3.73'3 w/ a 229

[Monte83]

Would a 3.73 rear make a 229 scream? I think the gears now are 2.29's, but I might be getting a new rearend with a "peg-leg" setup with 3.73's.
The reason for the new rear is rust..the backing plates are pretty much gone and the spring cups are on their way out.

 

[Garage Hound]

"Scream" might be a bit overstated, but any rearend upgrade makes a difference in ET regardless of engine. The bigger issue is the increased RPM stress put on an engine when going up in gear ratio. The higher the ratio = more RPM = the stronger the engine needs to be.

 

[Monte83]

This is just a daily driver.
How much of an affect will it have on rpm and fuel mileage.

 

[Garage Hound]

I used an RPM calculator I found the web, and the following is what calculated.

2.29 gear ratio
27" tire (I guessed on this, since I don't know what you have)
65 MPH
1852 RPM with 1-1 overdrive

Exact same setup as above, but with a 3.73 raises the RPM to 3017.

 

[mhamilton]

I can't imagine it doing much of anything for the 229... there's just no power past 2500 rpm, that engine falls flat on its face (in the stock configuration). Was designed for low end torque, not high rpm hp. And for a driver, forget about economy. Might as well just put your existing gear in 2nd and drive like that (1.5 * 2.4 = 3.6 final ratio, equivalent to a 3.6 axle in 3rd gear)

It would be interesting to hear the results if you swap the axle, but the few times I've pushed mine through the rpms, the results were disappointing.

 

[larryg]

I might be sticking a 3.73 in mine as well, but its the 231. I may have to calm down on the highway but at least kids on bicycles wont beat me off a light! :mrgreen:

 

[Anonymous]

I can't imagine it doing much of anything for the 229... there's just no power past 2500 rpm, that engine falls flat on its face (in the stock configuration).

Not trying to hijack this post...but would a different cam change this problem of the power dropping off at 2500 rpm?

Trickbu

 

[mhamilton]

Of course, that's basically the only difference between the 350 GM put in an Impala verses the Corvette. The stock cam was designed to produce low end torque, for use with the high axle ratios and heavy cars. Also was designed to control emissions (using technology at the time), so it's less than ideal to begin with.

But I still wouldn't expect the 229 to be that happy at high RPM, just as the 305 isn't really a high rever. The smaller bore and valves will limit breathing. It can be fixed, but never really as good as the larger bore 350/4.3L. And the 229 has it's little splayed-pin semi-odd-fire crank, which isn't the strongest thing out there.

 

[purecrazy]

changing the cam, find a set of heads from an early 4.3 (85 & 86 carbed engines), valves went from 1.84/1.50 in the 3.8 vs. 1.94/1.50 in the 4.3, also the early 4.3's had 4bbl intakes and carbs that you could use on the 3.8. combine that with dual exhaust and with the 3.73 gears, there will be a noticeable power increase