1996 Buick Roadmaster wagon,
LT1 with a mild cam,
2400 stall Torque converter,
3.73 gears,
Eaton posi,
4L60E tranny,
245/50/17 tires

I don't like 3.73 gears, the RPMs are too high on the highway and my MPG is not that good. So I want to switch to 3.23 gears.
I once had 3.23 gears with a stock L05 and rather liked it, it was snappy in town while still offering enough top end speed.

Also had 2.93 gears and didn't like them, too high a gear, terrible in the city even with LT1. They did however get OK MPG on the highway.

Realistically, not liking 3.73, my choice is between 3.23 and 3.42. I estimate by going to 3.23, I should get + 2-3MPG. I looked at the gear calculators and by going from 3.73 to 3.23 my RPMs should lower by 300 at 70 and end up at 2,000 at that typical highway speed. Am I correct in assuming that this will mean better MPG? Problem is, I am not really sure of my cam specs and what RPMs it likes, the PO put it in but as far as I can tell, it's a mild cam. It idles just like a stock engine. I did talk to the PO and he OKed the 3.23 swap but I just want to be certain.

I do suspect that going taller than 3.23 will actually hurt my MPG, especially in the city as I might be working outside the power band of the engine/cam. 3.23 seems to fall right in the middle between 2.93 which I found too tall and 3.73 which I find too low.

3.73 is fast as h3ll in the city and up to about 50mph but lacks top end speed. And it's not just the MPG but also the engine is too noisy for my taste. Actually, that's not exactly true, 3.73 can go as fast as any other common gear, it's just that the RPMs get a bit crazy if you push it. In my experience, with 3.73, MPG drops like a rock in the 70-80 MPH range.

The question that I have is would the 2400 stall play OK with the 3.23 gears?

It needs to lockup. This is done via PCM programming I understand. Also at what speed does the 4L60E shift into overdrive in my case? Am I going to be OK with 3.23 gears and not have it lug at any point?

 

You'll be fine I had the same on my 92 Z28. The 3:23 gears and a 2400 stall. It all worked fine.

 

Thanks for the info.

I finally got the specs for the Cam and the Torque Converter, looks like 3.23 should work nicely with this setup:

Competition Cams Comp cam LT-1 LT-4 Chevy 93-96

* Application 1993-1996 Chevy 350 LT-1 and LT-4 engines
* Power Range 1000-5000 RPM
* Idle Quality/special requirements-Best for original LT1 with stock computers
* Valve Lift 500/510
* Adv Duration 266/276
* Duration @.050 210/220
* Lobe Centerline 114


TC:

GM Big Shot 12LS
This converter is primarily used in Street Rods that are slightly modified and always street driven. The Big Shot 12LS is an excellent converter for long distance cruising with mild performance increases, good lockup, and minimal MPG loss. This slightly higher than stock converter produces good idling with mild street rod designed cam shafts. Rear ratios should be in the range of 3.23 to 3.73.
Stall speed range: 2000-2400 rpms.

 

3.23s are excellent compromise gears IMO.

 

Who got the best 3.23 gears, AAM or Motive?

Where can I order them and what are all the parts I need? I know I need the gears, the ABS reluctor, what else?

I already have a new (or rebuilt Eaton posi).

 

AAM are stock GM gears, cut to be quiet but not super strong. Motive has a blue box and an orange box. I have had great success learning to set up quiet rear ends using their blue box "stock" gears. Their orange "performance" gears tend to be a bit noisier IMO. You can find stock used GM 3.23 gears out of the auto cars that got them stock like mine did.

 

i have some 3.23's out of my car. you can have them free if youd like. just pay shipping.

 

Thanks for the feedback, everyone -


AAM are stock GM gears, cut to be quiet but not super strong.

I am not sure I need strong gears, as I am not really racing or anything, just a nice daily driver, that's all it is.