how hot does a 8-3/4 rear end get?

[troy.70R/T]

I was wondering how hot an 8-3/4 rear should get? I would think I should be able to hold my hand on it after driving it for an hour. but mine is real hot. and yes it does have oil in it.

[fy469rtse]

Brand new set up ? , they will be tight, it will free up  , ? How hard a time were you giving it ,
If new think about changing fluid out soon
They do get warm , they ran coolers and lines off these to keep temps down in NASCAR

[troy.70R/T]

Yes new bearings and seals.  I did drive it somewhat hard. just hoping I have the back lash set right. I dont hear any noise except in reverse. but I am sure that little bit of noise is in the 4 speed.

[c00nhunterjoe]

Yes new bearings and seals.  I did drive it somewhat hard. just hoping I have the back lash set right. I dont hear any noise except in reverse. but I am sure that little bit of noise is in the 4 speed.

What preload did you put on the carrier bearings? What did you set the backlash at?

[fy469rtse]

they get warm anyway, they have to work hard , give it a oil flush , change, soon and make sure its got enough fluid , fill to drain hole ,

[flyinlow]

I checked the carrier of my 3.55 ratio after an hour of 70 mph diving on a summer day with a a cheap laser thermometer.   155* F.  very unpleasant to touch

[troy.70R/T]

thanks guys. I would have answered you all sooner but I dropped my phone in my dogs water dish. I bent over to pick up his water dish and it fell out of my shirt pocket and right into his water. . I cant remember what preload or what backlash I set it at. I would assume I went by the book and did whatever it told me to set it at. I have done some chevy ones and never had and  problems but then I dont remember them being that hot. I will have to change the oil and try that. maybe I can even drive it to a shop and see if they have a laser and will take the temp for me.

[fy469rtse]

Nah it's normal for them to run hot , if you had miss aligned anything it would probably wine it's head off or clunk badly when you put it into gear
It's all good from the sound of it

[troy.70R/T]

Thanks fy469rtse I feel a little better about it. I will change the oil and see if I find any metal in there. I know I am running 85W-140W should I run something heavier? would synthetic run cooler?

[flyinlow]

Ma Mopar put 80w/90 in them with no change requirements under "normal" driving.  I use 75W /90 synthetic plus suregrip additive and do change it every few years. I have only used that heavier 140 Wt. in my pick up that calls for it.


Not sure if you are aware, 8 3/4 axle wheel bearing are manually lubed. They do not get axle lube to them. They are greased by hand when you take the axles out. Owners manual never mentioned greasing them that I remember. But after 40+ years   

[troy.70R/T]

HMMMM  I will have to look into that. It has been so long I cant remembeer if I greased them or not.

[fy469rtse]

Yep the old roll them in grease in the palm of your hand , you don't have to take them right out just enough to grease bearings and pop them back in