The Ford Barn

30-9 · 01-08-2020, 06:51 PM

Is this ok for 39-40 rear?

alanwoodieman · 01-08-2020, 07:21 PM

rear ends can use any # GL but for trans, due to brass synchro's, you need to use GL 1/2/3
I buy mine from tractor supply--ford tractor trans oil

rotorwrench · 01-08-2020, 07:25 PM

The rear axle doesn't care what you put in there. It can take high EP GL5 of any brand 85W/90 or 85W/140 with no problems or worry. The transmission would work with either GL1 or GL4 but the EP levels are too high for GL5.

I use AeroShell W100 in my transmissions. It's SAE-50 grade 100 motor oil with ashless dispersant. I don't use the W100 + (plus) since it has tricrestyl phosphate and that won't work well with yellow metal or sprag clutches in the overdrive unit. SAE 50 is equivalent to straight grade SAE-90 gear lube since they are graded differently for viscosity.

19Fordy · 01-08-2020, 07:51 PM

I use STALUBE GL4 in my 40 transmission and rear.
https://www.amazon.com/Sta-Lube-SL24...530972&sr=8-13

JSeery · 01-08-2020, 08:48 PM

Ford specified mild EP lubricate for transmissions starting in 1941 (same transmission internally), which relates to GL4 in modern terms. As already posted GL4 or GL5 for the rear axle. Also, with modern lubricants multi-grade would be better than straight viscosity IMO.

30-9 · 01-08-2020, 08:59 PM

Sponsored Links (Register now to hide all advertisements)

Thanks Gents.

Jseery are you disagreeing and saying that GL1 is no good for rear?

David J · 01-08-2020, 09:28 PM

I would not use GL1 period . GL1 is straight mineral oil with no EP additives .

Post 4 has a good option [ my choice for steering box , trans , u-joint and rear .

JSeery · 01-08-2020, 09:42 PM

Quote:

Originally Posted by 30-9

Thanks Gents.

Jseery are you disagreeing and saying that GL1 is no good for rear?

As David posted, GL1 has no EP additives, there is a reason Ford switched to Mild EP recommendation in 41 for transmission and much earlier for the rear axles. The 40 chart recommended Mild EP for the rear axle, that is GL4. I'm not sure why you would want to run GL1 in a rear axle, not a good idea. The 32-35 chart recommends EP lubricate for the rear axle, that is GL5. It is E & U on the charts.

Terry,OH · 01-09-2020, 07:15 AM

NAPA sells the Sta-Lube usually have to order it and it is there the next day. SL-24238 is GL-4 and SAE 140, EP. It comes in a one gallon container enough for your differential, transmission and steering box +.

30-9 · 01-09-2020, 07:42 AM

Thanks I was only asking based on first couple of post responses. Stating any GL would work in rear.

JSeery · 01-09-2020, 09:40 AM

Quote:

Originally Posted by 30-9

Thanks I was only asking based on first couple of post responses. Stating any GL would work in rear.

While it is true that any GL would work, the EP additive serves a purpose and that is why Ford recommended it. So while any GL lubricant would work, why not use the one best for the application?

rotorwrench · 01-09-2020, 11:24 AM

A vehicle used with light loads can use GL1. Pickups, trucks, or sedans that carry a larger weight volume would have used at least the GL-3 that was available back in the day. GL-4 replaced GL-3 and made it obsolete.

Tractors and Model Ts use the equivalent to SAE-90 or 140 GL-1 (model Ts used 600W which is roughly SAE 140 equivalent). Worm screw drives and slow movers do just fine on straight mineral with at least the SAE 80 or 90 gear lube viscosity index. The faster they move, the more heat they build so the sulfur & phosphorus based EP additives become more important for them.

When you think about it, the transmission is shifted through 1st & 2nd relatively quickly. After that, it's 1:1 drive straight through the main shafts. The counter shaft is still turning but its only load is the oil its running through. The key to longevity is the additives for corrosion resistance. The NAPA GL-1 only contains anti foaming additive and that's it. The higher EP gear lubes have anti corrosion additives. Even motor oil has corrosion resistance additives. This is what can make it a problem with transmission applications if a vehicle sets for too long. If used regularly then GL-1 could be used for light duty transmission applications.

Ford Freak · 01-09-2020, 12:26 PM

Quote:

Originally Posted by 19Fordy

I use STALUBE GL4 in my 40 transmission and rear.
https://www.amazon.com/Sta-Lube-SL24...530972&sr=8-13

Me too ! Get it through NAPA .

50fordcoupeman · 01-09-2020, 06:27 PM

Quote:

Originally Posted by Ford Freak

Me too ! Get it through NAPA .

Me too.........NAPA.

Branded · 01-09-2020, 09:28 PM

Quote:

Originally Posted by 50fordcoupeman

Me too.........NAPA.

Me too

01-08-2020, 06:51 PM	#1
30-9 Senior Member Join Date: Aug 2014 Location: MA Posts: 888	Napa GL1 Is this ok for 39-40 rear? __________________ Thanks - 30-9 1939, 1940

01-08-2020, 07:21 PM	#2
alanwoodieman Senior Member Join Date: May 2010 Location: upstate SC Posts: 2,963	Re: Napa GL1 rear ends can use any # GL but for trans, due to brass synchro's, you need to use GL 1/2/3 I buy mine from tractor supply--ford tractor trans oil

01-08-2020, 07:25 PM	#3
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,436	Re: Napa GL1 The rear axle doesn't care what you put in there. It can take high EP GL5 of any brand 85W/90 or 85W/140 with no problems or worry. The transmission would work with either GL1 or GL4 but the EP levels are too high for GL5. I use AeroShell W100 in my transmissions. It's SAE-50 grade 100 motor oil with ashless dispersant. I don't use the W100 + (plus) since it has tricrestyl phosphate and that won't work well with yellow metal or sprag clutches in the overdrive unit. SAE 50 is equivalent to straight grade SAE-90 gear lube since they are graded differently for viscosity.

01-08-2020, 07:51 PM	#4
19Fordy Senior Member Join Date: May 2010 Location: Coral Springs FL Posts: 10,943	Re: Napa GL1 I use STALUBE GL4 in my 40 transmission and rear. https://www.amazon.com/Sta-Lube-SL24...530972&sr=8-13

01-08-2020, 08:59 PM	#6
30-9 Senior Member Join Date: Aug 2014 Location: MA Posts: 888	Re: Napa GL1 Sponsored Links (Register now to hide all advertisements) Thanks Gents. Jseery are you disagreeing and saying that GL1 is no good for rear? __________________ Thanks - 30-9 1939, 1940

01-08-2020, 09:28 PM	#7
David J Senior Member Join Date: Jun 2010 Location: St Croix Falls WI Posts: 2,080	Re: Napa GL1 I would not use GL1 period . GL1 is straight mineral oil with no EP additives . Post 4 has a good option [ my choice for steering box , trans , u-joint and rear . Last edited by David J; 01-08-2020 at 10:21 PM. Reason: ADDING

01-09-2020, 07:15 AM	#9
Terry,OH Senior Member Join Date: May 2010 Posts: 4,751	Re: Napa GL1 NAPA sells the Sta-Lube usually have to order it and it is there the next day. SL-24238 is GL-4 and SAE 140, EP. It comes in a one gallon container enough for your differential, transmission and steering box +.

01-09-2020, 07:42 AM	#10
30-9 Senior Member Join Date: Aug 2014 Location: MA Posts: 888	Re: Napa GL1 Thanks I was only asking based on first couple of post responses. Stating any GL would work in rear. __________________ Thanks - 30-9 1939, 1940

01-09-2020, 11:24 AM	#12
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,436	Re: Napa GL1 A vehicle used with light loads can use GL1. Pickups, trucks, or sedans that carry a larger weight volume would have used at least the GL-3 that was available back in the day. GL-4 replaced GL-3 and made it obsolete. Tractors and Model Ts use the equivalent to SAE-90 or 140 GL-1 (model Ts used 600W which is roughly SAE 140 equivalent). Worm screw drives and slow movers do just fine on straight mineral with at least the SAE 80 or 90 gear lube viscosity index. The faster they move, the more heat they build so the sulfur & phosphorus based EP additives become more important for them. When you think about it, the transmission is shifted through 1st & 2nd relatively quickly. After that, it's 1:1 drive straight through the main shafts. The counter shaft is still turning but its only load is the oil its running through. The key to longevity is the additives for corrosion resistance. The NAPA GL-1 only contains anti foaming additive and that's it. The higher EP gear lubes have anti corrosion additives. Even motor oil has corrosion resistance additives. This is what can make it a problem with transmission applications if a vehicle sets for too long. If used regularly then GL-1 could be used for light duty transmission applications.