[SunnyZ28]

What would a suitable transmission be for a 3.73 rear end?
I was reading that 3.73 is kind of in the middle, and I am not sure which would be faster/better for the car

 

[Fred Ficarra]

Ya gotta tell us stuff about the car and what you'll be wanting to do with it.

 

[SunnyZ28]

Well at the moment, the motor is FUBAR'd, Im looking at a GM crate motor, high 300's low 400's HP. I want to drive the car around cruising, but I also want to once in a while take it to the track. It will be taking the highway sometimes, but the final drive on both a close and a wide 4 speed is 1:1, so it shouldnt be any different right?
It's a 69, 4 speed [right now] but the trans is starting to go to, so I want to replace it.. so I was looking at a new Muncie either close/wide ratio.

What else do you need to know?

 

[William]

The main consideration will be where the engine you chose likes to produce power.

An engine with a broad power band [ex: 300/350] peaks at 5000-5500 rpm and has good power from 3000-5500. This engine has good low-speed torque and doesn't need high numeric gear ratios to move from rest. A wide-ratio trans is the choice here because with each shift the engine rpm stays in the power band. But due to the limited rpm potential a high numeric rear axle ratio would limit top speed.

An engine with higher power but narrower power band [ex: 290/302] peaks around 6500 rpm but due to the larger ports, carb, cam timing, does not produce good low rpm power. This engine has poor low-speed torque and needs higher numeric ratios to move from rest. A close-ratio trans is the choice here to limit how far down the power band engine rpm drops with each shift. An engine with higher rpm potential needs a higher numeric axle ratio for max performance.

I have had Z/28s with both trans and it depends on how you will mostly drive the car. A wide provides more total 1st gear for easier launch [2.52 x 3.73 = 9.4] but under hard acceleration shifting at 6500 rpm the 3-4 shift drops the rpms to 4,400 and it feels like a stiff headwind. The same shift in a close drops rpm only to 5,100.

 

[Fred Ficarra]

Sunny, do we have experts here or WHAT!?

 

[deerhunter]

Or you could go with a TKO 600 and have all of the bases covered.

 

[SunnyZ28]

Or you could go with a TKO 600 and have all of the bases covered.

is it a direct bolt in?


and Fred, yeah we do. Thanks for your help guys!

William: The engine will have decent low-end torque, so it sounds like a wide-ratio trans is what I would need?

 

[William]

Yup, most engines are fine with the wide.

Another point: a wide with 3.55s has virtually the same total 1st gear [2.52 x 3.55 = 8.95] as a close with 4.10s [2.20 x 4.10 = 9.02]. 3.73s can be a bit busy for extended high-speed driving.

 

[Straight-line-69]

With the wide power bands (useable rpms) of the street engines we're building today, I think a wide ratio is the call. My opinion.