Gear oil for trans and rearends

[Johnboy]

What oil to use in trans and rears I have heard from several people to use 80w 90 although the the manufacturer say use the new synthetic stuff any thoughts?

[Texasdude74]

Transmissions and rear ends are about the only reliable things left on the newer trucks. The 50w synthetic changed every 250k seems to get most guys to 1.5-2M miles. I don't see anything to be gained by running old school, molasses looking mineral oil in there.

[Rawze]

(12-08-2016 )Texasdude74 Wrote:  Transmissions and rear ends are about the only reliable things left on the newer trucks. The 50w synthetic changed every 250k seems to get most guys to 1.5-2M miles. I don't see anything to be gained by running old school, molasses looking mineral oil in there.

If you run with high torque,... 75-90 synthetic in tyranny for better life. Highway and dry-van reefer, 80k or less, .. 50w is fine. easier to shift.

rear ends,.. 75-90 or 85-140. It helps keep the backlash down in the bearings and increases tire edge wear life. As well, longer gear train life, and less chance of wheel seals bleeding when it gets warm.

[Jarhead79]

No matter what lube is used, at 1 million don't expect rear end to hold up if you don't change out pinion bearings. When they go out your gears will snap teeth. I've had that happen. It was company truck not sure if oil was ever changed.

[Johnboy]

Honestly the not changing the oil is the biggest reason I see rearends go for some reason people seem to think the synthetic oil doesn't need to be changed.
Personally I use the synthetic with half a gallon of lucas in the rearends and 50w in the transmission. I have thought about changing to conventional 80w 90 after an internal cooler cracked in a trans and filled it with antifreeze I drained and filled it with 80w90 to get it home.
That was the best it had ever shifted literally clicked in and out of gear where it had always rumbled a little bit. I was just curious if any of you had tried it thanks for the reply.

[Rawze]

(12-10-2016 )Johnboy Wrote:  Honestly the not changing the oil is the biggest reason I see rearends go for some reason people seem to think the synthetic oil doesn't need to be changed.
Personally I use the synthetic with half a gallon of lucas in the rearends and 50w in the transmission. I have thought about changing to conventional 80w 90 after an internal cooler cracked in a trans and filled it with antifreeze I drained and filled it with 80w90 to get it home.
That was the best it had ever shifted literally clicked in and out of gear where it had always rumbled a little bit. I was just curious if any of you had tried it thanks for the reply.

The heavier weight oil is good for them as they wear.

I have seen a lot of tricks tried by various people to extend the life of gearboxes over the years. Gearboxes from rear ends, to spindle heads in machinery, to high-precision axis gearboxes, etc... and at the end of the day,.. nothing whatsoever beats higher hydraulic pressure ratings between components. -- Nothing, no matter what type of oil it is as long as it has decent additives in it.-- I.E. -- using a slightly thinker oil.

I have even seen guys use thinner, really expensive, special synthetic, high dollar foreign oils, and treat components with very expensive coatings, and compare them to a cheapo-, half decent thicker oil,.. and still loose.

[Brock]

(12-09-2016 )Rawze Wrote:  

(12-08-2016 )Texasdude74 Wrote:  Transmissions and rear ends are about the only reliable things left on the newer trucks. The 50w synthetic changed every 250k seems to get most guys to 1.5-2M miles. I don't see anything to be gained by running old school, molasses looking mineral oil in there.

If you run with high torque,... 75-90 synthetic in tyranny for better life. Highway and dry-van reefer, 80k or less, .. 50w is fine. easier to shift.

rear ends,.. 75-90 or 85-140. It helps keep the backlash down in the bearings and increases tire edge wear life. As well, longer gear train life, and less chance of wheel seals bleeding when it gets warm.

Odd. I was told by Eaton that under no circumstances could you use a 75/90 gear lube or anything of that nature. They say there are galleries that are not wide enough to support the thicker oil and you will run components dry causing premature wear.

I wanted to know because I was considering doing it.

[kryten]

These pictures kinda fit this thread. They are of my rear diff plugs when I changed oil back in April.

This is the fill plug.



This is the drain plug



Oil was changed right around the 800000 km mark as per OEM recommendations. There was no real hard filings on the plugs I could feel, just a metallic fuzz. The front diff plugs were similar but maybe 25% less fuzz. I don't think I'll be letting it go that far again.

[Hammerhead]

(12-09-2016 )Rawze Wrote:  If you run with high torque,... 75-90 synthetic in tyranny for better life. Highway and dry-van reefer, 80k or less, .. 50w is fine. easier to shift.

rear ends,.. 75-90 or 85-140. It helps keep the backlash down in the bearings and increases tire edge wear life. As well, longer gear train life, and less chance of wheel seals bleeding when it gets warm.

(12-10-2016 )Brock Wrote:  Odd. I was told by Eaton that under no circumstances could you use a 75/90 gear lube or anything of that nature. They say there are galleries that are not wide enough to support the thicker oil and you will run components dry causing premature wear.

I wanted to know because I was considering doing it.

I run above average torque load so I use 75W90 synthetic in my transmission. For any northerner pulling B-trains, I'd recommend it. I have actually found that my tranny runs cooler and quieter with it over 50W
I'd like to run 85W140 in my diff's because of my workload, but being from Canada running OS/OW, I routinely end up parked for up to 16hrs between travel allowances, and at -30C I think it would be too thick and would lead to premature wear from lube starvation getting warmed up...and synthetic oil is too costly to switch grades twice a year with the seasons.