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.

 

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?.

 

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.

 

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 …

 

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.

 

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.

 

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

 

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)
The only thing that can stop you is money. lol

 

However, if you keep buying the same model car, the nitrous kit transfers a little easier than the rear end

 

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.

 

Thanks, a good checklist to help with decisions.

 

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.

 

Thank you, that's good to know. I'm still kicking around options but will keep you in mind, if and when I make a decision.

 

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.

 

NOS on a stock car that drives on the streets. Someone has been watching too many fast and furious movies.

 

Thanks. That's helpful and exactly why I was looking for ideas on this Forum from knowledgeable and experienced people on the pros and cons on performance improvements for the LT1. ............Because I watch too many fast and furious? movies. Being significantly older than 16, I have no idea what these movies are about.

 

Like BALLSS said:
Lloyd Elliott is an LT1 heads and cam guru:

LT1 LE1 «

If you can do the wrenching yourself, you can keep the costs down. If not, the rear axle gear change remains the "bang for the buck" winner.

 

Yes, sounds like the best option. I like the Lloyd Elliott approach too. Once it cools down here in Florida, I will be ready to start wrenching on that car. Just a bit too sweaty right now.🙂

 

I installed 3.42 and now have a set of 3.73's sitting on the shelf for install. Wish I'd gone with 3.73 first.

 

Installed 3.42 and now have a set of 3.73 sitting on the shelf for install. Wish I'd gone with 3.73 first.

May I ask, what result do you get from answering the following 3.73 vs 3.42 questionnaire?

3.42 rear end impressions?

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...

www.impalassforum.com

 

Interesting. First hand experience is always the best. Thank you.

 

I bought Richmond 3.73's and Moser axles from summit this weekend, was that a good choice? I haven't installed them yet so i'll take them back if not.

 

Richmond gears are very good. They are now made in Italy. Moser axles are also good

I assume you bought ABS compatible gear set and also a reluctor gear for the 3:73's?

If you still have the stock Auburn limited slip diff, assuming you have a LS car, replacing it with a Eaton LS is a no cost labor if you do it during a gear swap. The stock Auburn units are marginal at best

Also get a "Master Install Kit" which includes all the bearings to do on a gear swap. Generally about $100

 

Well, for me, it has to be 3.73 based on all the great Forum information, the decision tree questionaire, and my personal wants.

 

Well, for me, it has to be 3.73, based on all the great Forum information, the decision tree questionnaire, and my personal wants.

If 3.73 is not enough, but you manage to choose your torque converter carefully, you'll preserve the ability to get decent city / metro / urban MpGs when you do somehow keep your foot out of it.
Choose poorly, and no matter how you drive, you'll always waste MpGs even when you're driving to get decent MpGs.

I enjoyed 3.73 very much while I had them, especially when I was NOT on the highway, especially in Manhattan.
Once I got on the highway, though, cruising over 75MpH for any length of time was extremely difficult and uncomfortable, even using 235/75R15.

 

I don’t know what all this RPM talk is about?! WE HAVE Overdrive!!! I have a built 96 DGGM 383 with a truetrac posi rearend 3.90 gears on 285/30/20s. I drive around town in 3rd gear. Overdrive on highway. No rpm issues

 

I don’t know what all this RPM talk is about?! WE HAVE Overdrive!!! I have a built 96 DGGM 383 with a truetrac posi rearend 3.90 on 285/30R20. I drive around town in 3rd gear. Overdrive on highway. No RpM issues.

With 383 cubes, 3.90 & 26.73" tall tires, at what speeds are you driving 'around town'?
'cause I'm sure that if I had a 6.28L engine with 3.90 gears & 26.73" tall tires, I could be in 4th by 18MpH.
Some overdrives are better than others - same goes for driveshafts.

 

I don’t know what all this RPM talk is about?! WE HAVE Overdrive!!! I have a built 96 DGGM 383 with a truetrac posi rearend 3.90 gears on 285/30/20s. I drive around town in 3rd gear. Overdrive on highway. No rpm issues

 

I went back and forth from 3.42 to 3.73 gears a number of times and really prefered the 3.73. They made the car feel more spirited and fun to drive. I tested for fuel mileage and they both stayed within 1 mpg city and highway of each other driving normally. At the track times were slightly better with the 3.73, but not as much as I thought, but this was due to wheelspin with the 3.73 and stock tires. You will never regret the driving fun with 3.73 gears

 

All this handwringing over a couple hundred rpm difference on the highway. Why spend the same money to go halfway? It's the deeper gears that allow the 9.5" torque converters with better driveability, instead of worse. Converter should be locking up above 45-50mph. anyway making stall speed on the highway equally irrelevant.

 

I absolutely agree that checklist is pretty sweet! My DGGM is restomod/prosthetic type set up, not a daily driver. I have (2) neighbors with mustangs. Yesterday, the ******* with the newer mustang drove by my garage overrevving in first gear giving me the stare down... My sole wish in life is to gap their FUCKING ass with this 4500# monster every chance I get! So yeah I can give two schitts about MPG and emissions

I’m pretty sure my reluctor came off an 1990 454ss truck. I’ll see if I can dig the p/n up,, it was discontinued last time I looked. I’m building an 11.35sec car (I ran 14.85 with stock set up + hooker shorty headers rolling in 20s). Since, I’ve upgraded to LT4 block with Forged internals, AFR 210 heads (1.6RR) and CIA long tubes. I’m Running about 11.5:1 compression with rev-limit of about 6500prpm.

transmission has been completely upgraded with 5 pinion planetary gear sets. Firm/aggressive shift. I also manually tuned the shift points in cold/hot/wot modes going up and down.

I also swapped in a 2004 crown Vic (police) driveshaft.

currently getting dynotuned for 200hp shot of nitrous.

 

I’m pretty sure my reluctor came off an 1990 454ss truck. I’ll see if I can dig the p/n up,, it was discontinued last time I looked. I’m building an 11.35sec car (I ran 14.85 with stock set up + hooker shorty headers rolling in 20s). Since, I’ve upgraded to LT4 block with Forged internals, AFR 210 heads (1.6RR) and CIA long tubes. I’m Running about 11.5:1 compression with rev-limit of about 6500prpm.

Sounds like you have a nice build there! After I discovered 383s, I'd never rebuild a 350 into a 350 again. LOL. The 383s are cheap(ish) if already doing a build and much more fun! Of course big blocks and LS swaps are fun too. But if sticking to a SBC, 383 is the easiest way to go with tons of options.

And this reinforces my previous point. Gear selection is much more than just a discussion about RPMS. 3.42 versus 3.73 is about the best choice we have with a stock or mildly upgraded engine/drivetrain. Anything more than 3.73, you need a bigger build! (IMHO)

 

Oh Yessir! I wanted 550-600hp on motor NA. It took a bunch of advice from some of the vets on this forum. I used the golen and lingehfelter engine build sheet(s). I’m about 575hp at the flywheel now. Still have good 60ft #s. Tuning the trans was the game changer! They are a lot of 94-96 b-body owners that just punted because DIY on this LT1 schitt ain’t easy.

 

I agree. I don't want to swap an LS into it. I like the LT1. I'm torn about what to do with it. Because a lot of Dodge cars love pulling up and acting crazy from light to light.