Hi everyone i dont really know much about differentials or transmissions...im going to pick up a differential tomorrow and thy are supposed 410s im taking the whole differential....my question is what will hapen if i just swap my differentals out....currently my differential is a 10 bolt posi with 342 gears what will happen if i just drop this one im going to get in?

 

If you dont know much about differentials then i wouldnt do this. The rear is a fairly touch thing to work on and if not shimmed properly will do things like whine or fail prematurely. Also you can install 4.10 but just because its a 4.10 dosnt mean you can install it into your rear depends on what thoes gears came out of.

 

Assuming you're talking about swapping the entire rear axle assembly, it should bolt right in. In a best case scenario your speedometer isn't going to be accurate anymore, at highway speeds your engine will be turning higher RPM, and your gas mileage will probably go in the toilet. Since 4.10's didn't come stock in these cars, there's the possibility the gears weren't set up right, in which case they could whine or worse yet slowly destroy themselves. Also keep in mind it's not uncommon for the suspension bolts to rust solid into the steel sleeves at the center of the rubber bushings, making the bolts difficult to remove. It could be easy as pie, or a total pain in the *** nightmare, but you won't know until you do it. Personally 4.10's are overkill on the street, and a bad idea with a 700R4. But that's just my opinion.

 

yes im talking about the whole differental...well i was but i just got a deal ima buy the whole car for160 bucks so i wont need to drop the rear end...and the guy said thy are 410s thats why im asking im going to pop the cover open to find out for sure if thy are...u think i can just use the posi and put new gears in it it is coming off another 87 iroc

 

Why's that?
I would think a 700r4 would be a better choice, since it has OD and a lock-up converter.

 

Because it's a bad combination? Like everything else the gears need to be matched to the car. The 700R4's .70 OD will reduce the RPM over a 1:1 transmission, but you'll still be in the 3k rpm range at 75mph. Factor in the ridiculous first gear in the 700R4 with 4.10 gears, and TPI torque and you've got a recipe for no traction. Try to fight it with sticky tires and you'll scatter that 10 bolt all over the road. Even if you do get it to hook up, you're going to run a TPI engine right out of it's power band. Assuming everything goes as good as possible, it'll probably run slower times then if it had stock 3.23 or 3.42 gears. But hey, that's just my opinion.

 

Actually, according to the calculator provided by TGO, he would be at about 2800 RPM at 75 mph, changing a little with tire size. That would be fine to me, as the fastest speed traffic ever flows at on most freeways around here is about 65 (I5 seems to go faster though...), which would be 2450ish RPM.
I'm sure the TPI motors make great torque, but I know that it isn't some ridiculous amount of power that you can never get traction on the street. Traction might be limited with stock tires, but it is anyways, right? I know that no one agrees on how much power a 10-bolt can handle, but I doubt that even with slicks, maybe even with a few more HP than stock, that the 10-bolt will break.
I understand you're trying to give cautious advice, but I think you're being overly pessimistic.