Those Running 3.73 And a TF w/ LockUp.. What's your highway Driving Like?

MopaR&D said
junkyardhero said

to be fair, i was a lot younger then. but i still wouldn't hesitate to get in the warhorse and do a california turnaround to pretty much any NA point today. currently the tires are 26.5 so it brings the R's down to a "reasonable" level. i'm not saying it's perfect, but it's about the best compromise. also, i don't care about laying rubber, ET & trap speed or trying to hustle some crap can one stop light to the next on friday night.

3.55's with 25" tall tires was a level of: i can stand this for about 2.5hrs, but super fun in town with a deep 1st 4spd.

anyway, the 46 has the same gear spread as a 727 and the OD is .69 so you'll likely want something in the 3.9X~4.1X ratio in that a 4.1X would effectively become 2.8X at cruise.

a 3.7X with the right tires might put the cruise RPM in the 1800~2200 sweet spot for a G3 hemi tho.

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Maybe I'm using the calculator wrong.. I'm coming up with right around 2k at 70mph with a 46RH and 3.08s at 70mph.. 1500 at 55. 3.73 will raise those RPMs by 300. Kind of a double edged sword that I'm playing with here. If I do go to 3.08, chances are that I'll want to regear if I end up going with the 46.. 8Hp might like it. I guess I'll have the gears on the shelf if I do go 46

Been playing with this.. has some trans options preloaded
Gear Ratio Calculator

MopaR&D said
DionR said

Just something to think about, but the later model cars with an 8HP run a 3.06 for the performance ratio and that is with an almost 29" tall tire. Those 8HP's have some really deep first gears and (I don't think) work well with the normal idea of a performance ratio. I think I settled on a 2.94 with a 26" tire when I was looking at doing one. A 3.08 with a 26" tire might work, but seems like the 3.2x ratio was actually starting to get too deep.

I guess the issue is even the computer can't keep up and shift fast enough when the rear gear get's too deep, and the cars hit the rev limiter sometimes. Plus with a 4.70 1st and 3.2x gears it is like a 727 and 6.20 setup. Might as well not even use first, probably shifts into second in the first 10 feet.

Doesn't really matter now, but maybe it is something to factor in if you do look at an 8 speed later.

Edit - I guess you have an 8 speed and 3.55's so you have probably thought about this some already. Nevermind. :D

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Dude, I always love reading your responses.. your OCD/ADHD just shines through as you try to help problem solve. Always makes a guy think.. regardless of what they have, what their experience is or whatever.

You are correct.. I have the 8 with 3.55s and first gear is pretty worthless. I can bounce off the rev limiter through about 5 gears, pretty damn quick! But it is fun when the tires chirp in town after 10 or 20 feet from a stop, with very little to no effort lol. I don't remember what my tire height is on Hoopty but the 55s are pretty sweet for every other gear and on the highway but it can be a bit aggressive on a kick down. I may have to keep an eye out for a 3.08 or 2.94 center section for Hoop.. It's an open diff now, so I'd settle for another open.. Thing gets stupid AF when both tires decide to spin! I really never even thought about doing it.. even knowing the LX cars are 3.08

MopaR&D said
MopaR&D said

2.74 x 3.08 = 8.44
2.74 x 3.27 = 8.96
2.74 x 3.55 = 9.73
2.74 x 3.73 = 10.22

2.54 x 3.08 = 7.82
2.54 x 3.27 = 8.31
2.54 x 3.55 = 9.07
2.54 x 3.73 = 9.14

I realized since you have a lockup 904 you have a lower 1st gear than an earlier non-lockup 904 or 727 (2.74:1 1st vs. 2.54:1). Above shows some quick math for the starting ratio. General consensus is a 3.2x final drive ratio is the ideal compromise gear on muscle-era cars with the taller 1st gear autos but with your lockup 904 your starting ratio is actually a tad deeper than that with 3.08 in the rear end. The lower 1st gear basically makes the starting ratio the same as one step "up" in final drive ratio. With that in mind, I'd go with 3.08 in a heartbeat. That will also match up well with an 8-speed down the road as @DionR pointed out. Not to mention doing ring and pinion changes in an 8.8" isn't as easy as in an 8 3/4" with its dropout center section so picking the right ratio the first time will save a good amount of work late

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After some reading, my 904 is pre 80. That means that my 904 gears are 2.45/1.45/1. In 1980 they changed to 2.74/1.54/1. I'm staring to lean towards the 3.08 set but how much will the 2.54 come into play? The way I'm looking at it now is the 3.08 will be a nice gear for the open road plus if I go 8HP, It'll be fine there too. If I go 46, I'm probably gonna have to go back to the 3.73 regardless. But I'll at least try the 3.08s before swapping back.