Chevy Impala SS Forum banner

1 - 20 of 64 Posts

·
Registered
Joined
·
34 Posts
Discussion Starter #1
My 1996 has 40,000 miles and I am considering going to a 3.42 rear end. My question is, how would this affect the way the car drives/performs. Would I find it a noticeable change from the stock rear end?
Also, does anyone have any experience with a good drive line shop in the Tampa Bay area that could do this type of swap for me.
I already have a Hypertech pro, so can easily reprogram for a different rear end ratio. thank you.
 

·
Registered
Joined
·
1,903 Posts
My 1996 has 40,000 miles and I am considering going to a 3.42 rear end. My question is, how would this affect the way the car drives/performs? Would I find it a noticeable change from the stock rear end?
Your SS already has 3.08, so, your butt-o-meter might be underwhelmed by 3.42, if our experience is any indication.
The ISSF's history shows that, PRIOR to the fuel price crisis that preceded cashforclunkaz, most of the 9C1s & SSs that upgraded from 3.08 to 3.42 regretted not going to 3.73 - because 3.08 is simply too close to 3.42.
(Maths: 3.42 is 11% more axle than 3.08. 3.73 is 21% more gear than 3.08.)
Many of those later upgraded from 3.42 to 3.73, noting slight highway MpG penalties, and the possibility of driveshaft vibes; note that 3.42 always avoids both.
I still wonder, how many B-sedans and B-wagons with 3.73 later got cashed & junked for a weaker car with better MpG?

I had a 2.56 wagon. Upgrading to 3.42 was THE BEST thing that EVER happened to that wagon without question. (33% improvement.)
My next Caprice 9C1-LT1 sedan got upgraded to 3.73 before I bought it.
Definitely more fun, it got slightly better city MpG, but also worse highway MpG than my heavier wagon.

2.56, 2.73, 2.93, 3.08, 3.23, and the L99 V8 are the result of anachronistic Corporate Average Fuel Economy tests.
All B- & D- cars should have come with 3.42, 3.57, or 3.73 from the showroom floor.
 

·
Registered
Joined
·
8,390 Posts
Good collection of intel. Reminds me of popularity of the V4P Fleetwood tow option, which (in addition to 'factory secret sauce' special tranny shifting line pressures and some different parts) includes 3.42 v. the Brougham's stock 2.92 for quite a (comparative) jump. I believe the base Fleetwood got 2.56???? With a tune and a few add-ons my driver can get out of its own way quite well for a 5,000# tub, but those who've changed to 3.42s report really waking it up.

For the OP I'll offer that with my '96 garage queen's 80k and original Aurburn long dead that when I upgrade it's gonna be 3.73 and Eaton LSD all the way. Yours at half that mileage is obviously not a turnpike daily driver, so the business case for 3.73 seems rather apparent. JIMHO
 
  • Like
Reactions: Marky Dissod

·
Registered
Joined
·
1,903 Posts
It's a fact that V4P did not sell ANYWHERE NEAR as many as WX3 & WX8.
WX8 & V4P are probably far closer to each other in terms of sales.

An NM8 V4P is a black swan …
 

·
Registered
Joined
·
8,605 Posts
My $.02

Original owner so started 3:08....then 3:42. IMHO best "all around" gear for a street/Fwy car. I also did at the time of gears was a 2200 stall, Transgo shift kit, 1:6 RR and a mail order tune (Ed Wright). For me it was the best combo I had when my SS was a automatic. I did go 3:73 as I had been taking the car to the track since 97. I drive a lot of Fwy and hated the RPM with 3:73

Swapped in a T56/4:10's in 05 :)
 

·
Registered
Joined
·
34 Posts
Discussion Starter #6
My $.02

Original owner so started 3:08....then 3:42. IMHO best "all around" gear for a street/Fwy car. I also did at the time of gears was a 2200 stall, Transgo shift kit, 1:6 RR and a mail order tune (Ed Wright). For me it was the best combo I had when my SS was a automatic. I did go 3:73 as I had been taking the car to the track since 97. I drive a lot of Fwy and hated the RPM with 3:73

Swapped in a T56/4:10's in 05 :)
Great ! Thanks, all good information. I also have a Transgo shift kit dialed way back to stifle some of the moaning from the passenger seat, and Hypertech Pro, 160F thermostat and K&N PIJK.
With 40,000 from new and being a Fla car that I don't drive in the rain, I don't do much highway, but I suspected that the 3.73 might result in maybe too high rpm. Good to hear your experiences.
 

·
Registered
Joined
·
34 Posts
Discussion Starter #7
Your SS already has 3.08, so, your butt-o-meter might be underwhelmed by 3.42, if our experience is any indication.
The ISSF's history shows that, PRIOR to the fuel price crisis that preceded cashforclunkaz, most of the 9C1s & SSs that upgraded from 3.08 to 3.42 regretted not going to 3.73 - because 3.08 is simply too close to 3.42.
(Maths: 3.42 is 11% more axle than 3.08. 3.73 is 21% more gear than 3.08.)
Many of those later upgraded from 3.42 to 3.73, noting slight highway MpG penalties, and the possibility of driveshaft vibes; note that 3.42 always avoids both.
I still wonder, how many B-sedans and B-wagons with 3.73 later got cashed & junked for a weaker car with better MpG?

I had a 2.56 wagon. Upgrading to 3.42 was THE BEST thing that EVER happened to that wagon without question. (33% improvement.)
My next Caprice 9C1-LT1 sedan got upgraded to 3.73 before I bought it.
Definitely more fun, it got slightly better city MpG, but also worse highway MpG than my heavier wagon.

2.56, 2.73, 2.93, 3.08, 3.23, and the L99 V8 are the result of anachronistic Corporate Average Fuel Economy tests.
All B- & D- cars should have come with 3.42, 3.57, or 3.73 from the showroom floor.
This is some great information too. Thank you. I wondered if the 3.42 might not result in a significant butt-oneter charge. So maybe I should go with 3.42 and perhaps a NOS shot. Nothing too extreme, just wake her up a bit. Of course I start going down this route after driving the F-type V8S, which is just brutal. Just a bit more in the Impala would make me happy............But when is more power enough, that is the question?.
 

·
Registered
Joined
·
34 Posts
Discussion Starter #8
Good collection of intel. Reminds me of popularity of the V4P Fleetwood tow option, which (in addition to 'factory secret sauce' special tranny shifting line pressures and some different parts) includes 3.42 v. the Brougham's stock 2.92 for quite a (comparative) jump. I believe the base Fleetwood got 2.56???? With a tune and a few add-ons my driver can get out of its own way quite well for a 5,000# tub, but those who've changed to 3.42s report really waking it up.

For the OP I'll offer that with my '96 garage queen's 80k and original Aurburn long dead that when I upgrade it's gonna be 3.73 and Eaton LSD all the way. Yours at half that mileage is obviously not a turnpike daily driver, so the business case for 3.73 seems rather apparent. JIMHO
Again, great information. Thank you.
 

·
Registered
Joined
·
34 Posts
Discussion Starter #9
This is some great information too. Thank you. I wondered if the 3.42 might not result in a significant butt-oneter charge. So maybe I should go with 3.42 and perhaps a NOS shot. Nothing too extreme, just wake her up a bit. Of course I start going down this route after driving the F-type V8S, which is just brutal. Just a bit more in the Impala would make me happy............But when is more power enough, that is the question?.
Now I need to troll through the Forum to find the optimum dry Nitrous system for a basically stock LT1. And if available in Florida LOL
 

·
Registered
Joined
·
8,605 Posts
NOS on a street car...IMHO not the best thing. The pistons are not forged so stock hyper pistons don't put up with NOS for long. The design of the LT1 intake manifold make the NOS apply more to #7&8 so they take the beating. You will also need a PCM tune, likely a colder plug to be able to run NOS

If you really want to make more power do heads & cam....but the rabbit hole can get pretty deep when you start those kind of mods

About gears, You can use a online calculator to show what RPM at what speed with what gear and tire size you have. My $.02 is 3:73's made 75 mph hwy driving to high RPM, just my choice with the 4L60E. Some may not care
 

·
Registered
Joined
·
629 Posts
OP
I was in a similar situation choosing between 3.73 and 3.42
I went with the 3.42 and have loved it. I use my Impala mainly for Road Racing and Autocross and then sometimes drag racing.
Michael
 

·
Premium Member
Joined
·
89 Posts
Back when I had a stock car, I went 3.73 and loved it. One of the biggest "bang for the buck" mods you can do.

I've also run nitrous on quite a few cars. Keep in mind that to run a reasonably "safe" dry nitrous kit, you will want to have a way to ensure the nitrous does not come in without sufficient gasoline pressure, that it does not come in without achieving a minimum rpm, and you will probably also want a purge kit to keep from stumbling, and eventually you will want a remote bottle opener.
When you add up a complete nitrous kit, you are near the cost of the rear end gear change.
Besides being slave to keeping a full bottle, I like the way rear end gears are felt from a dead stop, as well as every time you hit the gas. Nitrous is fun, and can be done safely, but I feel the gear change is more "usable".

It is a slippery slope, but you should start with 3.73's, then do the nitrous. Then when that is still not enough, you can move to the heads and cam (right before you decide you need to build a 383) :D
The only thing that can stop you is money. lol
 

·
Premium Member
Joined
·
89 Posts
However, if you keep buying the same model car, the nitrous kit transfers a little easier than the rear end

black nitrous.jpg
nitrous in spare tire well - blue.jpg
 

·
Registered
Joined
·
1,903 Posts
The 3.73 vs 3.42 Questionnaire
1. This is my toy, not my daily driver?
Y=3.73
N=3.42

2. I'm gonna race, or 'play hard' [for money]?
Y=3.73
N=3.42
(also see ?#6, unless you are kidding yourself)

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

4. I care more about city MpG, less about highway MpG?
Y=3.73
N=3.42

5. Many or mostly steep &/or very long hills where I usually drive?
Y=3.73
N=3.42

6. I've an extra $600 lying around, just in case I NEED to buy and install a new driveshaft?
Y=3.73
N=3.42

7. My valvetrain has [AT LEAST] 1.6 roller rockers AND upgraded valvesprings to support a WOT UpShift of at least 6,000RpM or higher (I've also headers)?
Y=3.73
N=3.42
(see ?#1 & ?#2)

If 'N'= 7, you tend to get >21MpG, prefer 3.08 / 2.93 / 2.5625, will probably never ask this question, and yet still uninterested in open loop tuning for more MpGs for some reason …
If 'N'= 4 or 5 or 6 then get 3.42, keep the 9C1/WX3 driveshaft, save on highway MpGs, 3.73 might still lose in the 1/4mile without more upgrades anyway …
If 'Y'= 4 or 5 or 6 then get 3.73 - and maybe a driveshaft upgrade? Or, Maybe not? Who knows? Test to find out - then ask those with 4.11 about your next upgrades …
If 'Y'= 7 then you NEED 4.11 or more, a definite driveshaft upgrade, a torque converter upgrade, headers, heads & cam … or a Gen3 / Gen4 V8 swap … did you marry well?

You also want to upgrade the limited slip differential.
If you don't have a limited slip differential, then you definitely need one.
If you upgrade your torque converter, upgrade your external transmission cooler.
 

·
Registered
Joined
·
34 Posts
Discussion Starter #16
NOS on a street car...IMHO not the best thing. The pistons are not forged so stock hyper pistons don't put up with NOS for long. The design of the LT1 intake manifold make the NOS apply more to #7&8 so they take the beating. You will also need a PCM tune, likely a colder plug to be able to run NOS

If you really want to make more power do heads & cam....but the rabbit hole can get pretty deep when you start those kind of mods

About gears, You can use a online calculator to show what RPM at what speed with what gear and tire size you have. My $.02 is 3:73's made 75 mph hwy driving to high RPM, just my choice with the 4L60E. Some may not care
Good information. I'm just wondering with my current less than 500 miles per year that I drive this car, and no plans to race or drag it, would limited use of a low hp nitrous kit really have such dire effects on the pistons? Abuse, I get that, but I wonder if there are examples out there of other low mileage LT1s with nitrous that have survived.
 

·
Registered
Joined
·
11,311 Posts
I currently have a 3.42 in my wagon with a 454. I built the rear myself, and now have the tools to build another one. I am in Largo, and would consider building one for you at your house for a fee. If you get all the correct parts it will not take too long. It is not any different building a 3.42, or a 3.73, other than the gear set. One thing I will suggest is that you buy the very best parts you can afford. I would upgrade the posi, and get new axles/bearings while you have it apart. Moser makes nice axles, and they are about the same price as the Chinese ones. I bought an axle from the junk yard, so I did not have down time while building mine.
 

·
Registered
Joined
·
8,605 Posts
OP

a 50 shot is likely the lowest shot of NOS you can get. Its a cheap go fast part...but hyper pistons and NOS= short life. + the tuning, fueling and injectors then the cost starts to add up.

If you want more power do a Lloyd Elliott heads & cam package with a good tune and you will have 100 more RWHP and the motor will live a long life

cheapest acceleration improvement would be gears
 

·
Registered
Joined
·
34 Posts
Discussion Starter #20
OP

a 50 shot is likely the lowest shot of NOS you can get. Its a cheap go fast part...but hyper pistons and NOS= short life. + the tuning, fueling and injectors then the cost starts to add up.

If you want more power do a Lloyd Elliott heads & cam package with a good tune and you will have 100 more RWHP and the motor will live a long life

cheapest acceleration improvement would be gears
Yes, heads, cams and axle ratio information is really helpful. Thank you.
 
1 - 20 of 64 Posts
Top