Forget about what you have, that's all ancient history, you are wringing that engine for what it's worth as it makes no torque. Like I said, what will be your "primary" driving situation? This dictates gear ratio once you have locked in tire diameter and transmission. Gear it too high and regardless of torque, you will be pushing the engine harder to compensate and mileage will suffer around town. Me, I'd go 3.73, certainly no lower that 3.55 but then again I ran 3.73's with a TH350 for years behind a tweaked ZZ4 and never thought twice about 75mph on the highway, all the better for roll racing too.
3.08 or 3.31 with 4L65?
- Thread starter CaliWagon83
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It also depends on your plans for tires as well. I say 3.31 especially if a taller tire is used.
I'd be shopping in the 3.23, 3.31, 3.42 neighborhood. Remember that a 4L65 has a pretty deep 1st gear. Ideal compound 1st is 10:1 (rule of thumb).
Tire height will be a big factor unless you stick to what's there. I'm at 26.4" with 3.42s and a 4L60e. I dig it, but would go a little higher if I had more power.
Seems like 3.31 might be the best overall choice, good balance of responsiveness around town and relaxed freeway cruising.
Higher as in taller (numerically smaller) or shorter (i.e. 3.73)?
Higher as in taller (numerically smaller) or shorter (i.e. 3.73)?
Yes, taller. If I had more torque, 3.23s would probably be perfect.
You also my have a slight weight problem over my crew cab.
I think you kinda answered your own question and of the 2 I would go with the 3.31 which would have you turning around 2200 @75. Since your going to be doing most of your driving around town I would personally bump up to 3.42 or 3.55 which would help get that car moving and more than likely get better fuel economy. With what you doing I wouldn't have a problem running a 7.5 rear end, but if you need to build a 7.5 it would be money better spent upgrading.
Greetings CaliWagon & all; I think you asked for opinions. I was glad to see that your prefer the 12 bolt over the 9 inch. Form my experience the extra unsprung weight of the 9 inch is NOT justified for most street driven hot rods. Sure if ya got 600 ++ Lbs Ft of torque ya go the ford route. But for under 600 Lbs Ft of torque the GM 12 bolt, 8.5 10 bolt & the 8.8 Ford are much better choice. So many guys don't give the unsprung weight enough thought. And for gears look no farther than GM engineering, as many LS 2's & LS 3's that were equipped with 4L60 & 65 E's 3.42 was the choice. If ya get too tall (3.08) with that trans the combo just doesn't seem to work well. I say that from experience as I ran a 700 R4 (same gearing as the 4 L60-65E's) with a 3.08 & the combo just didn't work well. Then switched to a 3.73, I didn't like that either, so back to the 3.42, the Sweet spot! Good luck, Ole' Bob.
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