gear selection for 3 speed auto

[G_Body_Enthusiast]

currently i have a th350 in my car and while i want to put in an OD i'm looking at keeping the costs down on drive train performance, at least in this regard. it is backed up with a 2.41 gear which i cannot stand. i'm not expecting hard launches but when i press the go pedal i want to feel the car move, not think about moving and then moving slowly up to speed. i dont want high RPMs but without an OD for the moment i'll have to live with it.

but here's what i figured out math wise. at 40 MPH RPM is 1200 with the 2.41 gear, 1600 with a 3.23 gear and 1700 with a 3.42 gear. maybe the 3.42 gear is a bit much but i'm not sure. at 60 MPH the RPM with 3.42 is 2600, the 2.41 is 1800.

i dont feel the gear is matching the power curve of the engine, such as it is for a buick V6. one person described my operating RPM to that of a tractor and i'd agree.

so how much is too much? i'm guessing 3.73 is too much and 3.42 is a judgement call. i'm leaning towards a 3.08 or 3.23 gear. i suspect if i went any higher than those i'd be unhappy with the RPM.

with the current first gear ratio and the rear gear i barely get over 6.0 when multiplied, that's shameful. with a 3.08 gear i get 7.7, 1.7 more, though far from an ideal 9:1 for street performance. the 3.23 gear puts me at 8.1 which is good and healthy IMO.

if it was your car, not a daily driver, the use of the car being for street/strip purposes (mostly street) what gear would you choose? i already plan on yanking the engine for sure but the OD transmission is more of an option now since i wont be using the car as a daily driver any more so i dont necessarily need the OD gear but it is nice to have one i admit.

 

[Peter]

i think the ideal gear is the 3.23 or the 3.42, i have OD and would go to 3.73 if i found a good deal but wouldn't go looking for it. i dont drive on the highway a hell of a lot but i would like to hang over 60 mph every once in a while. i would look at the 3.43 and 3.23 and just go for which ever one you find the right deal on unless your planning on just buy eaton or something then it is a bit of a tough choice.

i have 2.41 now and my 350 can still single wheel peel as long as it wants to but the travel up to 40 is a bit weird, to get to my answer i would choose 3.43 with both the th350 or the 200-4r.

 

[Oldsmoletick]

I have 3.73's with my th350 and while it's kinda fun, I hate it for any type of travel longer than a half hour. I keep the car around 50-55 mph for fear of over revving (keep in mind this is a stock bottomed Olds 350). Part of this is due to my short 26" tires though. I would pick 3.42, you mention you want to eventually do an OD anyway, so why pick too high (numerically low) gear, and have to shell out the cash to regear it over again. You can run a taller tire with the 3.42 and most likely have a nice cruiser, with some pep, that won't scare you to go over 55 for any length of time :lol: .

 

[Longroof79]

I've been using 3.08 gears with my TH350. I do have in mind to replace the trans with a 200-4R, in which I would change the gears back to 3.42's.
It depends on how you use your car. Does it see alot of highway cruising? Alittle highway and more city use?
I think the 3.08's are a good all around gear for highway and around town use. With 26" tires, the RPM's would be around 3100-3200 @80 mph. With 27.5" (70 series tires) 2800-3000 rpm @ 80mph.
Around town, the 3.08 gears are alittle sluggish. It's a happy medium, considering my use of the car. Well until I put an OD trans in it.

 

[Phoenyx]

My Malibu has a 3 speed and 24.5" tires. I have 3.73s in the rear. And I'm very happy with them. I admit the gears suck for highway trips. But as far as in town, I love them. I'm actually debating on going with 4.11s for my next rear.

 

[jrm81bu]

I voted for 3.08's. That was my best compromise ratio before my o/d. It also has the benefit of fitting on your existing carrier, helping to keep costs down.
However, you said not a daily driver, in that case I would prolly go 3.23's, just not sure if it's worth the extra price for such a small difference in gearing.

 

[patmckinneyracing]

I voted on the 3.42, not simply because its the biggest. I was happy with my th350 and 3.73 gears, up until I had to drive long distance, which most places I have to go to involved highway driving since it is San Antonio and all. Since I was running a 215/60/15 tire on all corners, my rpms would be 4000 at 70mph. But if I had 3.42 gears, and my driveshaft didn't snap and destroy my th350, I would have kept my TH350 and probably loved it. My rule is 3.42 or less for 3 speed, 3.73 and higher for OD trans. But since I don't plan on swapping gears, I'm in the process of putting in my 700r4.

 

[pontiacgp]

I'm running the 3.08 with a t5 wc which has a first gear of 2.76 and it launches pretty good....

 

[RockSS]

Here's a thought for you the OD transmission either 1 2004r or 7004r has a lower first gear so if u went with say (my suggestion) 3.23 3.42 the turbo 350 would be good with out over rev. on hiway (wouldn't be just putting either) but if you where to decide to go OD it will feel quicker because of the higher 1 gear 2.73 on 200 3.06 on 700. I have 3.73 in 2 cars elky with a 350 lots of fun around town and my 87 ss w/OD I kinda feel like its still just a little much for the hiway but It's YOUR car and everybody has different preferences. 65 mph 3150 rpm 26" tire 3.73 350tranny. play with some of these you'll get an Idea


http://www.wallaceracing.com/Calculators.htm

 

[RockSS]

Sorry I know someone will corect me 2004r first gear is 2.76 I made a typo and you can buy series 3 gears for series 2 carriers I have a set of 4.10 richmond gears for a factory 2.41 limited slip rear but i decided thats a little too high for me but maybe not now that I have multiple toys