I have a 700R4 in a 86 IROC with 2.73 gears right now but when I put my 355 in I want to go with 3.42 or 3.73 gears but don't want the engine to scream. About half of my driving is a 75 mph. I have 245-50/16 tires. What do you guys run for RPM with these gears?

Thanks,
Mark

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1986 IROC LG4 "Bone Stock" (for now)

 

I have 3.73s (stock with the L69 option); my car's RPM is about 2900 at 75 in 5th. It would be slightly lower with a 700 in OD and lockup, maybe 2700-2750.

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

 

3.73's with overdrive 2150 at 60mph.
2550 at 75mph.

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82 camaro--original steering wheel, brake/gas pedals, seats--everything else modified
82camaro

[This message has been edited by 82camaro (edited May 02, 2001).]

 

3.73 at 70mph with 245/50r16 for me is almost exactly 2500 rpm in OD- slightly less with my new 255/50 tires. this is a 700r4 in lockup. If i could do it again i would have gone with 3.42 because it is a better all around gear, especially for a tpi car. If you are keeping the tpi i think the car would be faster with a higher gear and you'll get better milage.

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'88 RS (originally 2.8)
-350, .040 over, vette alum. L98s, stock tpi.
-305 injectors & chip
-TES headers & edelbrock cat back
-3.73 gears, 700r4.
Best with 2.8-17.4@77mph
Best with 305-15.0@93mph
Best with 356-13.7@101mph
on a 2.050 60 ft.
(Damn the 2.8!)

[This message has been edited by '87FAKE-IROC-Z (edited May 02, 2001).]

 

Figure out what MPH you should be Running in the 1/4, at the end Via HP estimates...

Then Figure out what gear would give you that MPH at your power peak, at the trap...


That Should Give you a pretty decent stab at the best performance gear, Now that has nothing to Do with Highway.

I plan On installing 3.42 On mine, Good all around gear.



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60 Ranchero - Project ( Money Hole )
85 Sport Coupe LG4 - Daily Driver
Reader's ride -> My Ride

Just another Hot Rod kid, or thats what they all tell me.
Livin' the Stereotype

 

I have 3.42 and 65 mph I am about 2100 RPM's. I get about 25mpg when i run about 85-85MPH. Huge performance gain and i find the car drives much better.

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91 Z28 Camaro
305 TPI
Flowmaster 3" exhaust
700R4 with 2000 Stall and shift kit
One sweet sounding system

 

Thanks for all of your inputs. I think I am leaning more towards 3.42 gears since I do time on the highway. I guess that would still be a great gain over my 2.73 gears!

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1986 IROC LG4 "Bone Stock" (for now)

 

huge improvement.
10.47:1 overall first gear ratio with 3.42's
8.35:1 overall first gear ratio with 2.73's
Around here the speed limit is 55-60 on the highways, so 3.73's/locker work great for me. If you don't have posi, a powertrax locker would be a good addition. Deeper gears can result in traction problems.

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82 camaro--original steering wheel, brake/gas pedals, seats--everything else modified
82camaro

 

I like my 3.73 gears way better than the pos 3.23 gears that every one likes. I get better traction with my 3.73 gears and as far as my 5th gear vs. 4th in my old 700r4 do the math because the t-5 has a much taller over drive.