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Discussion Starter #1
So as some of you may have seen in other threads lately, I have been doing a LOT of pondering on what to do with my tire/budget situation... I had 235/60/15s on the front, and 255/60/15s on the rear in the ever-popular Firestone Indy 500s. But as some of you know, those have been discontinued... So I was trying to go to the 2010-13 Camaro base model 18" black wheels with custom adaptors made, but it ended up exceeding my budget by a bit... I did not want to go back to original type 225/75/15 whitewalls, and they are not making many tires in the 255/60s anymore and none at all that I feel are resonably priced... So this weekend I ended up talking myself into going 235/60/15 all the way around(Primewell PS 860s - $80.00/ea.). This way I will be able to rotate them and get a bit more mileage out of this set. They will also be a little lighter, and being 26" tall they will raise my effective gear ratio from 2.56:1 with stock size rubber to 2.78:1(according to the tire size/gear ratio calculators) which will help a tiny bit in acceleration(and I'll take every little bit I can get)... I am not entirely happy with the appearance, especially going down from the 255s, but I will get used to it I suppose. My car is pretty low, so I can get away with them ok without it looking stupid - like the car has casters instead of wheels. But it's close. LOL... I'll tell you what though, overall I am pleased with the choice. I recalibrated my speedo with my Hypertech, and have driven the car about 100 miles or so. The car is DEFINITELY a little quicker... doesn't fall flat on it's face anymore when it goes into 2nd, which is nice... and I even heard a little baby "chirp" a few times yesterday when I stood on it during the 1-2 shift. Hoping for a 14.6 next time out at the track... not bad for almost bone stock with 2.56s and full furniture... :)
 

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Discussion Starter #2
Driveshaft ???

... was just thinking about something... I am going to be putting a set of gears in my car and a posi unit before too long, and was just messing around with the tire height/gear ratio calculator again and I see that with my current size tire, my "effective gear ratio" with the 3.42's I planned on going with is going to be 3.71:1... Anyone know if this is going to throw me into the "if you go 3.73's or 4.10's, you will need an aluminum driveshaft, or you may experience vibration at highway speeds" category?... My mind logically tells me that it indeed will, but just want to run it by some of you to see if you've had the experience... If so, I may go 3.23's, whic will put my "effective ratio" at 3.50:1... May be better off that way. Damn driveshafts are pricey. I'd love to do one eventually, as it sounds like a good upgrade to ditch some more unsprung/rotating weight, but we're not all made of money... one thing at at a time.... Thanks...
 

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Discussion Starter #3


3.42 may not be the best mod ever, but 2.56 is in the running for the worst oem option ever.
Enough about what GM did wrong …​


DEFINITELY AGREED BROTHER

I love the questionnaire... That's some good stuff, and a great way to look at it. That being said, I have done probably even more possibilities than you listed for the tire height/rear gear ratios. LOL... I JUST got my 26" tires, so I am definitely not changing them any time real soon. I feel after reading the info you provided, and going through the questionnaire a bunch of times I am DEFINITELY going 3.42s, giving me the "effective ratio" of 3.71:1..... I'm just going to hold off on doing it until I gather the funds for that nice new driveshaft. :) Thanks man!
 

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… was just thinking about something …
going to be putting a set of gears in my car and a posi unit before too long, and was just messing around with the tire height/gear ratio calculator again and I see that with my current size tire, my "effective gear ratio" with the 3.42 I planned on going with is going to be 3.71:1 …
Anyone know if this is going to throw me into the "if you go 3.73's or 4.10's, you will need an aluminum driveshaft, or you may experience vibration at highway speeds" category? …
My mind logically tells me that it indeed will, but just want to run it by some of you to see if you've had the experience …
If so, I may go 3.23's, which will put my "effective ratio" at 3.50:1 …
May be better off that way. Damn driveshafts are pricey. I'd love to do one eventually, as it sounds like a good upgrade to ditch some more unsprung/rotating weight, but we're not all made of money …
one thing at at a time …
Thanks …
Recently liberated my wagon from 2.56, with 3.42.

3.42 may not be the best mod ever, but 2.56 is in the running for the worst oem option ever.
Enough about what GM did wrong …​
The 3.73 or 3.42 questionnaire:

1. I'm gonna race, or 'play hard' [for money]?
Y = 3.73 [or more] N = 3.42

2. I'm gonna tow/haul, or 'work hard' [for money]?
Y = 3.73 N = 3.42

3. Lotsa steep hills where I tend to drive?
Y = 3.73 N = 3.42

4. I care more about city MpG, less about highway MpG?
Y = 3.73 N = 3.42 (If you do no highway driving whatsoever, consider 4.10)

5. I have an extra $400 lying around, just in case I NEED to buy a new driveshaft?
Y = 3.73 N = 3.42

6. My valvetrain has [AT LEAST] 1.6 roller rockers and upgraded valvesprings to support a WOT UpShift of at least 6,000 RpM?
Y = 3.73 N = 3.42

7. This is my toy, not my daily driver?
Y = 3.73 [or more] N = 3.42

If 'Y' is greater than 'N', get 3.73
If N>Y, get 3.42​
Unless you can get 3.23 for $100 or less, it's either 3.42, or 3.73.

Nobody KNOWS if the driveshaft is gonna impersonate a guitar string, until it is actually tested by a highspeed test - which basically simulates installing 3.73 and spinning the driveshaft yourself at 80+MpH in 4th, except OUT of the car.

IFF YOU KNOW you're gonna buy a driveshaft later, get 3.73 along with the tallest tires you can stuff in the wheelwells. Tires are much easier to change than rear gears.

3.73 & 29.50" tall tires = 3.42 & 27.05" tall tires - identical engine RpMs in all gears, at all road speeds
3.73 & 27.92" tall tires = 3.42 & 25.60" tall tires

3.42 & 29.50" tall tires = 3.23 & 27.86" tall tires
3.42 & 27.11" tall tires = 3.23 & 25.60" tall tires

3.23 & 29.50" tall tires = 3.08 & 28.13" tall tires
3.23 & 26.85" tall tires = 3.08 & 25.60" tall tires

3.08 & 29.50" tall tires = 2.93 & 28.06" tall tires
3.08 & 26.91" tall tires = 2.93 & 25.60" tall tires

and in case you were wondering

3.42 & 29.50" tall tires = 3.08 & 26.57" tall tires
3.42 & 28.43" tall tires = 3.08 & 25.60" tall tires

But for the unpredictable possibility of needing to buy an aluminium or MMC driveshaft, nearly all the arguments for 3.42 would vanish; everyone would just get 3.73 [if not 4.10] and adjust to taste with the tire of their choice.
DEFINITELY AGREED BROTHER
… love the questionnaire … That's some good stuff, and a great way to look at it.
Trying to help someone figure out what they should do, is not the same as simply telling you what I'd do, and saying you should just do that too.
The statistical ISSF consensus, at least until recently, was 3.73-and-that's-the-end-of-it, with 4.10 for those with heavier wheels, or many very serious mods.
Problem is, with 3.73:
a. you can't predict if the driveshaft will sing or not
b. the more you like to 'speed' on the highway, the more 3.73 will cost you MpG on the highway, depending on tire height
c. the more you like to 'speed' on the highway, the less likely you are to be able to access the 4-2 double downshift, depending on tire height
With 3.42, the driveshaft is almost guaranteed not to sing, it won't cost any highway MpG unless cruising at 85MpH or more, and the 4-2 double downshift is way more accessible/likely.
That being said, I have done probably even more possibilities than you listed for the tire height/rear gear ratios. LOL … I JUST got my 26" tires, so I am definitely not changing them any time real soon.
Never suggested you waste the tires you already have. When it comes time to replace them, though, if your highway MpGs have suffered, or your driveshaft impersonates a guitar string, taller tires will definitely help.
… feel after reading the info you provided, and going through the questionnaire a bunch of times I am DEFINITELY going 3.42, giving me the "effective ratio" of 3.71
Driveshaft resonance with 3.42 would be a nearly-unheard-of statistical anomaly.
If your driveshaft somehow manages to impersonate a guitar string, either slow down on the highway, or install taller tires - they'll push its resonance frequency further up the speedometer.
… I'm just going to hold off on doing it until I gather the funds for that nice new driveshaft.
OK, technically, this is not the kind of advice I prefer to give, but …
Seriously, do NOT hold off on 3.42; you're wasting time, possibly money, and definitely fun.
Knowing what I know now, when I 1st bought this wagon, I'd've IMMEDIATELY acquired and installed 3.42, even if forced to go without a limited-slip differential (not required, but so highly recommended, a posi should be required).
3.42 has improved both my MpGs and my enjoyment, and would likely have prevented/delayed at least one or two transmission rebuilds [effectively subsidising 3.42].

These cars should NOT have come with 2.56, 2.73, 2.93, or 3.08 [or the 4.3L L99 V8; damn CAFE!].
(3.23 with taller contact patches is as effective as 3.08 with OEM tires, and since when is more rubber on the ground a bad thing? Most vehicles as big and heavy as ours have taller tires with larger contact patches.)​
Only gears that belong on these cars are 3.23, 3.42, 3.73, and 4.10, and 4.56 for the manual six-speed crowd.

Again, with 3.42, driveshaft vibes should be no concern - I'm vibe-free, baby, and I doubt you'll find anyone with 3.42 who has vibe issues - but if you want to be [overly] cautious, start looking for
93-05 Ford Clown Victrola P71 Police Intercept-her Metal Matrix Composite Driveshafts (seriously!).
Otherwise, just install 3.42 already! You'll be glad you did!
 

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Discussion Starter #5
Gotcha... all sounds reasonable to me... I intend to one day put a T-56 in mine and go to at least 4.10s, but that's WAY WAY off from now... So I'll be grabbing me a set of 3.42s for now and havin' at it :) I can't talk myself into doing the gears without doing the posi unit at the same time, so that's pretty much all that's holding me back at this point... Friggin' thing absolutely FRIES the tire now with the 2.56s if you mash it... I can't imagine that it would EVER move off with the 3.42 / 26" tall tire combo without posi. I keep going out to the local junkyards looking for a '89+ van to grab a posi out of but haven't had luck yet... Been a few 9C1s out there and even an Impala, but they've all had 300,000+ miles on them and I'm sure are they're shot. The van rears from what I've heard have a different type of posi in them, and are rebuildable unlike the weak gov-locks... Correct me if I'm wrong on that... just trying to get out of a damn $500 aftermarket posi if i can help it.... Thanks again for the great help man :)
 

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Discussion Starter #7
damn good post..i am gonna put a set vof 3.42 since a have a set from my old jimmy just lying around..

Glad it helped you out bro... sounds like a great upgrade to our lousy 2.56s... finally be going through the traps in 3rd! Woo hoo... should feel a s*it-load quicker... I'm guessing it'll be worth about 5-7 tenths in the quarter or so :D ... traction permitting.
 

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Glad it helped you out bro … sounds like a great upgrade to our lousy 2.56 … finally be going through the traps in 3rd! Woo hoo … should feel a $h!tload quicker … I'm guessing it'll be worth about 5-7 tenths in the quarter or so :D … traction permitting.
How much power does 3.73 liberate compared to 2.56?
Short answer: compared to 2.56, 3.42 liberates / puts down to the ground about another 60 horse.

Here's how I figure:

Caprice 9C1-L99 has 200 horse, 3.23, tops out around 130MpH [eventually].
Caprice 9C1-L05 has 200 horse, 3.42, tops out around 130MpH [sooner].

Caprice Wagon LT1 260 horse, 2.56, tops out around 131MpH [gave up, acceleration barely detectable].
Same Caprice Wagon LT1 with 3.42, tops out around 140MpH [gave up, running out of room].
Caprice 9C1-LT1 has 260 horse, 3.08, tops out around 140MpH [gave up, running out of room].
For the record, if it wasn't for:
the distinct and unpredictable possibility of driveshaft resonance
the hiway MpG penalty (prefer to cruise between 65-85MpH)
let there be no question that I'd've immediately chosen 3.73 over 3.42.

Oh, and one more thing, by the stopwatch:
2.56 0-60MpH = 8.4 - 8.7, depending on traction (griping again)
3.42 0-60MpH = 6.8 - 7.3, depending on traction
The above maths are VERY amateurish, but even if clumsy, still makes the case against 2.56, and for 3.42 or more gear.
 

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The above maths are VERY amateurish, but even if clumsy, still makes the case against 2.56, and for 3.42 or more gear.
That's rather encouraging to hear... That's a huge difference man. I did about 6 stopwatch tests of 0-60 in mine, and was an avg of 6.7 each time over the 6 tries... and that was when I had the 27" tires on the car... If I can launch it on the 26"ers without blowin' the tire off(haven't tried yet), should be a hair quicker... Can't WAIT to see what the 3.42s do for me with the 26" tire combo... Is it absurd to think I could possibly break into the 13s(traction permitting) just doing the gear swap(and posi, not that the makes it quicker, just makes it able to move instead of sitting in one spot wasting hard-earned rubber. LOL)? I mean, I go 14.7 now... That would REALLY make me happy... I don't really have sh*t done to my car(in my sig. is IT) and it runs GREAT already... for what it is.
 
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