How do I identify what size rearend I have in my car (i.e. 8.5", 7.5", 7.62" etc...)?

My car is an 84 Z28 with the L69 package but no posi. It currently has the 3.73 gear in it. The rearend is out and opened so I can measure anything I need to.

Thanks for the help!

newZman

 

7.5"/7.625" 10 bolt

 

Aw, that's easy. Thanks Apeiron

 

One other, hopefully easy, question.

How do I tell whether it is a series II or series III?

 

3 series

 

Yeah that's what mine is, but how do I tell the difference between a series 2 and series 3?

I have another posi differentiel with 3.42 gears and dont know if it will drop in to my rearend.

 

From the 10 bolt sticky at top of this section:

What Carrier Do I Have?
There are two: Series II is 3.08 down, series III, 3.23 up. Steeper gears, say 3.73’s, can be swapped into a series II with gears designed for such a swap, or by purchasing a series III carrier. (This would be an appropriate time to upgrade to limited slip and 28-spline axles.)

 

I actually read that sticky and I dont think it answers my question. Please correct if I am wrong, but from what I can tell from my research is that you can pretty much put any gear ration on either series carrier providing the gear set is for that particular series.

Here's where my question is from; I have two complete rearends one is a posi rearend and the other is not. Both have drum brakes so no advantage to the swap other than the posi. I know the rearend in the car now is stock with 3.73 gears so I can assume I have the series 3 based on the above. But...

How do I tell if the posi differential is for series 3 or series 2 rearend not knowing what the stock gears were?

 

Or, can I put either series differential (carrier) in my rearend providing the gears are the correct gears for that carrier? Or do I have the deffinition of carrier wrong?

Thanks for the help?

 

You can put any series carrier in your rear with gears appropriate for that carrier.

In a series 3 carrier, you can only put series 3 gears (3.23 and numerically higher).

In a series 2 carrier, you can put:
-Series 2 gears (3.08 and numerically lower)
-Series 3 gears with a spacer (3.23 and numerically higher)
-Series 2 gears with extra thickness to allow series 3 ratios (3.23 and numerically higher)

 

Excellent!

Thank you! That answers my questions regarding my setup.

There is a measurement that can be made from the outer end of the differential to the mounting surface of the ring gear that will allow one differentiate between the two. There is a difference of about a half an inch between the series 2 and 3, the problem is I dont remember which was which or where I found that info, I thought someone here might know.

Anyone know how to tell the difference between a series 2 and series 3 carrier without the the gears being on the differential?

It's the difference between understanding what it is I am doing and doing it that way just because the book says so. Maybe not important to most.

 

Somebody has to know what the difference between the two carriers is and how to tell them apart. Basically what I hear here is that you can't tell the difference without having the stock gears on them!?

Anyone?