how to identify gear ratio and sure grip?

[moparmussel]

how do i identify gear ratio when id tag is gone on 8 3/4 rear? also,how do i identify a sure grip? thanks,mark.

[Slingshot383]

Jack the vehicle up, put jack stands under the rearend. Turn one tire, if the other tire turns the same direction it has an anti slip rear end of some style. To know it it's an Auburn or clutch style the only way is to pull the pig out. for gear ratio, count the number of turns the driveshaft does for one turn of the rear tire.

[Ray Bell]

Go back through previous threads on this subject, in one of them in the past few months I've posted pics of the different types of Sure Grip...

I think you might find it easiest if you look for 'spool' in search. Pretty sure that was part of the subject.

[moparmussel]

thanks guys,merry xmas!

[tri_power340]

someone told me while you have it jacked up have one person hold one tire and another turn the other. if if turns easily its an open rearend. if its tough its some sort of posi unit.

[rumblefish360]

#1. Jack both tires up and off the ground and use jack stands to keep'em there.
#2 turn a tire. If they both roll in the same dircetion, your sure grip equiped!

#3. get oil pan and drain rear end fluid, believe me, you need to do this because no one before you has serviced the rear end since it rolled out of the factory.

#4. Have gear oil and additive ready. 2 quarts should do ya fine. 1 additive bottle from MoPar or off the shelf at AutoZone will be fine. Have gasket and gasket scrapper ready.

#5 After fluid is drained and rear cover is off and all surfaces cleaned up and ready for re-assembly, rotate the wheel slow, look on pinion gear for the ratio stamped into the ring gear.

#6 re-assemble and fill with additive first and oil second and be happy and confident of a freshly serviced rear and known gear ratio.

#7 Pound chest proudly for doing the right and smart thing to your Mopar without taking short cuts. Smile big for the camera, say chesse. Drink fav. drink.

[72Challenger]

That's the most complete set of directions ever! Even the factory service manual leaves out step #7. Good job, Rumble!

[Cudadrag]

On the Dana the rear gear ratio are the number of teeth of the ring gear (Mine is 39) divided by the number of teeth of the pinion gear (Mine is 8) thus a gear ratio of 4.875 or 4.88s. I believe the 8 3/4 is the same. The pinion to ring gear ratio does equate approximatly to the number of pinion revolutions per each tire/wheel revolution.

[moparmussel]

thanks rumble,i was going to cheat and count turns of the drive shaft but i really like the idea of service while i have it up on stands anyway. auto cheepy zones have slip additive,any brand better than another? gear oil,90 weight?

[rumblefish360]

72Challenger, he he he, thanks.

Cudadrag, I'd count pinion teeth, but my eyes can't keep count of how many times I go around. Last time I got to 37 pinion teeth and decided if I was going to screw up this bad, there better be at least 6 bottle tops on the floor. He he he.

moparmussel, I used the Mobil sysnth gear oil, exact weight I forget. The Auto Zone gear additive was cheaper and works just fine. I have not yet noticed any one really better than the other. Key word, yet.
I used the MoPar brand and auto zone and 2 others. I forget.
The MoPar fluid was flawless, best of the bunch.

[Madman Stephan]

Okay, along the same lines, without hijacking the thread, I'm rebuilding / upgrading the rear-end (741 case, non sure-grip) of the Challenger from a 3.23 to a 3.55 and figured that, as long as I'm ordering parts for one rear-end I might as well order parts for the Charger's rear end as well. At this point, I know nothing except that it's an 8.75. So I jack up the car, take the wheels and drums off, and ask the wife to come outside and help me. She stands on the passenger side, and I'm on the driver's side. I ask her to tell me which way the hub turns (cw or ccw). So I turn mine ccw, she tells me her side is spinning cw. "Cool", I think, "I have a sure grip". So then I start turning it cw, and she tells me her side is still spinning cw. W.T.F.?!?! Then she says it start turning ccw and then it starts turning cw again, all the while I haven't switched the direction of my spinning...

So, should I get another wife?

[rumblefish360]

He he he, was the car level?

[Madman Stephan]

I tried it again, while making sure the car was level, and the same thing happened. When the driver side rotates forward, the passenger side rotates forward. When the driver side rotates backwards, the passenger side rotates forward, then stops, then goes back wards, then stops, then goes forward again. Somethings f!cked up! I'll have to assume it's a non-sure grip unit until I take it apart.

[daredevil]

Only new glasses

[daredevil]

Maybe the spider gears are changing direction in an open diff.