It's time for a gear oil change in the rears. I have always used dyno gear oil but I'm doing a lot more heavy towing now. This is a posi rear.

Three questions, will the 92 Dana possi rear work with synthetic and in fact would it be better for me to go synthetic or stay with the dyno?

If synthetic is the way to go what synthetic gear oil has proven itself to work under tough conditions?

Do I use the same weight in synthetic as I use in dyno

thanks for the help

 

I've heard guys running amsoil 80w-90 synthetic in open rears, but I don't know about how that would work with a posi and the fiction additive. I'm putting a posi in my 70 rebuild right now and I was wondering about running synthetic too.

 

I'd go with a 75/140 if I was towing alot. I like the Royal Purple Severe Gear because it already has friction modifier for the diff clutches mixed in. Been running in mine since before I bought the truck and seems fine. The only difference you'll see between the dino and synth gear oils is the synths run longer and cooler.

 

so do you add any additional friction modifier?

 

Even with the dyno oil that has the additive already in it I put it in anyway. I want to make sure there is plenty.

The big question is synthetic (much more slippery than dyno) will the clutches slip? Now that may seem like a dumb question but in my bikes that share the motor oil in the engine and the trans it says not to because the clutches will slip and you won't go anywhere.

I just want to be sure synthetic is fine in a posi rear.

thanks

 

http://www.richmondgear.com/01accessories.html#rear

does that help

 

It'll be fine with the limited slip additive.

It's probably getting close to time for a new set of clutches in that rear. If you let it go too far you'll wind up buying spider and side gears too - like I did. How much can you turn the driveshaft back and forth?

 

I'll check tomorrow but I don't think there is much more play if any than it always had. Can't swear to it now. How much am I allowed?

Hey Dave I assume the synthetics have the additives already in there right? I will probably add more anyway. Do you think 80-140 is right for heavy towing?

 

If you can get 1/4 turn out of the shaft and the rear doesn't howl, then the clutches are getting thin. On our limited slip diffs the clutches set the engagement depth of the side and spider gears, so as the clutches wear you get slack between the side and spider gears.

Don't assume anything, read the bottle. If it's in there, it will say it's in there. WhateverW-140 will be fine, different brands have a different cold weight and all of them will work fine.

 

Sounds like no problem. Thanks

 

Synthetic oil does not make the motorcycle clutches slip, I have ran synthetic oil in my bikes for many years, the friction modifiers in oil make them slip. If it states on the bottle that it is energy conservation oil then do not put it in a motorcycle as it has too much moley in the oil. Synthetic lube for the rear end is good for severe service like towing. I keep it in mine all the time.

 

The only thing is after 5-11k miles my old dodge the rear pinion seal goes out because the synthetic loosens it up. JMO Replace it before it starts leaking and your 1000 miles towing from home like I was... Its cheap from the dodge dealer and Midas or places like that do it for cheap but it isn't hard to install yourself, (just torquey as a mother ******)

 

ok thanks. Yep Synthetic is goin in mine in a few days.

 

What makes you think the oil caused your pinion seal to leak?

 

How difficult is it to replace the clutches?