gear selection. your opinions wanted.

[MY85pontiac]

car: 1985 Grand Prix

engine: 231 C.I. N/A Buick V6

tranny: pre 81 TH-350

present gear: 2.41 one legger


ok so my daily driver has a very weak gear and since i put this tranny in its been even slower off the line (i previously had a th-200 metric POS) and i need a real gear, not this granny gear crap and i have come up with my own formula for gear selection.

now as a rule of thumb for a "street car" (very relative term here) if you multiply your trannys first gear by whatever gear you want it to be around 9:1. for a drag car it should be around 10:1. this does NOT take into consideration OD trannys like the 200-4r (which i dont have so lets not even discuss them at this point) however i feel for a daily driver (with an emphasis on daily driver first, performance second) the number should be around 8:1. now i'm using that number because while i want to increase performance it is STILL first and foremost a daily driver so gas milage is still a consideration i must keep in mind. now i have done some things already to improve gas milage: just replaced the carb with a holley remanned dual jet (runs much smoother and has made a big difference in performance anda little in gas milage), electric fan set up (runs cooler, has more power and gas milage has made a significant improvement) and i know the gear will off set what i have already done and then some but i'm tired of everyone getting the jump on me, i'm not slower than everyone but this gear makes for crappy take offs.


now my trannys first gear is 2.52 my gear is 2.41 multiply them and you get 6.07, pretty crappy huh? multiply my trannys first gear with 3.23 gear and you get a more respectable 8.13. thats a 2.06 difference and a difference i think i would feel immediately! 3.23 is the closest gear i can find and stay above 8:1, 3.08 lowers it close to mid 7's.

now ive done some calculations and driving around below 50 MPH i wont notice much of a difference in RPM levels at cruising speeds which is good. highway driving might suck but i rarely do that now so its no big deal to me.


so does anyone agree with me? anyone have anything they want to add? think my gear selection sucks? think its still too weak? thinks its too much gear? this is very important to me because gears are not cheap and not something i can do myself. gear selection is one of the most important things we can pick for our cars, it can mean the difference between a fun car and a car you absolutely hate now (whether the gear you chose is too steep or not steep enough).

to reiterate:

2.52 x 2.41 = 6.07 (what i have presently)

2.52 x 3.23 = 8.13 (what i want and what i think the car needs)

2.52 x 3.08 = 7.76 (i think this gear is too low)

2.52 x 3.42 = 8.61 (i think this is too much gear)

 

[b4black]

The '82 GN came with the lowest ratio I know of on a NA V6 without OD - 3.23. The '82 Turbo Regal came without OD and a 3.08. Either sounds good to me.

How are you going to change the gears- junkyard gears, complete rears or aftermarket? Are you going with a limited slip as well? Complete 3.42 LSlips are pretty common under Monte SS's. 3.23 can be hard to find (if not going aftermarket).

 

[MY85pontiac]

i'm going with a richmond 3.23 gear set and an auburn unit. i figure i dont need a really beefed up posi carrier (i jsut want one so i can have traction with both tires for a change, this n/a V6 will spin tire on turns and easily in the rain) and its 300 bucks, plus an install kit and were talking 600 bucks for everything. i have a place in mind where i'll be having the gear installed.

so i'll be getting everything i need from aftermarket sources.

 

[83build-up]

just a note:monte ss had 3.73 gears not 3.42's.3.42 came in buick turbo's and hurst olds cars.and not all of either gears were limited slip.but with a non turbo six limited slip prob.isn't nessessary.3.08 or 3.23 would be good gears.anything more would need a o.d. trans for any kind of driveability within reason.

 

[b4black]

Another note than. The early MCSS's had 3.42's without OD. I think 85 was the first year for 3.73/OD.

When I said they were "pretty common", I mean that's your best bet for finding a lower ratio limited slip, not that every MCSS has one. They are more likely to have them than any other G-body. Under a 84/87 TR or HO/442 are the 8.5" and you'll pay dearly for that (and it not needed), so those really aren't an option.


$600 plus labor. You should be able to find a complete factory limited slip rear for well under $300 and it's much easy to install. (I have 3.08 LS and a 3.73 LS waiting for me get motivated and put them in )

 

[MY85pontiac]

gear set: $200
LS carrier: 300 bucks
install kit, deluxe (includes axxle bearing and seals, basically a rear end rebuild kit):about 100-125 bucks

these are not unreasonable prices.

i feel i DO need a LS unit because i can spin tire around turns and its a horror to drive in the rain. snow? fahget about it! dont even think of it.

maybe some wider tires would help (i have 215/70/14's in the back now, how much wider do i need for a basically stock V6???).

ive even spun the tire out of the hole at the local track.

still think i dont need a LS unit????



b4black.....

i considered getting a junkyard rearend but i'd be taking my chances now wouldnt i? the posi unit may be fragged, there might be a totally different gear than whats stamped into the housing or on the tag. also no guarantee how long it will hold up either, although you usually never have to worry about that. then i'd have to take all my old stuff (brakes, braklines, etc.) and put it on the junkyard unit then i'd have to switch the rears. it would probably takeme more time to do that than it would for some shop to put in the gear and LS carrier and since time is a factor to me (i cannot afford much down time with this car) i think paying someone else to do it would be better in the long run, i'd get it back on the road faster, thats for sure. not including the fact that the junkyard rear might have a bad axle,seal, bearing, etc.

yes its more money but there is a certain peace of mind knowing that i have a fresh unit in rather than one that is probably burned out or will be shortly. i also plan on hopping the engine up later so the money is being well spent in my opinion.


i do notice noone has said anything about my selection of gear or how i came to decide on this gear. does anyone thinks its too high or too low? i know i dont want to go lower than 3.23 unless i have an OD tranny (i'll be doing that {3.42 gear and a 200-4r, maybe a 3.73!} on my late grandmothers cutlass whenever i get it.). i did considered getting a 3.42 (someone convinced me "oh there's not much difference between a 3.23 and a 3.42 gear." this came from a someone with a six speed!) and then i realized thats too much gear for a car like mine. they do make a 3.36 gear though! maybe i oughta look into that???

 

[b4black]

I understand the peice of mind with the new stuff and the pro-labor. I am taking my chances with the factory units, but if they are worn out, then I'll have them rebuilt after I get them on the car. I'm just being cheap - something I need to get over . Confriming the ratio on a used rear is pretty easy (spin the axles and count the times the pinion turns).

I said either the 3.08 or 3.23 sounds good (so did 83build-up). I have the 3.08/non-OD in my 82 and it's great on the hiway. The 3.23 can' be too much diferent. If Buick would put as 3.23/non-OD in a factory car, than it can't be too bad hiway or fuel mileage (a big concern back then). I would go with the 3.23 if I had the choice, but I think the 3.42 is too much without OD.

Finding a complete 3.23, let alone a LS, has got very hard. Very few cars came with a 3.23. Maybe that alone is enough reason to go with the aftermarket.

Richmond gear's website has a great calculator for figuring out RPM's with different ratios. I used it too convince myself that going from a 3.42 to a 3.73 would not be a problem. (The 200-4R OD is a 0.67 factor.)

 

[MY85pontiac]

I would go with the 3.23 if I had the choice, but I think the 3.42 is too much without OD.

thats pretty much my thoughts on it. ive heard of other non OD tranny cars with 3.23 but those were usually early 70's cars (like my brothers 71 monte carlo), i guess i've had so many cars from the 80's that anything above 3.23 seems "agressive" and thats made me nervous about "going for it" with a 3.23 gear.

Richmond gear's website has a great calculator for figuring out RPM's with different ratios.

i have used this many times figuring out what gear i want and how different size tires will effect my RPM. i figure if i go with a 3.23 gear at 40 MPH with a 26.5 inch tall tire my RPM will be 1638. with a 2.41 gear at the same speed with the same tire hieght my RPM is: 1222. quite a leap even at 40 MPH and i'm so use to this granny gear that 1600 RPM at 40 MPH seems like a lot but i notice at cruising speeds my RPM level SEEM too low because it takes forever for it to accelerate unless i nail it so its obvious i'm not getting enough "mechanical leverage". what would you call it if you push down the gas pedal to accelerate and hear the engine rpm go up and you see this on the tach (factory unit and i yanked the clock out for this and i'm so glad i did) and you feel the slightest extra amount of power pushing the car to go faster but you feel more like you're just spinning your tires? it takes a d!ck year to accelerate unless i floor it and i'm tired of flooring it, everyone thinks i'm trying to race them (thanks to my ever so wise decision to use a hooker maximum flow muffler, it certainly uncorked the exhuast, a tad too well perhaps) and i'm wasting gas in the process. im also having to floor it just to keep up with traffic at green lights, this gear simply will not give me a break! it COULD be worse, i COULD have a 2.14 gear like some other g-body cars were given (like malibus with the 229 V6! ). of course once i get the 3.23 gear i'll be a danger to myself and everyone else on the road, i simply will not be able to resist playing with it once its in, who could say "no i will be a good little boy and drive like a normal human being after my car has been given a boost in the performance department?" its like you getting a new turbo and not "testing it out".

speaking of "testing" things out i have read you should take it easy when you get a new gear put in your car for a certain amount of miles, have the fluid changed and then you can drive normally. also no burn outs or driving above a certain speed (or rpm, i forget) so the gears dont get too hot, basically tempering them during the break in period. is this true? i want to make sure i treat them right during the break in period so they'll treat me right later on when i need em the most (like every time i go driving!).

i love my car but HATE HATE HATE this god forsaken gear!

 

[MY85pontiac]

i think i changed my mind.


i was at richmondgear.com and played with their calculator.....i think i'm gonna go with the 3.08 gear instead, its still a big leap forward but i have to think about gas milage and while there is only a 100-400 RPM difference between the 3.23 and the 3.08 gear through out the RPM range, thats enough of a difference to either give me or take away an extra gallon or two per mile and thats adds up fairly quickly on a daily driver.

now an alternative to this is to get the 3.23 gear and get a slightly taller tire later on, these tires are only 26.5" tall and seem kinda "short" short to me, narrow also but one thing at a time here. that way it will act more like a 3.08 later on when i get bigger wheels and tires. beats getting bigger tires later and having a 3.08 act like a 2.73...........hmmmmm


guess i really should discuss tire size too.

 

[RCI2990]

go with the 3.08, i had the 2.41 and got the whole rear out of a 83 parts car.made a world of difference.

 

[MY85pontiac]

i probably will go with the 3.08. i cant tell much difference in RPM below 40-45 MPH but more of a difference above 45 MPH which where the car usually sits, about 50 MPH and that will effect gas milage.

the other night i was out i downshifted into 2nd gear at 40 MPH and it was running at the same RPM as a 3.23 gear would run if it was in automatic. i'm not sure if it would feel the exact same way but when i hit the throttle i noticed a much bigger repsonse. however i wasnt thrilled at cruising around at 1600 RPM at 40 MPH, maybe i'm just too use to this 2.41 granny gear because RPM at 40 MPH is 1200. the RPM for a 3.08 gear at the same speed is 1500. a tad better and probably right where i want it.

but a 3.23 would probably give me a faster launch.
and i do notice the torque seems better about 1500 RPM and up.

I JUST CANT DECIDE!!!!! they need a gear set in between! lol

i guess at this point anyting would be an improvement over a 2.41 gear and i probably shouldnt worry too much about which gear i get. i think ultimately i'd be happier with the 3.23. i will be getting 15 x 8 pontiac rallyes and a slightly taller tire than the one i have now so that will "slow down" the gear a tad. i suppose i could just live with the crappy gas milage, its gonna be crappy anyway.