Need rearend opinions/suggestions/help please.

[Old Fart]

I don't mean to be a pain in the rear so please bear with me 'cause I'm still learning much about my car. If you have any suggestions, could you phrase it in a way I can understand. I have a '93 Z28 and am slowly rebuilding. It runs fine but the rearend is leaking a bit. So what to do...? I believe it is 3.23 and someone explained to me that that means the drive shaft spins 3.23 times in order to make the rear wheels turn once. If the car is geared higher (maybe 3.90) then I would have more power on the low end. I want quick take-off's. I don't care if the care only tops out at 120mph. I'm not gonna drive it that fast anyhow. I also plan on putting in weld in sub frame connectors. But any suggestions as to what to do with the rear end would be appreciated.

My cousin told me to go with 3.90 and I would need a new bearing spline kit I think he called it. Should I just replace what needs to be replaced or spend the bucks and get a whole new rear end. I know that would be costly but if what I have isn't in bad shape, should I just get new gears and whatever else is needed to stop the leaking. Someone posted about this: http://www.strangeengineering.net/ne...earendAD1.html so what would this do for my car. Please keep in mind that I'm not really a track person. I want the car faster on the take off but still needs to be a nice street car and something that will go down the highway nice.

And what is the difference between a 10 bolt and a 12 bolt besides two bolts? What would that do to the rearend? And is Strange better than Moser or are they both about the same? Pros/Cons?

[WMCCjames]

If I rememeber correctly, you have a 6 speed so you can get away with a 3.90 or 4.10 rear gear and still get decent gas milage on the highway. Since you want a really snappy low end take off I would do the 4.10's

10 bolts are inherently weak because of thier physical size. Only so much strength you can put into a small package. 12 bolts are much larger and therefor stronger...it really has nothing to do with the amount of bolts per say. The 12 bolt just has a larger ring gear so it has more bolts to hold it to the diff case.

As far as the difference between Strange and Moser....not too much, only Moser customer service has notoriously been very poor.

Seeing how you are not going to be going to the track and beating on the car much, I would opt to put in a 4.10 gearset into your 10 bolt along with a complete rebuild kit. Throw a new cover girdle on it and call it a day. You could easily get all that done for under a grand vs. spending $2500 on a new 12 bolt.

[JoeliusZ28]

Since you have a 93, it would be a good idea to verify what gear ratio you have just to be sure.... because if you have a 2.73, you have kind of an oddball transmission (with a really short first gear) that would make 1st gear worthless with anything that big.

the 3.90 is a good choice, it would be my preferred gear.

[ITSSLOW]

I plan on doing 3.90's eventually in my car. They will be put in just to say I've geared it. They won't last long. I'll be putting my 12 bolt in before I even build my engine....damn weak 10 bolts

[96mikez28]

3.90's would be pretty steep for an auto, 3.73's would be a better choice

[1BADAIR]

3.73 for auto's and 4.10 for 6 speeds.
9 inch for 6 speeds and 12 bolt for auto's.
The moser torque arm bracket has TA retention issues cause it uses 4 short bolts unlike the 2 long bolts that stock and strange uses

[DETROITMUSCLE]

honestly if you want the car to take off fast the best thing is gonna be a good Drag radial, peroid. A steeper gear will only make you spin more on launching and spinning isn't gonna make your get out of the hole any faster. If your gonna swap gears you might as well upgrade to a 12 bolt or 9" because with a good tire will strain on the shitty 10 bolt and could potentially break it. Just some things to toss around.

[Old Fart]

Since you have a 93, it would be a good idea to verify what gear ratio you have just to be sure.... because if you have a 2.73, you have kind of an oddball transmission (with a really short first gear) that would make 1st gear worthless with anything that big.

the 3.90 is a good choice, it would be my preferred gear.

onestly if you want the car to take off fast the best thing is gonna be a good Drag radial, peroid. A steeper gear will only make you spin more on launching and spinning isn't gonna make your get out of the hole any faster. If your gonna swap gears you might as well upgrade to a 12 bolt or 9" because with a good tire will strain on the shitty 10 bolt and could potentially break it. Just some things to toss around.

How do I verify what gear ratio I already have? Do I take my vin number to a local chevy dealer. But then again, I really don't have any idea what was done to the care before my friend bought it. Far as I know, the rearend is stock. I do know that the guy I bought the care from had a brand new (NOT rebuilt) transmission put in it. He said it was the same transmission that the car originally had. A GM tranny. I don't know if this makes a difference or not. And what is there besides a 10 or 12 bolt? Someone mentioned a 9". What is a 9"? Would that be what comes stock on these cars?

Seeing how you are not going to be going to the track and beating on the car much, I would opt to put in a 4.10 gearset into your 10 bolt along with a complete rebuild kit. Throw a new cover girdle on it and call it a day. You could easily get all that done for under a grand vs. spending $2500 on a new 12 bolt.

Where is a good place to get a rebuild kit and is any brand better than any other? Sounds like strange is maybe a better bet than Moser.



I really appreciate you guys taking the time to help me out.

[Lucky SOB]

a 9" is a STRONG ford rear end. very popular.

your car should have a ten bolt.

you can check what your gear ratio is by marking a spot on the driveshaft and then on the rear end. spin your rear wheel around one time exactly while someone else counts how many times the drive shaft spins. If it appears to spin roughly 3.23 times around you have a 3.23 gear ratio.

hope this clarifies things!

[JoeliusZ28]

How do I verify what gear ratio I already have? Do I take my vin number to a local chevy dealer. But then again, I really don't have any idea what was done to the care before my friend bought it. Far as I know, the rearend is stock. I do know that the guy I bought the care from had a brand new (NOT rebuilt) transmission put in it. He said it was the same transmission that the car originally had. A GM tranny. I don't know if this makes a difference or not. And what is there besides a 10 or 12 bolt? Someone mentioned a 9". What is a 9"? Would that be what comes stock on these cars?

the difference it makes is because its in 93... the gear ratios also affect the transmission ratios in just that specific year. 94-02 cars all have the same transmission ratios, so its easy to generalize whats best for them. '93 transmissions were different, and i believe there were 2 or 3 that could be had. if you have a 3.23 rear end, you should have the better transmission. The gear code can be found in your glove box.

[phoenix_rising]

I would suggest you get either 3.73s for fuel economy and a power boost or 4.11s. I read that 4.10s are great but they can be prone to failure whereas 4.11s are better. You might want to double check, but I would do so if I were you. Also, you should get new seals and the Purple gear lube. That will remedy the leaks and by changing the fluid you can prolong the life of your rear end. Also, since you will be taking the rear cover off, pick up a TA performance brand cover. It will help lend a little more rigidity to the rear.

Oh and do not forget to have your speedo recalibrated since the new gear ratio will throw off the accuracy of your speedometer, not good for speeding tickets. LOL.

[Old Fart]

The gear code can be found in your glove box.

Oops! I put in a new glove box and do not have the old one.

Oh and do not forget to have your speedo recalibrated since the new gear ratio will throw off the accuracy of your speedometer, not good for speeding tickets. LOL.

It's already off. The car runs about 3-4 less than what the speedo reads.

Thanks for all the help guys.

[1BADAIR]

my code sheet is on the drivers door not the glove box

[JoeliusZ28]

Oops! I put in a new glove box and do not have the old one.

well then i would say your only option to verify it then is to do the turn test. when the car is on hoist or jacks, you put a mark on the driveshaft and a mark on the tire... and count the DS revolutions made to turn the tire once.

it just depends how fussy you are. If you are 90% sure you have a 3.23, and you want to just throw in a new gearset to be done with it, the world wont be crashing to halt. The worst case scenario is that it will be overgeared, which it sounds like you would enjoy anyway

[DanO]

hmm i like 3.42's