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Username Post: Really Thick gear Lube        (Topic#249403)
Oldengineer 
Contributor
Posts: 444

Loc: Cross Lanes, WV
Reg: 08-16-10
09-17-10 09:24 PM - Post#1977572    

I finally got around to pulling the differential fill plug on my recently acquired 48 Fleetmaster. THe differential was full, but, the gear lube in it is really thick - about the consistency of thick molasses. It has almost no odor and there's no sulfur smell at all. Now I'm wondering what the stuff is, and, what I should do with it.

Regards:
Oldengineer



 




Gene_Schneider 
Ultra Senior Member
Posts: 12007

Loc: Wisconsin..USA
Reg: 09-27-02
09-18-10 09:28 PM - Post#1977920    
    In response to Oldengineer

Drain it out. Then add a quart of 85W140, spin things around to flush and drain and refill with 3 1/2 pints of 85W-140 (can use #90 if you wish.

I would drin the transmission also and use the 85W-140 for sure in it. It helps to chushion the gear rattle (clutch chatter) when hot.

ChevGene 1934 Master sedan 1939 Master DeLuxe Town Sedan 1950 Styline DeLuxe Power Glide 1957 Nomad 283 PG 1963 Corvair Convertible


 
Oldengineer 
Contributor
Posts: 444

Loc: Cross Lanes, WV
Reg: 08-16-10
09-19-10 07:38 PM - Post#1978311    
    In response to Gene_Schneider

Gene:

I put a fresh load of 85-90 in the tranny, and, it seems to be doing fine. The rear end, I suspect, is full of 600 weight gear oil. I'll try your suggestion on it, and, put in 85 - 140 in.

Regards:
Oldengineer



Edited by Oldengineer on 09-19-10 07:39 PM. Reason for edit: No reason given.

 
Road Runner 
Forum Newbie
Posts: 86
Road Runner
Loc: CA Mountain Desert
Reg: 02-07-07
09-26-10 04:08 PM - Post#1981156    
    In response to Oldengineer

Only use GL-4 rated gear oil in your synchro-mesh transmission.

Avoid GL-5 gear oil. It has twice the amount of sulfur/phosphorous additive, which will slowly peel off the surface of the brass parts.
You can confirm this, when you drain GL-5 oil after some use and the oil looks like thick metallic copper paint in direct sunlight.

GL-4 rated gear oil is a little harder to find these days.
I get this one from the NAPA store: Gear Oil - Automotive, 85W90; 1 GAL

I also use this for my rear end, although GL-5 would be alright, since there are no yellow metal parts.

Transmission and differential oil should be changed anually, especially in colder and damper climate zones.





On the road every day ...

1948 Coupe

1952 Truck


 
David Hayward 
Deceased RIP David
Posts: 7051
David Hayward
Age: 61
Loc: New Forest, UK
Reg: 04-10-99
09-26-10 11:28 PM - Post#1981330    
    In response to Road Runner

Made sticky!

Automotive Historian, Writer & Author

Avatar: sole surviving 1939 Chevrolet truck assembled in Southampton, England


 
Sawtooth0645 
Forum Newbie
Posts: 94
Sawtooth0645
Loc: Colorado Front Range
Reg: 10-02-10
05-01-11 10:56 AM - Post#2084493    
    In response to Oldengineer

Oldengineer-
I am about to do the same thing to my diff, but wondered what it would take to get the old thick stuff out. Did you have to do anything special to drain something the consistency of thick molasses?



 
49Stovebolt 
Forum Newbie
Posts: 57

Loc: NE Florida
Reg: 11-27-12
11-28-12 11:26 AM - Post#2293080    
    In response to Oldengineer

It may be STP



 
Road Runner 
Forum Newbie
Posts: 86
Road Runner
Loc: CA Mountain Desert
Reg: 02-07-07
05-17-13 04:57 PM - Post#2346493    
    In response to Oldengineer

Pennzoil came out with a special Synchromesh fluid...

Pennzoil Synchromesh Transmission Fluid


It's mineral oil based like the old-time fluids and much thinner compared to 85W-90 GL-4 fluids.

It's rated SAE 80 - Not ideal for the summer months, but great for cold temps, with easier shifting, especially after a cold start.



On the road every day ...

1948 Coupe

1952 Truck


 
LRH 
Contributor
Posts: 109

Loc: USA
Reg: 10-27-08
05-17-13 05:35 PM - Post#2346504    
    In response to Road Runner

The GL-5 lube with GL-5/MT-1 uses different additives VS more sulfur so they are compatible with yellow metals. MT or MT-1 alone do not meet spec, and GL-5 won't, it has to meet and be labeled GL-5/MT-1. Some synthetic manual trans lube have the large letters MT on the container not to mislead, but to signify it is for manual trans. Just offered this in case some are not finding GL-4.



 
Road Runner 
Forum Newbie
Posts: 86
Road Runner
Loc: CA Mountain Desert
Reg: 02-07-07
08-01-14 11:38 AM - Post#2473567    
    In response to Road Runner

WARNING !


Do NOT use the PENNZOIL SYNCHROMESH MANUAL TRANSMISSION FLUID I mentioned in my last post, especially in the summer months.

It is too thin/light.

I just called the Pennzoil techline and they also don't recommend it and said to either use GL-4 mineral oil or even better GL-4 synthetic oil.



On the road every day ...

1948 Coupe

1952 Truck


 
2blu52 
"16th Year" Silver Supporting Member
Posts: 17988
2blu52
Age: 84
Loc: Montana
Reg: 03-12-02
08-01-14 08:11 PM - Post#2473654    
    In response to Sawtooth0645

  • Sawtooth0645 Said:
Oldengineer-
I am about to do the same thing to my diff, but wondered what it would take to get the old thick stuff out. Did you have to do anything special to drain something the consistency of thick molasses?


Just pull the bottom bolt holding the cover in place, place a pan under it and let gravity take its course.

"PEACE IS THAT GLORIUS MOMENT IN HISTORY WHEN EVERY ONE STANDS AROUND RELOADING"

THOMAS JEFFERSON


 
Road Runner 
Forum Newbie
Posts: 86
Road Runner
Loc: CA Mountain Desert
Reg: 02-07-07
08-02-14 07:12 AM - Post#2473722    
    In response to Road Runner

I posted the same info on another forum and somebody recommended against using synthetic base fluid ...


"... I'd be cautious of using full synthetic lube in an older trans with brass blocker rings. The extra slippery lube can make it difficult for the brass rings to get the needed "bite" on the synchronizer hubs. You might end up with some gear clash even on a new or freshly rebuilt transmission. The increased slipperiness of the synthetic fluids, while beneficial for most of the transmission, actually over-lubricates the older style synchronizers."



On the road every day ...

1948 Coupe

1952 Truck


 




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