I was thinking about stepping up my stock gears to 3.42's. Seems like thats the way to go. I've been told if i do though, its gonna really kill my mileage, and i so some driving. Any thoughts.

 

do a search... we've covered this one a few times before and there are some good posts about this one recently.

 

It varies.


If you have an automatic and you step up to say, 4.10's, you'll notice a drastic drop, and this is MOST noticeable if you're an agressive driver.

Going to a 3.42 or 3.73 on an automatic from a 2.73 won't be that bad. I have 3.42 on my Z and I get 20+ mpg when I'm cruising normally, no problems.

It's definitley a worthwhile modification; you can drop some good time off your ET, and be sure to get a positraction unit.

 

I thought about spending the money and getting the posi unit, but i figure my car's not really making the power needed that a posi is gonna really be a beneficial investment. I'm a college student, so i have to be careful as to my investments b/c of money being so tight. Thats why i was just going to do the ring and pinion swap.

 

a car always can use more gear, and it doesn't take much power to feel teh peg leg holding you back.
if you do just a gear swap you are just gonna start spinning liek mad and wish you had saved up the extra money for the posi. the swap will take the same amount of time either way.
it is the kind of thing that if you only do half of it you will get less than half of the gain from it.

later
tim

 

So is this one of those projects i should attack myself or should i leave it to my favorite mechanic. If so, how much am i looking.

 

you can do it yourself prolly. it can be a real pain to set teh pinion depth and stuff properly(sometimes they fall right in place, sometimes they fight ya)
if you have to rely on the car everyday i woudl suggest having a mechanic do it. just because you will know it is done right and it will get done quickly.
learning how to do these things is great, but learning always takes longer and you won't know if you got it right until you drive on it and it either works or makes a bunch of noises.

later
tim

 

Rhoadster-

Get the posi unit from SLP. It's the same one that goes into the 93' and up F-bodies.....or so I've read. It's on sale for $85...which is an OUTSTANDING price for a posi unit; compared to the $300+ you'll drop on anything else.

 

I agree. It's a great value for third gen build ups.


As for gearing, I suggest you go to 3.73.

 

I have 3.73's in my garage, and I am REAL hesitant to put them in. My car's 5spd, so it really wont KILL my gas milage, but it will probably hurt a little bit, no?

Anyway, i have a whole new rear, casing and all. Install should be easy (i am praying), but does anyone have any tips or pointers for me? There's a slight, and i mean slight, chance of me attempting the rear this week. By the way, i am going 2.73 peg to 3.73 posi, and keeping drum to drum.

This is my daily driver, how long should this take?

Z

 

Its a good deat. Went from 3.08 open to 3.42 posi and its the best mod i made so far. I got GM Motive Performance Gears from Gearsareus, and the SLP posi and everything matched with the carriers and all. It is the same unit they use in the new z28s and trans am ( i think also)

For fuel milege, i havent noticed a difference. I just keep it in a higher gear when i drive.
~Tim

 

The SLP posi unit that is supposedly on sale for 85 bucks.....will it fit on a 91 or is it only for 93 and newer? If it will fit, how strong is it?

 

Yes it will fit a 91', or so I've read.(that's my disclaimer) The only thing you need to do is make sure you go with 3.23 gears or higher 'cause it is a 3 series carrier. Those are the gears that I'm going with, because I want a little umph, but since it's a daily driver and I do occasionally go on long trips, I'm keeping it modest.

The SLP Zexel-Torsen posi unit is an O.E.M. style, so if it's good enough for the new Z's w/ all the horsepower they're making, it should be good enough for my LO3.

Somebody back me up here, or correct me if I'm wrong.

By the way...I'm using Richmond Gears 3.23s (p/n 49-0044-1) for $190 from Summit in case you want the same thing.

 

The SLP's are take offs. They remove them and install a stronger unit when they 'upgrade' the cars. They are fine for everyday street cars.

 

This may sound trivial but don't forget to change your speedo gears or your gas milage won't change a bit. LOL
Friend of mine swaped from 2.73 to 3.42's and thougt he picked up 1 mpg but ended up he was still using the same spedo gears so it was way off. I think he lost 4 mpg on the highway and nothin around town.....once he fixed his speedo, what a dumb @$$

 

i got no official exact numbers but not really any change once i stopped flooring it from light to light. i got 7-9 mpg for the first couple weeks after the gear swap

 

My car got 28-30 mpg on the highway with cruise set at 72 with the 2.73. Now with the 3.42 with cruise set at 72 on the same road yields 26-27mpg. I also added headers and catback at the same time as posi. So I had a HUGE performance increase when I first drove it. Seems dog slow now due to recently acquiring a 99 Trans-am.