Identifying a Rear from the outside

[84GNwith87eng]

Ok, if your RPO does not reflect G80, how can you tell by looking at the casing of the rear if it is indeed posi?

I want to make sure I have 3.42 gears and not an open rear.

Thanks

 

[83ttypecooled]

posi

Hi,
Jack up the rear end of the car, try to turn the wheels by hand, in neutral, if both turn in the same direction, you have a posi rear axle. If the wheels turn in opposite directions, it is an open rear end. I believe about 75% of '84s had posi rear ends.

 

[Larry Smith]

Jack the car up. Get both rear wheels off the ground. (Use jack stands for safety) Put the car in neutral. Spin a rear tire. If both tires spin in the same direction, it's a posi. If one tire goes backwards it isn't.
Larry

 

[Larry Smith]

Wow! Same exact timing!

 

[84GNwith87eng]

Thanks people, much appreciated!

 

[dwall]

Posi thinking!

Posi working perfectly betweeen 83Ttype & Larry...lol....

Any way to tell from outside what the gears are in that posi? My 3.42 was supposedly swapped out by dealer right after delivery to first owner... but I have no knowledge of what was put in?
dwall

 

[VadersV6]

My pricey "authentic GN rear end", that replaced the 7.5 rear that was in my car, has one wheel that spins the other direction, lol.
The fun never ends.....

 

[84GNwith87eng]

I guess after I go to work, I'll bring it to my local shop and give it the true test....something tells me I'm going to be dissapointed...

 

[DissT]

My pricey "authentic GN rear end", that replaced the 7.5 rear that was in my car, has one wheel that spins the other direction, lol.
The fun never ends.....

Man you have had nothing but let downs with that car huh? I feel for ya but a good inspection would of alleviated some of those headaches, some. Hate getting lied to personally and probably wouldn't have taken it as lightly as you have.

"Thread hijack officially over since the question has already been answered"

 

[rodman99999]

It doesn't really prove anything one way or the other, but: If it hasn't been opened for service, it may still have the, "posi fluid only" tag still on it(hanging on one of the cover bolts). I suppose someone could add one to an open rear end, if they were crooked enough. I doubt most would bother. Jacking and spinning would still be the test, then doing a burn-out to see if it's working right.

 

[ijames]

While you have it jacked up with the rear wheels off the ground, watch the driveshaft and count how many times it goes around to make the wheels spin 10 times. Divide the the driveshaft revs by the wheel revs (10) to get the rear axle ratio. For 3.42 gears the driveshaft should spin 34.2 times for every 10 times the wheels go around (3.73's would be 37.3 times, etc.) If you don't have a posi, keep one wheel on the ground and I think that doubles the number of driveshaft revs (may half it, but it will be obvious either way since you would know if you had 6.84 or 1.71 gears ).

 

[buickbert]

here is another easy way, press the brake pedal to the floor, and repeat with the gas pedal. my thinking is two tire marks=posi, one=open :biggrin:

buickbert