I have a '84 Z28 with a LT1, 700r4, 245/45ZR17, and 2.73 reared gears. I'm currious if I will aquire too much of a tration problem by choosing 3.73 gears. Maybe I should choose a 3.23 ratio. I'm not building this Z to just be a 1/4 miler. I want it to be fast on the 1/4 and have a good highway speed. Has anyone experienced many ratio differences to give me some advise? Thanx, Mark.

 

The 700R4 has a first gear ratio of 3.06:1. Having that ratio is nice because you can run the 3.42 gear set and come out of the hole very strong. If you are building something to play with on the street, the 3.42s are a great all around gear. I had the 3.42s in my stock 10 bolt for 10 years with an A4 and they were great. I just switched to a 12 bolt and went with 3.73s becasue I wanted more pull on top end to match my cam's powerband. With the 12 bolt I'm not worried about breakage. The 3.42s seem to be a good strong gear for a 10 bolt...

--Alan

 

I've had 2.73's, 3.73's and 4.10's in my car. Yeah, yeah, easy on the gear swaps bud, I know!!

While there is a slight difference, there's not much difference between 3.73's/4.10's, but when you switch from 2.73's, you'll REALLY notice it off the line!! If you want to get an idea of what it'll be like on the highway, just drive your car the way it is (w/2.73's) in 3rd gear. The revs will be up there, but that's what you'll have to get used to ... they're very close to what they are in 4th gear and having 4.10's. So if you can handle that, then you know you'll be OK with 3.73's.

I don't know how much you go to the track, or if you have any times yet, but even with 4.10's, the car is still capable of hitting around ~110 mph without bumping up the rev limiter or running bigger tires, so with 3.73's, you've got that much more room to "play" (ie: nitrous). Off the line you really notice the gears though ... you get thrown back into the seat pretty hard!

Oh, and traction is not as bad (IMO) as you might expect. See my 1/4 mile times in the sig ... I got that 1.94 60' time on STREET TIRES. I even pulled a 1.92 on street tires, but didn't cut the quickest 1/4 mile run that time.

 

Thanx for the help. Withe a 2.73 to a 3.73 swap, I'm expecting to see a sec diff in my 1/4 mile time. From a 14.1 to low 13's ya'll think that accuate?

 

Nope, look at my sig. If you get a ~13.6 - 13.8 you'll be doing alright. Throw in a stall converter, even with your 2.73's, and you'll knock off a solid 1/2 second .

 

3.73s are a little tough on stock rubber with the auto. My car went from an A4/2.73 to M6/3.73, then a year later the M6 crapped out and i put the A4 back in with the 3.73s still out back. Drove it for a day or so like that, and i'll tell you what, it'll roast the tires hard in 1st gear. The 1-2 shift is quite entertaining too. Picked up a 3.23 rear end a day or so later and enjoyed that too. Not as strong off the line, but it's a little better on the hwy rpms. Still a lot better than the 2.73s. 3.73s are good if you have good tires and aren't worried about a little more cruising rpms though. i would've left the 3.73s in there if i didn't do so much interstate driving.