Khamaro

Hi guys I’m a noobie looking for some expert opinions if possible (yes I’ve done lots of searching but I want to double check everything before I jump in to this)
I got a ’91 z28 305, I try to do most of the “wrenching” myself and learn as I go. I want to swap the gears but this is way beyond my capabilities. So I found a mechanic that will do it for around $300 but his quote on parts was a bit expensive, so I want to order everything myself from jegs or summit. He is okay with me bringing my own parts, I just have the following questions:
1. He said if I’m swapping gears I should replace all the seals, etc. too. This makes sense to me, but is he just trying to rip me off or is it worth doing?
2. So going by the RPO code in the glove box, it looks like I have 2.73 gears in there right now. If this is true then I must have series 2 carrier, should i double check any other way?
3. If it is series 2, can I get direct fit 3.73 gears or do I need some special adaptors or anything?
4. This is not a daily driver and I find the 2.73 really boring, is 3.73 the most "fun" option without getting too crazy?
5. Are these the correct parts I need to order?
-installation kit..
http://www.jegs.com/i/JEGS+Performan...61200/10002/-1
or
http://www.summitracing.com/parts/BC...RO&prefilter=1

-gears, is this my cheapest and correct option?
http://www.jegs.com/i/Richmond+Gear/...373TK/10002/-1

-Driven gear (do i need this for the speedo, if so which one)

-anything else i might need to order?

I appreciate all the help you guys can offer, im sorry if these questions have been asked before, I would just like the reassurance of asking myself before I go and order all this stuff.
cheers,

Khamaro

Atilla the Fun

Why put gears on your open ( non-posi ) diff? If you must, here's the cheapest correct option: http://www.summitracing.com/parts/SUM-741012/ That install kit from Jegs looks okay to me, but I'd use this: http://www.summitracing.com/parts/RAT-3000K/ If the seals at the ends of the axle tubes aren't included, get them at your local auto parts store. The pinion seal and rear cover gasket come with either install kit. You'll need to change the speedometer drive gear as well as the driven gear. You need the 15-tooth drive gear. Driven gear depends on tire size, but 44 tooth is right with 245/50R16 or 275/40R17. Good choice on the ratio. Your next mod after this will be some sort of posi, so you may as well do it now. Maybe out of the budget, but 1-wheel-peels aren't so fun after the first day. If you go ahead with this plan, you'll be stuck with only 2 choices when your funds recover: http://www.summitracing.com/parts/PWT-1931-LR/ or http://www.summitracing.com/parts/PWT-92-0776-2805/ anything else would have you paying the guy another $300. But an Eaton would make you happier in most real-world situations.

mcgarnicle

iTrader: (14)

$300 is a good price for labor
1) yes
2) you can make sure by either pulling the cover and on the gears dividing the big number by the small number, or you can estimate by counting driveshaft revolutions compared to 1 tire rotation (4 turns to 1 =4:1)
3) It's been a while since I shopped for gears, but I believe they make 3 series gears for a 2 series carrier, they're a different size so find out what carrier you have before ordering parts
4) It's an opinionated subject, but 3.73's are a good choice.
5) I didn't look

Ron U.S.M.C.

According to the OP he may be working with a 2 series carrier so unless those lockers come in a 2 series they may not work. If he has to replace the carrier and match the 28 spline axles he has than I sujest a 28 spline Eaton posi. Replacing a gear ratio without installing a posi. unit ( I can vouch for the Eaton )really does not make scene. I don't care what gear ratio you have when you punch it you still get a one wheel peal. Also I would not go through all the trouble of upgrading a differential and reinstall the weak stock cover that offers no significant support other than holding in the fluid.
Buy a L.P.W. Support cover. = http://www.jegs.com/i/L.P.W./619/301-7.5G/10002/-1
Eaton Posi. = http://www.summitracing.com/parts/ETN-19599-010/
Eaton Posi. = http://www.eaton.com/Eaton/ProductsS...als/PCT_221429
This is not a inexpencive way to go but if your going to do it then save your money and do it right the first time.

Atilla the Fun

Ron, did you even look at either link? The Lock-Right and it's smoother, higher-priced version are both conversion-style lockers. They convert the open carrier to a locking diff, without making you buy a new carrier. The Eaton and most others include a new carrier. But these are only replacing the spider gears and splined side gears, which were the same for both 2 series and 3 series, so with these lockers, it doesn't matter which you have. Notice the listings for them. 26 spline or 28 spline matters, obviously, but early 7.5" or late 7.625" also matters. And what's more, GM did 26-spline versions of the 7.625, so there are 3 versions of the LR. However, knowing the car is a '91, we know it's 7.625" 28-spline. If you can't afford the gears and the Eaton, all at once, then for some it may seem better to get the gears now and do a LR later, instead of the Eaton. Redoing it later with the Eatin would cost the OP another $300 extra, but anyone can do the LR themselves, in their driveway, with common hand tools, in a couple of hours.

Khamaro

Hey thanks for all the replies guys, really helpful info....so I have verified that it is 2.73 which makes it a 2 series carrier. It does also have factory posi because it does both wheel peel out and not one. RPO code is there for posi as well.

Anyone know how much is the speedo going to be off by?

Higher gears bring up tourque numbers and not hp numbers right, but tourque will really improve the seat of the pants feeling?

Atilla the Fun

Gears don't actually increase engine torque, but they do increase rear-wheel torque. Can't figure speedometer error without knowing what size rear tires you're using. Posi option is pretty rare in an RS, congrats on that!

Ron U.S.M.C.

I looked at the links and only noticed they were listing for 3 series carriers.Kind of through me off I guess.
Thanks for pointing that out. I have not heard allot about them so I have not suggested that style locker. I will have to do some more research on that subject. Ive just been so happy with the Eaton and the set up I'm running that I tend to forget just exactly how much it cost me to build. Saved a long time for that one.