hey guys i have a set of 3.73 gears sitting on my workbench, all i have to do is buy the install kit and put them in. you can see my mods in my sig. it will stay like this for about another 3 years till i graduate college and build my 383. however i have heard some guys say not to do this. they say 3.42 gears are better i have 3.23s and an open diff now but i have no traction problems. and my car isn't slow as i have suprised many a L98 owner and a few 5.0 stangs, so i don't forsee traction as being a problem. should i put the 3.73 gears in, or leave my 3.23 gears alone? if i do the swap what speedo gear do in need?

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86 IROC-Z
305 TPI
700R4 W/ shift kit
3.23 gears
T-Tops
maroon with gold stickers and rims/ black interior
43,000 miles
flowmaster exhaust, edelbrock headers, gutted airbox, converter, and MAF, K&N filters.

soon to come are 3.73 gears and subframe connecters.

 

3:42 will be best all around for mpg and acceleration. What motor do you have, if it's TPI they stop putting out power around 4500 rpm's and you'll run out of gear with 3:73's. That's why most people say go with 3:42's with TPI.

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'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
FLOWMASTER, NO CAT
EDELBROCK 600CFM CARB.
KN AIRFILTER
ACCEL HEI DISTRIBUTOR
160* Stat
3:73 Posi
Rebuilt 700R4 vette servo and .500 boost valve
B&M Megashifter, 5" Autometer Tach w/shift lite
Soon to be installed
3" Hooker Aero Chamber

 

yeah but lower gears will just make the motor get to redline faster. it will just give the engine a little more mechanical advantage. it will still shift at 5500 no matter what gears are in it, and it won't be spending any more time above 4500 rpm than it does now. and i certainly won't be topped out in the 1/4 mile so i don't see how it will harm me at all. any more opinions?


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86 IROC-Z
305 TPI
700R4 W/ shift kit
3.23 gears
T-Tops
maroon with gold stickers and rims/ black interior
43,000 miles
flowmaster exhaust, edelbrock headers, gutted airbox, converter, and MAF, K&N filters.

soon to come are 3.73 gears and subframe connecters.

 

I have basically the same question. I don't think anyone with a 700R4 has problems getting lots of torque in 1st gear. The problem happens when you hit 2nd gear and the engine bogs till you get some rpm happening. Wouldn't 3:73's cure this a little better than 3:42's?

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88 Trans Am 305 Auto Red/Silver, MSD coil,wires, ported plenum, gutted airbox, TB bypass, comp cams 08-408-8, everything else stock

 

3.73 gears would be pointless on your car unles you can rev to 7000 rpm. 700R4's already have a steep first gear, you dont need rear gears that high unless you need to rev high. your 305 probably pulls best around 3000-4500. With 3.73's you'll zip right through that in first, burst into second, and probably lose traction because of your shift kit, and you'll only be going like 30mph. I have 3.23 gears and if I hit 6000 in first, ill be going about 35. Imagine how short your first gear would be. I suggest 3.42 gears, or 3.23 gears, especially since you plan on putting a 383 in later on. both of those gear ratios will work well with a 383.

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1983 Firebird
TH700R4 Auto
Small Block 400
LG4 ECM, Intake, Carb, Distributor, etc.
Soon to be non-computer.
Clarion Head Unit 45X4
2 Pioneer 400W 12" Subs
Third Gen Performance
"A four cylinder is half an engine."
"Ponies can run, but birds can fly..."

 

Put the 3.73's in. You'll like them. I have them with a 700r4 in my 83. Don't listen to this Ward guy. They may not get you the most gas mileage but they are a lot more fun. I also had the 3.23's before I swithed.

 

I have heard time and time again that LB9's run out of steam at 4500...I dont know if I'm crazy, but mine seems to pull hard until 6000 and sometimes a little higher. I do understand the limits of the tpi system and why this happens...maybe its because I have the bigger 85 cam in there that I dont notice it as much...anyway, I would go with 3.42s personaly because of drivability issues, but I dont think 3.73s would make it slower than 3.42s. My guess is probably the same times for both gears due to wheelspin from the 700r4 first gear. You would probably do better with just a high stall converter than with the gears...just my opinion
doug

 

I just swapped out my 3.73 for 3.42. What Ward said is exactly true. In first with 3.73 in my 700r4 I would be lucky to hit 20mph then shift to 2nd and the tires would break loose unless I let off alittle for just a split second then she would grab and take off. The 3.42 are much more friendly although I can still burn second it takes alot more than it did and grabs much better than used to. Mileage is alittle better (19 with 3.42 - 17 with 3.73).

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87 Black on Black T/A
T-Tops Digital dash
5.0 TPI S/R Torquer 305 heads Summit TPI cam
204/214 @.050 .420/.442
SLP headers and catback
A4 with 3.42 gears
Fully loaded and everything usually works.

 

"Custman" did you have sticky tires? I was just wondering. Instead of putting the 3.42's back in I would try stickier tires. That just proves to me that your getting more power to the rear wheels to make traction a problem. "FlameRedMetallic" says that he doesn't have any traction problems.


"85transam" is on to something when he says high stall converter but the converter will just lauch you hard. To keep the car pulling after the launch you need lower gears.

I use the 3.73's and at the top of the 1/4 mile I'm just about ready to shift into O/D. I never do just let it wind up until I cross the finish line. And it's not 7000 RPM like some will say. It is somewhere between 5000 and 6000 RPM

 

Go with the 3.73's. I had 3.23 gears in my 83 and then I switched to the 3.73's. Man, what a difference! It will fry the tires off a straight punch and pulls a hell of a lot better. I also have a poopy LG4. But I seem to get moving the best when I shift at around 4800. I used to have an 89 GTA w/ a TPI 350 that was basically stock, and I shifted that at around 4500-4600. Stock TPI's dont like much higher than that.

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1983 T-top Trans Am. All stock (for now) LG4/auto/3.73 posi. 70,000 original miles. White w/ light blue int.

 

It's one of those win/loose situations.
I have a fully built posi 3:73 rear collecting dust. I choose to reuse rear that came with the car when I bought it 3:42 posi and this is a drag car.
Reason-traction. launch=smoke show.
I could just imagine the smoke show with that killer 1st gear in a 700r4. I used a turbo 350 with a 355 at the time at it would rip the tires no matter what. Hit it at red/yellow and hope it hooks up on green.
IMO 3:42 is the best all around gear choise yet if you want to impress the chicks at burgar king and since you have the gears go for the 3:73's.
Now my truck has 3:73 stock, and I would never change that because its a standard wide ratio 3speed and heavy enough to hook up.
Its all a matter of what works per aplication.
SSC

 

I just dumped in the 3.73's with the posi. I noticed that it will chirp the tires going into second, but when I'm at the track I never had a problem with it. Just make sure that you warm the tires up really well.

Mike

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1989 RS.. 355, Hypereutectic pistons, double roller cam, double roller timing chain, accel wires, blue streak cap and rotor, rapidfire plugs, chevy caprice 350 chip, 200* fan switch, 3 angle valve job, 3 inch cat-back exhaust, 3 core radiator, 3.73 gearing with POSI.

 

thanks for all the info guys, sounds like the jury is still out, but i'm still leaning toward doin it maybe. and just keep my 3.23s and put them in with a posi when i get my 383 built.(in like 4 years :-( ) i just want something to make my 305 a little nastier off the line. as i stated before, i don't really have a traction problem now, should i develop one after the swap i can always play with my tire pressure and put some rubber snubbers in my rear springs, and some simple stuff like that to help, but as of now this sucker hooks. it has 245/50/16 BFG radial TAs and they stick pretty good for me right now. thanks again for the help, and any other suggerstions are greatly welcomed! i want to hear opinions!


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86 IROC-Z
305 TPI
700R4 W/ shift kit
3.23 gears
T-Tops
maroon with gold stickers and rims/ black interior
43,000 miles
flowmaster exhaust, edelbrock headers, gutted airbox, converter, and MAF, K&N filters.

soon to come are 3.73 gears and subframe connecters.

 

In their "My Generation Camaro", CHP's biggest gains were when they went to the 3.73's. If that gives you traction problems, the solution isn't that tough (poly busings, boxed or tubular LCA's, lowered LCA mounts, etc.). Also check the "Stroke in the Desert" articles on the mag articles link - he went 3.73 as well.

7000 rpm's to make 3.73's worth it? Ward, you can't be serious!

SSC, want to get that 3.73 posi out of your way?

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. 2-1/2" cat-back, ZZ3 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/'87 LB9 block, ZZ3 cam, ported World 305 heads, Hooker 2055 headers, 3" Catco cat & 3" cat-back, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

 

When I had a similar setup, I had to bump into overdrive to finish the 1/4 mile.

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Mark Lock
- 86 IROC-Z - SuperRammed 383/T56
- -= IROC Online =- - The site dedicated to the IROC-Z

 

Just thinking....
If you do go ahead and change to the 3.73's and the gearing is too short for your taste and drivability, you could always go with a taller tire to make up the difference, couldnt you?
just a thought

 

i hope 3.73's arent that bad i just put them in ,in place of the 2.73 rear that came in it stock. i wanted 3.42's to be honest but, for 120$ for the entire 3.73 rear..........i couldnt pass this up hope they work ok goood luck to all.

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89 firebird formula


360 10:1compression (350 .060 over)/fully balnced and blueprinted
comp cams xe262 cam
performer rpm intake/port matched to heads
#1405edlebrock 600
sportsman 2 heads 64cc 2.02/1.60 valves 200cc intake runner/cnc pocket ported
msd 6al/msd8.5 super condutor wires
h.e.i. proform 50,000 volt vac. advance ditributor
700r-4 with 3.08 first gear and 3.23 posi 7 5/8 rear end.
b trans shift kit(will kill shifts...suck dong!!)
shorty heddman hedders with custom 3" pipe y-pipe back(no damn cat!) with 40 series flowmaster!
griffin daul1" core rad.cutom fabrication to fit(but no cutting )


future mods: 406 roller REALLY REALLY REALLY RADICAL!!!!!.with lots of NOS