Survey - what fluid is everyone running in their A833 4 speeds?

[Paul_G]

Lots of info on this subject. I went with penzoil synchromesh because Napa has it on the shelf and it was cheap, like $8 quart. This video debunks the part about GL5 damaging the synchro's. It is a good watch if you start at the beginning, you can forward to 11:25 and he talks about the GL4/GL5 issue.

 

[Mebsuta]

Sometimes GL-5 80w-90, lately GL-4 85w-90. I few months ago I topped it off with 20w-50 motor oil because I didn't feel like hunting around for GL-4. I don't think the antique transmission in my car knows what kind of oil is in there, as long as it doesn't get low.

 

[wyrmrider]

Not exactly
Oil analysis shows more Cu from GL5 than GL4
his viscosity demo is great but viscosity is very temp dependent
couple of things there to check out
glad to see what works for him

 

[Zplane]

80/90 with a bottle of mopar limited slip differential additive, almost shifts itself

 

[AR67GTX]

I last bought GL-4 at NAPA a few years ago. I think the GL-5 versus brass issue is mostly myth based on some persuasive arguments on Corvette Forums so either one will do fine. But if you want what they were originally filled with back in the era you can still get it.

 

[67RT]

Lucas 75w 140.

 

[wyrmrider]

REDLINE MTL
or what Richard said above
or here's another
https://www.discoveryparts.com/race...n-75w85-gl-4-gear-oil-quart-driven-00830.html
https://www.racerpartswholesale.com/product/RedLineOilMT85GearOil50504/MotorcycleGearOil
https://www.castrol.com/en_au/austr...ual-transmission-fluids/syntrans-75W-85w.html Castrol Syntorq,
Valvoline Synpower
from allpar
Mopar Synthetic 75W85 Manual Transmission Lubricant
The 5600 can be serviced with a Pennzoil Syncromesh oil — it has the Chrysler endorsement on the bottle.”
Mopar P/N 4974459 (Material Specification 9070) 75W85 manual transmission lubricant, and GM Synthetic Manual Transmission Fluid (P/N 12346190; in Canada 10953477)

 

[wyrmrider]

75-140 in a diff if you are towing in the desert
not in a synchro late model trans
no posi juice in a trans either all you are doing is diluting your lube

 

[wyrmrider]

finding increased brass in samples is not a myth
varies with the trans
either loading or brass formula
so why even think of using GL-5
and BTW all formulas have changed in the last 10 years
the modern GL-4s have completely different ep formulas
use a GL4 from a modern spec like the trucks with NV trans or foreign cars
The synthetic oils film strength takes less additives and does not shear down like dino oil

 

[AR67GTX]

finding increased brass in samples is not a myth
varies with the trans
either loading or brass formula
so why even think of using GL-5
and BTW all formulas have changed in the last 10 years
the modern GL-4s have completely different ep formulas
use a GL4 from a modern spec like the trucks with NV trans or foreign cars
The synthetic oils film strength takes less additives and does not shear down like dino oil

I'll let you and the old retired GM engineers fight out the GL4 vs GL5 lube myth (Ref DukeSW in the attached thread). He and his friends have pretty much beat us into submission that the modern GL5 formulation is the closest to the original Mil Std in use back in that era. FWIW - I still use GL4 because it's still available.
https://www.corvetteforum.com/forums/c1-and-c2-corvettes/3972693-oil-for-muncie-4-speed.html

 

[wyrmrider]

Don't know any retred gm engineers and never read any posts
have managed fleets and done plenty of lube and oil analysis and still have friends that do
only raced a few munices
did run a MOPAR t-10 which grenades- AMC Super T10 was much stronger as is the 883 and Toploader
The MOpar 3 speed that cam in the 413 MAX wedge was strong enough but slow to shift and wide ratios
still have it somewhere and the early 4 speed with the companion flange instead of slip yoke if anyone needs one
(but even buried deeper than the W2 head I promised Krooser at least I know where it is)