indirocz28

Ok- i have my 86- and it currently has a set of 3.23 gears in its stock rear..

I want to go with some lower gears, but still get decent gas mileage.. The lowest i want to go is to 3.73's..

What i need to know-
what series carrier do i have in my rear?
What differential do i have in my rear?
How does changing from say 3.23's to 3.42 or 3.73's affect the cars performance and off the line tourque?
how hard is it to swap out a ring and pinion assembly and what all will i need to get when i do the swap?

All answers are greatly appriciated. THANKS!!!!

ede

if you have a factory carrier it's a 3 series. it should be a 10 bolt from the factory, again you should get under the car and take a look. what GM did and what you have may not be the same thing. in a nut shell lower the gear the more you'll feel it pull and the less milage you have. you'd need some sort of special tool to hold the yoke, in/lb dial type torque wrench, mag base and indicator, depth mic or pinion setting gage, ft/lb torque wrench, press, bearing seperator, 0-1 mic or caliper is good to have. you'll need at a minimum the gear set new pinion nut and clush sleeve/spacer. if the bearings are questionable you'd want new bearings too. an assortment of shims is always good to have. you can buy install kits with all the hardwear you'll need. i'm suprised you didn't find all this info when you did your search. i'm thinking me and a couple of others have posted it before.

my3rdgen

I went from a 2.73 to a 3.73 and the difference was night and day. It was an awesome upgrade and well worth the money and mileage (which wasn't much) I went from around 20 to 17 on the freeway and my in town mileage did not change much if at all.

However, with the stock LG4 dropping off sharply after 4500rpm it was too steep of a gear for the LG4 if left in stock trim. But for the mildly built 355 I installed they will be perfect.

Off the line torque was greatly improved. The LG4 couldn't do a burn out with the peg-leg open rear to save its own hide. But once the posi and 3.73's were installed, I could roast the tires through first and almost all the way through second.

indirocz28

Well a buddy of mine has 4.10's, and he gets really ****ty mileage, so the lowest i want to go would be to the 3.73's.. And my 358 has a hell of a top end with the vortec heads on it and pulls strong deep into the 5 grand mark..
I think i'll say screw the 3.42's and go with the 3.73's..
Thanks both of you!!!

indirocz28

Another question- How do i know if i have a 7.5 or 8.5 rear end? And- how far will switching to 3.73's throw off my Spedometer, and how can i correct it?
Thanks again!!!

sofakingdom

iTrader: (1)

It's real simple to tell: do you have a 82-92 F-body 10-bolt? then it's a 7.5". There are no 8.5" in these cars.

indirocz28

Ok- that works, cleared that one up quick.. THANKS!

Saigon_Bob

iTrader: (2)

you can get a different speedo gear or do what i do... go with traffic... i never had a speedo so i got used to it

my3rdgen

I think it would be a good choice since, in my opinion, don't see much of a difference going from a 3.23 to a 3.42 for the cost that will be incurred.

In fact, your 3.23's with the right TC might be just fine with the 358 if you are only pulling to 5-5.5K or so. But if I have to choose between fine or fun... Fun always wins.

indirocz28

Yeah, someone said that i could put a 3800 stall in my 700 and still get about the same gas mileage probably as you do w/ the 3.23's...

but - im still thinking of the 3.73's..

Saigon_Bob

iTrader: (2)

well whats more fun... 20 mpg and 50 ft burnouts or 15 mpg and being able to light the tires for 200ft

indirocz28

Exactaly- but i also wanna be able to hook up on the track..

1991L98G92

If your speedo and odometer don't work, then you won't need to worry about the speedo gear. If your speedo & odo work, your speed will be reading faster and your mileage will click quicker. If you don't care about the number of miles on your car (I hope I don't cry when my car hits 100,000), then there's no big deal, either. But if you care about your speedo being acurate: your speedo will be off in percent. Your trans will be spinning more times to turn the wheels, thus, speed will read more. If your doing 70, and your speedo is reading 77, your off 10%. You would need 10% more teeth to slow the speed down. Your gear is 20 teeth. 10% of 20 = 2. You would need 22 teeth. If that helps any.

indirocz28

well- they work, but, does anyone make a changeover kit?