Okay I have 88IROC 305TPI A4 with bolt ons. I have all the pieces to go 3:42 from 2:73.

I want your experiences, such as:
How did it feel off the line
Was it a worthwhile mod/experience

I understand all the power band theories, just want some info from those that have been there. Thanks

 

I did that exact swap in my 74 Caprice 454 convertible, 2.73 to 3.42. I've also done a few 3.23 to 3.73 swaps.

Either way, it felt like I just bolted in about 15-20% more horsepower. Not something I regretted, that's for sure.

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"So many Mustangs, so little time..."
ICON Motorsports

 

Considering everything I did as far as upgrades to my car screamed for a lower gear, I noticed a night and day difference in acceleration when I went from 2.77 to 3.42 gears.

Do the swap, you won't be dissapointed.

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1987 GTA L98 MD8
355, TFS Heads, LT4 Hot Cam
My GTA

The Minnesota F-body Club

 

I went from 2:73s to 3:73s. I had to end up buying a use posi because something in the old rear broke, spyder gears or something like that. Anyway with parts and labor it came to $600. The car is quicker off the line and my mpg doesn't seemed to have suffered, but I wish I wouldn't have done it, I just don't feel $600 worth of acceleration. But that's just me, most people will tell you definately go for it, I just wish I would have waited since I just started college and money is tight.

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"Rice burners are like tampons...Every pu$$y has to have one"
'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
3" Hooker CatBack w/Aero Chamber muffler
EDELBROCK 600CFM CARB.
KN AIRFILTER
ACCEL HEI DISTRIBUTOR
160* Stat, just switched to 180* b/c of winter coming and going to college in the mts.
3:73 Posi
Rebuilt 700R4
B&M Megashifter, 5" Autometer Tach w/shift lite

 

Thanks for the replies.
I have the parts for the swap and I think I'm out of bolt-ons. I think it will be fun. OHH the mechanic will set my gears for $100 and he has done many cars. It's a go.. thanks again

 

Why not hit up the guys in Motor Pool or the local DS or GS Maintenance unit?

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1987 GTA L98 MD8
355, TFS Heads, LT4 Hot Cam
My GTA

The Minnesota F-body Club

 

Army mechanics are not known for setting up gears. Replacing batteries maybe? Also these gears are going into a rear-end that's off the car, the one that will have 98+ brakes.

 

Hey now....... me = 63W20

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1987 GTA L98 MD8
355, TFS Heads, LT4 Hot Cam
My GTA

The Minnesota F-body Club

 

I don't know yet but I'm about to find out myself...Need Rear End Advice...got 3.42 Zelex-Torsen...will it kill mpg and the tranny?

The short version is I bought 3.73 auburn for my T/A....since the T/A is a M6 now I have a spare 3.42 Zelex-Torsen.

My Camaro has the 2.73 gear open diff in it now. If I swap in the 3.42 rear how much gas mileage will I lose? How much 1/4 mile time will I gain.

The car dyno'd 132rwhp and 220rwtq but it has 225,700 miles on the original tranny. Will the new rear add strain on the tranny and kill it?

 

63W20 is that heavy equipment?
I'm just kiddin about the mechanics, but I have been at the mercy of 63B for 10 years, some good some bad. In the reserves?

ARTIC WHITE...your trans will not suffer from the gear swap. Gas mileage might be slightly lower, very slightly. But you will gain
1. Traction from the posi carrier
2. More torque/snap off the line.
Note: I have seen cars gain 1/2 sec in the quarter from this swap(gears,traction)

 

I swapped a 9-bolt 3.45 posi for my original 2.73 open diff. It pulls off the line much better. It won't kill your tranny. But don't forget to swap the speedo gears.

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90 RS Convertible
Owner: Top-Down Solutions
(626)369-0040

http://www.sc3gfb.org/members/lonsal.html
http://www.taskerinc.com/gs3/profiles/Lon_profile.htm

 

63W = Wheeled Vehicle Repairer. We do all wheeled vehicles but we do a higher level of work than a 63B does. They are Motor Pool personnel and only do light bulbs and tire-change type stuff. We do all the real work like pulling and replacing engines and driveline componants in DS units, and rebuilding those failed engines and driveline componants in GS units. We do it on all wheeled vehicles from M998s to M977s. Yeah, I am in the reserves for now...... until I get the phone call!

Laterzzzzzz
Good Luck - Hooah

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1987 GTA L98 MD8
355, TFS Heads, LT4 Hot Cam
My GTA

The Minnesota F-body Club

 

Thanks again for the replies. What speedo gear color for the 3:42s.
Hey GTA I spent most of my time on the M93 FOX, ever work on one? I'm a 54B. I guess you can build a small block blindfolded.
Also my rear-end(car) has 145K on it.

 

You can't go wrong with the 3.42 and a 700 IMHO. Great off the line and you still cruise at @2200 at 70. I just redid my tranny W/3.42 gears and I think that the speedo gears were 15T drive and 41T driven.

[This message has been edited by transfixleo (edited October 11, 2001).]

 

The speedo gears are as follows for 3.42 gears and a TH700R4 (those are GM part numbers):

15T Drive (8642620) Gray
41T Driven (25513048) Yellow

I don't know about building a small block blind folded..... that's pushing it..... hehe. I haven't worked on an M93 FOX and to tell you the truth, I am not sure what one is! Also, what is a 54B? I don't think I have ever seen what that is either.....

Laterzzzzz

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1987 GTA L98 MD8
355, TFS Heads, LT4 Hot Cam
My GTA

The Minnesota F-body Club