CK5
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done

Running Amsoil in the 14b, mainly to keep temps down. Seems to have worked, it's not burping out the breather anymore.

Also running Amsoil in the 700r4. Haven't noticed much temp difference but probably wouldn't see it anyway. Just trying to save it from a crazy owner :D
 
75w-140. In all my high torque diesels rears. Besides it's recomended lube for the true Trac in the rear as well.
 
We use BG but have also used Amsoil, Mobil1 and others. It is worth the investment to me to have superior heat resistance in this part of the world.
 
I run Amsoil in everything except for my genset. It would be great in it, especially since its turbocharged, but I just can't justify a 4 gallon oil change.

I have told the story about the guy who kept burning up rear ends in his new Ford hauling horses across a mountain pass.
Ford replaced the internals about 3 times under warranty, and finally replaced the entire assembly. No luck.
I got involved because he was wanting to hook up a temp gauge so he could pull over and let it cool before it smoked the oil.

Right after we got the gauge working, one of the guys on that forum suggested changing to Amsoil.
After that, the rear end never got out of normal operating temp.

I put some in my NP205, and it went from running so warm I could feel it through the floorboards after a hard drive, to my being able to lay my hand on it without discomfort.

I got a reply on another forum about that to the effect that "studies" had shown that synthetic oil did not reduce heat, it just did not transfer it to the case like regular oil, so the case ran cooler.
Plus he posted a link where one of the major gear venders warned against using synthetic with their new gears.

I did not bother trying to dispute his logic.

I really wanted to point out that synthetic oil would have to have insulating properties equal to or better than Styrofoam for that to be true.
Plus, if the gears could not shed the heat better than that, they would eventually melt.

Also, any new motor or moving part that needs to wear during break-in should not use synthetic oil until it is broken in.
Most of the oil makers say that.
They stuff is just too slick, and rings can't seat. I suspect that gears need to wear in the same way.

As for gas mileage increase, I think I can safely say that it does. Your engine has to burn gas to make that wasted heat in the gears.
But, I'm not sure its enough to notice on a day to day basis.

And I seriously doubt that it would ever be cost effective unless the price of gas goes above $20 per gallon.

If you were to plan on driving a car a couple of years and getting rid of it, then I would not use the synthetic.
Just use cheap oil, and let someone else inherit the wear.

But, if you intend to keep it, like I do, then I think its worth it to reduce downtiime.
One of these days, I am going to break down and install a bypass oil filter system. That combined with oil analysis, would decrease wear even more, and make the oil more cost effective.

So, I run Amsoil in my truck, car, and small engines. They pretty much invented the stuff, and I have a local jobber that gives me distributor pricing.......
 
Great post.

I'm a believer in running the synthetic multi-grade gear oil as well. My VW Bug definitely had positive results when running 75W90 Red Line in the transaxle. I also ran it in my Wagoneer axles, as well as in my Suburban (for a while). Although, I logged every fuel fill in the Wagoneer, and continue to log every fuel fill in the Suburban and honestly I may have saved a few tenth's of a mile per gallon. Still worth it in my opinion though. Think about the longevity of the synthetic compared to dino oil.

I'll probably be switching to the Amsoil products soon overall. I will continue to log every fill up, and I am willing to bet I will see a positive change in fuel mileage. That's a good thing in a big ol' Suburban!

Clay
 
I swapped all the lubes in my 2007 dodge dually over to Royal Purple synthetics at the 100,000 mile service. Both axles, manual trans and transfer case.

First thing I notice was how much smoother the manual trans. shifted and much more quiet it was... big difference... and the truck seems to "coast" a lot easier... :dunno:

overall, I saw a small increase in fuel mileage....about 0.7 MPG
 
Synthetics do work, that bit about them not reducing heat is bull!

In 1994 I bought a new Harley dresser and put on a sidecar. Living in AZ heat was an issue and already had oil cooler and Synthetic oil.

But after about an hour highway drive with sidecar on, it was stuck in gear! Never happened without sidecar... so I changed out the trans oil to synthetic and immediately noticed how much easier it shifted! Then the hour cruise on highway and no issues downshifting!
 
Looking to get any MPG increase I can. Why I am thinking with axles and gear box running synth along with the synth in motor should get be closer to 14 I hope.

Synthetics are great, but if you are looking for real gains, its not worth the money.

For the usage, and budget type of this project, I would stick to conventional.

Your money will be better spent elsewhere than on fancy gear oil.
 
Synthetics do work, that bit about them not reducing heat is bull!

In 1994 I bought a new Harley dresser and put on a sidecar. Living in AZ heat was an issue and already had oil cooler and Synthetic oil.

But after about an hour highway drive with sidecar on, it was stuck in gear! Never happened without sidecar... so I changed out the trans oil to synthetic and immediately noticed how much easier it shifted! Then the hour cruise on highway and no issues downshifting!

i had a 08 sportster 1200 went the first 5000 miles with harley dino oil, when i switched to amsoil it improved everything so much, the heat was down, and the shake was cut by 3/4. i went from not being able to use the mirrors to them being crystal clear at all rpm. i use it in everything, my dad has been a dealer since the start back in the earily 70's.
 
i had a 08 sportster 1200 went the first 5000 miles with harley dino oil, when i switched to amsoil it improved everything so much, the heat was down, and the shake was cut by 3/4. i went from not being able to use the mirrors to them being crystal clear at all rpm. i use it in everything, my dad has been a dealer since the start back in the earily 70's.
Since Amsoil has a 10w/40 with zinc and phousporus it's what I use on the flat tappet cam engine in my Suburban... good stuff!

Back to gear oil...

I doubt you'd notice a MPG improvement in this rig. Maybe something that slips through the air at highway speeds and barely needs any throttle? But not a beast like this. It takes a lot of HP to keep up highway speeds.

Similar to tuning these... my stock 2wd Suburban and a couple others have responded well to the Highway Lean Cruise option in ECM. 15% on mine consistently for years. A stock height and tire 4x4 Suburban shows about half the improvement. A Blazer or Suburban lifted and big tires, whether re-geared or not, does not show any improvement and actually shows some loss as well as feeling as though it's working harder. Not that synthetic gear oil would hurt or show signs of working harder, just that I doubt you would see any MPG improvements.
 
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