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Discussion Starter · #1 ·
Sorry for asking these dumb questions, but I gotta' go with my strengths - and asking really stupid questions is about the only strength I have...

I'm up-gearing Bubba*, a '96 RM wagon with 2.56 gears. It's ridiculous - at 70 mph on the highway the poor engine (bone-stock LT1 and staying that way) isn't even turning 1,600 rpm; and torque peak for most piston engines sits at 1,700 rpm. So to put the torque peak where I want it on our roads, which are mostly pothole-on-pothole and speed limit 60 mph, I'm thinking 3.23 gears (and no, I really don't want higher - the LT1 is a torque monster and gas here is currently north of $8 (Cdn) a gallon; 'n besides, I LOVE how quiet Bubba is!) But Bubba being a '96, it needs a reluctor for the ABS (without which it won't pass Safety), and the 3.23 gears appear to have been an earlier offering that wasn't available during ABS and therefore, may not even have had a reluctor made for them. I'd settle for 3.08's, and even this small an increase would make a world of difference, but my first car had 3.23's and I have a soft spot in my head for that number. Does anybody care to comment:

1) where to order 3.23's that are machined for a reluctor

2) who might have or make a reluctor for 3.23's

3) it's getting a posi - not a locker - what's recommended as the best posi that'll carry 3.23's and has the right splines for stock axles, and

4) best place to get a PCM flash for higher gears and air pump delete?

Thanks much all!

*BUBBA - Big Ugly Buick Bad Attitude
 

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You're a prime candidate for 3.42's.... (3.73's only cost 1-2mpg. on highway) One can always bump up tire height to "trim" effective ratio.... Eaton Tru-Trac posi. is both highly recommended ,and a popular choice. pcmperformance.com is my favorite for PCM re-flash.
 

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We are back to " where " in Canada ?

Edit Nova Scotia , other end of Country.
I was going to try and convince you that you really needed my 3.73 posi wagon diff that is taking uo space under my bench.
While I dont recommend 3.08 , I think I have 3.08 and reluctor and might be able to supply a PCM with the gear ratio set

Try Vancouver , Premium is over 11bucks cdn for an imperial gallon !!!!!

$7.19 us for us gallon
 

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I have 3.42s in my wagon with an Eaton True Trac. I really like them, and I have a 454 stuffed in the front. I get the same gas mileage as my 3.23s did. I no longer have ABS, so I do not know where to get an ABS reluctor friendly gear set. The 3.23s were a standard with the 91-93 cars, and they had ABS. You can check with any of the big parts houses for the reluctor friendly gear sets. The 3.23 reluctors should be fairly easy to find.

An Eaton posi (not the True Track) is a reasonable option, because they can be rebuilt unlike the OEM units. They are somewhat cheaper than the True Trac units. The True Trac units require a special bearing package to install the carrier. Either will fit in your axle housing. You can use a .036-.042 inch pinion shim and be sure the mesh will be at the proper depth. Each axle needs a different set of shims for the carrier, and you need a dial indicator to check the lash.
 

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3.42 for axle gear. 235/75R15 for tires. Don't be hardheaded about a soft spot!
235/75R15 for superior pothole / schidty road defense vs225/70R15, 235/70R15, or 225/75R15.
Slightly taller tires make 3.42 perfectly suited to your needs.
Been recommending 235/75R15 - 28.87" tall - for many years now.
225/75R15, 235/70R15, and 225/70R15, each have fewer lower quality choices, vs 235/75R15.

Does Bob Shirley still sell custom ABS reluctors?

Can't disagree with Eaton TruTrac posi.
Can't disagree with pcmperformance.com - one of the few tuners of OBD2 LT1s for many years with a damn solid rep.
 

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I am running 255/50/17s on the rear, and 235/55/17s on the front. No worries for potholes.
 

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1) where to order 3.23's that are machined for a reluctor

2) who might have or make a reluctor for 3.23's

3) it's getting a posi - not a locker - what's recommended as the best posi that'll carry 3.23's and has the right splines for stock axles, and
3.23 gears and reluctors ----MIGHT---- be available at a GM dealership. All I will say to that is; "Good Luck".

Otherwise, you're talking about pulling a set out of an old 9C1. 😣

As mentioned above, you might SERIOUSLY consider a set of 3.42's. NOTE the link at the bottom for gears, reluctor and posi.

Best of luck!

KW

High Performance Exhaust Systems - Chevy Impala SS Drive Train (clearimageautomotive.com)
 
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I'll jump on the 3.42 (band)wagon. Pun intended.

I've had that ratio on my '95 9C1 sedan for 20 years, back when the reluctors were stocked by dealerships and cost less than $20/ea.

But it's not all rainbows and unicorns...

I did have to replace my driveshaft. Stock one vibrated above 65 MPH. I got in on a MMC aluminum group purchase way back in the day. If you get vibrations after the swap, then a good balance job may fix the stock one just fine. But I also recall learning that the stock ones can have weird higher RPM resonance problems at certain speeds, unsure if a stock one is ever safe to run at higher gear ratios and higher speeds.

You will need a PCM tune to deal with the speedo calibration.

That said, 3.42 makes a huge difference on hills, passing, and accelerating from a stop. It eats up the southwestern PA hills, no problem.

I also raced that car (in pure street/pure stock classes) for a while and that gear swap alone gave me at least a tenth in the quarter mile. Combined with other simple mods (no power adders or cam swap), I broke into the 14s.

Engine does spin around 2000 RPM at highways speeds (75 MPH I think, pulling from memory here), so you will notice a slight MPG drop. But it should go up a little in the city and on the hills since the engine doesn't lug as hard.

My wagon is stock 2.56 and equally lethargic. Quite annoying compared to the snappiness of my sedan. I do tow with it, so eventually I will do the same swap on it. I have a set of 2.93 and 3.08 gears (and reluctor) ready to use from cars I've scraped, but seems silly not to jump to something steeper. It will depend on funds and availability at the time.

I can also vouch for a Detroit/Eaton TrueTrac. I run one of those too for several years. Best diff I've ever owned so far. Completely quiet, but aggressive. You need to be ready for both wheels to grab in rain or snow, tossing your back around much more than the stock Auburn LSD.
 

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Discussion Starter · #14 ·
Thanks for your help everybody - just about to order 3.42's with TruTrack from ClearImageAutomotive. Next, the PCM - I'll need speedo recalibrate, easier downshift (going off a street onto an on-ramp I have to almost floor it, or manually shift it, to get it to downshift) and air pump delete. Any recommendations for other changes I should get done to the PCM while I'm at it?
 

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Next, the PCM - I'll need speedo recalibrate, easier downshift
(going off a street onto an on-ramp I have to almost floor it, or manually shift it, to get it to downshift) and air pump delete.
Any recommendations for other changes I should get done to the PCM while I'm at it?
If the tuner is competent and thorough - I'll recommend pcmperformance.com atop a shrinking list of OBD2 LT1 tuners - any recommendations of the type that I would cover, would be handled without need to mention.

Put another way, for a standard mail-order tune from a reputable tuner, all you need do is mention your tire size & axle gear ratio for speedo calibration, plus a few other basics.
Any LT1 tuner worth a damn thoroughly and permanently disables the AIRpump's functionality.
Whether or not you physically delete it, IT WILL NEVER FAIL AGAIN.

Easier downshifts are also de rigueur; that is one of the fundamental reasons to ask for a tune.
Properly tuned, if you ever pull the shifter under 'OD' again, it'll be incredibly rare.
The tuned powertrain will respond less like it's trying to hold you back, and more like it appreciates your enthusiasms, without 'getting ahead of you'.

So far as PCM Performance is concerned, you fill out a form describing your car, powertrain, axle gear, tire size (not just wheel size!), thermostat, desired octane, 'personality' of tune, and any other changes you've made or you desire.
I'd imagine that other competent tuners would ask the same of any client.
 

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Did you build it, or did you have someone do it for you?
 

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Discussion Starter · #18 ·
Taking it to someone - I just... don't... have the nerve; watched lots of yooboob vid's on replacing gears but I know my luck. Besides, gear oil - ICKY! - and no hoist. And my CEL is on continuous for evap, and my mechanic does not like the look of my fuel tank straps. So, scheduled work this visit:

1) drop fuel tank, replace pump & sender, clean-up hoses out of the tank (we suspect one of those is the leak that's triggering the CEL); he's got the pump/sender and new straps already

2) while tank is out of the way, refurbish the axle - to include gears, Eaton Tru-Track, ABS reluctor (does anybody have the GM part # for a 3.42 reluctor? - unsure mine's the right one), axle bearings & wheel seals

3) look at the top of the diff and evaluate how rusty the brake lines are

4) new positive battery cable - mine had its end replaced, and has a bald spot >1" long; NICE thing to have on the positive cable!

5) safety check - it's up in September, mi'se well do it now

6) it has a "pop" in the pass-side front brakes; it pops when you step on the brakes, it pops when you take your foot off.

Points 4, 5 and 6 are optional for this visit; he figgers it'll take pretty well the whole day just to get the gears & tank done. I'm hoping the safety will be a few-minutes-and-new sticker formality; but I've seen a few disturbing indicators that the car may be rustier underneath than I'd hoped. There's nobody around here to trust it to for a frame-off resto; I've been watching a lot of Robby Layton on yooboob, and I'm really tempted to ship it down to Utah for his tender mercies, despite Utah being in another country and 'waaay more than half a continent away. Just so many things are casually available down south, that nobody's ever heard-of around here... :cry:
 

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1) drop fuel tank, replace pump & sender, clean-up hoses out of the tank (we suspect one of those is the leak that's triggering the CEL); he's got the pump/sender and new straps already
Make sure the fuel hose from the pump is rated for submersion in gasoline. There are plenty of people that assumed the aftermarket hose on the pump was correct, and ended up having to replace the hose shortly after when it failed.
 
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