What rear end oil/weight?

[milit73]

I am going to replace the oil in the rear end or add to it but what is the best oil or weight to use? Thanks 68 Superbee 383/727

 

[Hemi Rebel]

I run 75/140 synthetic in mine. course, i get it for free. if you are just topping off im sure 80/90 would be fine. anything is better than nothing for sure.

 

[67 coronet]

80/90 gear oil is stock.make sure to use a nonslip additive if you have posi.

 

[rev.ronnie]

I use Synergen Syngear II on everything. No posi additive needed. I run it in 2 Dana 60s and they love it.

 

[milit73]

no posi just a normal rear end and not sure of size as my dad blew the original years ago and did not remember what he put in so.............is there a way for me to find this out or do I have to remove it to find out? Once again thanks for all of the help guys.

 

[bigredbird]

See the chart here for visual reference on the size.

http://http://forums.moparmusclemagazine.com/70/8307903/mopar-drivetrains/chrysler-rear-end-id/

Or do you mean gearing?

 

[PurpleBeeper]

Gear Ratio

no posi just a normal rear end and not sure of size as my dad blew the original years ago and did not remember what he put in so.............is there a way for me to find this out or do I have to remove it to find out? Once again thanks for all of the help guys.

You can figure out your gear ratio by raising both tires off the ground, line up one u-joint (say, at 12 o'clock), mark one tire (say, at 12 o'clock), put the car in neutral and rotate the driveshaft one full revolution & count the number of tire rotations you get on the marked tire. There are a limited number of gear ratios available, so you can figure it out for sure.

I did this years ago on my Roadrunner since the rear end was missing the tag and the guy I bought it from said it had 3.55's in it. I had a touch over 3-1/2 tire rotations for one driveshaft rotation. I pulled the pumpkin years later and sure enough, they're 3.55's. So, this method is pretty accurate and you can definitely tell the difference between 3.23's and 3.55's which are pretty close. (3.23's would only be about 3-1/4 tire rotations)

 

[tpodwdog]

You can figure out your gear ratio by raising both tires off the ground, line up one u-joint (say, at 12 o'clock), mark one tire (say, at 12 o'clock), put the car in neutral and rotate the driveshaft one full revolution & count the number of tire rotations you get on the marked tire. There are a limited number of gear ratios available, so you can figure it out for sure.

I did this years ago on my Roadrunner since the rear end was missing the tag and the guy I bought it from said it had 3.55's in it. I had a touch over 3-1/2 tire rotations for one driveshaft rotation. I pulled the pumpkin years later and sure enough, they're 3.55's. So, this method is pretty accurate and you can definitely tell the difference between 3.23's and 3.55's which are pretty close. (3.23's would only be about 3-1/4 tire rotations)

you got that backwards....

one tire rotation....3 1/2 driveshaft rotations.= 3:55

 

[Garys1969RR]

And you said not a posi unit? In this case you only raise 1 tire, and leave the other rear tire on the ground. Rotate the wheel 2 FULL REVOLUTIONS, While an assistant counts the number of turns on the u joint. For example, my Roadrunner had an open rear end with no tag. 2 wheel turns came out to 2 3/4 U-Joint turns. It was a 2.76 ratio. Have since gone to a 3.91 Sure Grip.

 

[Garys1969RR]

Oh, and in a posi unit, or a sure grip I use 85 W 90 gear oil with the GL-5 additive. This GL-5 is a must with standard gear oil. It comes mixed in the oil already.