoil Gearplus 80W-90 GL-4
  • Pennzoil Synthetic 75W-90 GL-4 (from the spec sheet, the best overall viscosity curve)
  • Quaker State Multi-purpose Gear Lubricant 80W-90 GL-4
  • Redline MT-90 Synthetic Transmission Fluid 75W-90 GL-4
  • Shell Spirax G SAE 90 GL-4 (I do not recommend this due to it's extremely high low temperature viscosity.)
  • Shell Spirax GX 80W-90 GL-4 ( do not recommend this due to it's low high temperature viscosity)
  • Chevron had a product called Chevron Manual Transaxle oil that was excellent, but I cannot find it except in clearance sites. I don't know if it has been replaced.
The following article by Richard Widman is a good technical article on this subject...
The Difference between GL-4 and GL-5 Gear Oils - by Richard Widman.pdf
The Difference between GL-4 and GL-5 Gear Oils - by Richard Widman
(809.17 KiB) Downloaded 17 times
Brad Bodie
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acarlson
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Re: Opinion - Which is worse ?

Post by acarlson »

I've read Widman's paper. Unfortunately Penzoil 75w-90 GL-4 has been discontinued. However your comments have supported my own opinion. Thanks.

Alec
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Re: Opinion - Which is worse ?

Post by 66vairguy »

Widman's paper is good. One thing he discusses is not only the corrosion problem with GL-5 (buffered can alleviate the issue), but he noticed GL-5 tends to increase wear of the yellow metal components even when it's buffered to prevent corrosion.

There is no shortage of claims and ideas about Corvair transaxle lube, a lot of it is general opinions.

Sta-Lube GL-4 85-90 is a bit thick, but is better than old lube and is affordable. It works as long as you don't drive the car in cold conditions (trans won't shift until warmed up). In the warm South it works fine, both my Corvairs use it.

Amsoil and Redline have products that are pricey. The problem I have (and Widman had) was you can't get a specification backed answer from Amsoil. Redline sells a special "NS" GL-5 synthetic that "supposedly" is formulated to allow synchros to grab properly and has corrosion inhibitors to protect the "yellow metals" - but again Widman could not get a specification based answer to explain how this is done.

Another "Boutique" lube is made by Brad Penn called "Classic GL-4 80W90". It's the right weight, not a synthetic, and the price is close to the Sta-Lube GL-4 (if you buy Sta-Lube by the gallon). Sadly not much about Brad Penn performance except ancedotal comments.

The more I read at the "off brand" oil sites the more I feel like I'm listening to snake oil salesmen.
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Re: Opinion - Which is worse ?

Post by bbodie52 »

:search: Amazon.com

ImagePennzoil 56076 75W-90 Synthetic Gear Oil (GL-4) - 1 Quart
$34.69 (Amazon.com Subscribe & Save Price: $29.49/qt.)
:link: https://www.amazon.com/Pennzoil-56076-7 ... nnzoil+gl4

ImageSta-Lube SL24239 API/GL-4 Multi-Purpose Hypoid Gear Oil - 1 gal
$27.60 (Amazon.com Subscribe & Save Price: $23.46/gal. (15% Discount) or $26.22 (5% Discount))
:link: https://www.amazon.com/Sta-Lube-SL24239 ... nnzoil+gl4

ImageRed Line 50305 MT-90 75W90 GL-4 Gear Oil - 1 Gallon
$55.93
:link: https://www.amazon.com/Red-Line-50305-M ... nnzoil+gl4

106 Results when searching Amazon.com for "GL4"
:link: https://www.amazon.com/s/ref=sr_gnr_fkm ... 1486848662
Brad Bodie
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acarlson
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Re: Opinion - Which is worse ?

Post by acarlson »

Brad - did you see the Amazon Penzoil price ??? :eek: The reason it is so high is it is no longer generally available. I've searched the net and Amazon is the only place it is available. Other company's list it but they don't have any in stock. A few of those at least let you know it's been discontinued and they'll never have any.

Alec
Alec Carlson
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1965 Regal Red Corsa 4 Speed Turbo Convertible
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