Topic: 3.70 or 3.73 gearing
in Forum: C3 Driveline Components
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I want to change the rear differential gear from a stock 3.08 to 3.73 in preparation for adding a tremic TKO 600 5 speed with a .64 5th gear. A local shop is telling me the correct gear would be 3.70 and not 3.73. I know this is not much of a difference but isn't there only one correct answer to this question. If so which is correct. Thanks for the help.
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The factory gear ratio would be 3.73...aftermarket gear sets may be a slightly different ratio. Either will be pretty much the same, and either will fit the housing. SO...if all that is available for your year/housing is the 3.70, then that's what you can use with no problems. 
Joel Adams
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Lifetime MemberApache Junction, AZ - USA
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Vette(s): 1982,150K,Renegade CFI,Hooker Side Pipes,85 fuel pump,Bilsteins,HD suspension, Aluminum radiator, SharkBar/w 5-Point Restraints. 3:73 gears coming soon.
I'm going to install a 3.73 differential this winter - most everyone I talk to says 3.73 is too much...... Let us know how you like it.
Phill's Vette 2009-09-05 12:36:44
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My differential recieved a factory replacement set of 3.70s. I think that ratio was standard for a while.
LukesVette 2009-09-05 14:13:34
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Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20218
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Paul(LukesVette) caught my typo...the 3.70 was factory...
Still, there will be no discernible difference in the two gear sets, except possibly on a loong road trip. The 3.70 might give ya a wee bit better mileage, but prolly not enough to make a big deal. You also won't be able to feel any difference in take-off grunt between the two ratios.
Still, there will be no discernible difference in the two gear sets, except possibly on a loong road trip. The 3.70 might give ya a wee bit better mileage, but prolly not enough to make a big deal. You also won't be able to feel any difference in take-off grunt between the two ratios.
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Vette(s): 1979, Targa Blue (72 Color), Pace Car rear spoiler, L88 hood, Dark blue factory interior, 525HP 406, HD 700R4, 370 gears,Steeroids, composite rear spring, TT IIs wrapped in T/A Radials.
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[QUOTE=Phill's Vette] I'm going to install a 3.73 differential this winter - most everyone I talk to says 3.73 is too much...... Let us know how you like it.
[/QUOTE] On an '82 the 3.73 may be too much. The 700R4 trans has a 3.08:1 first gear (very low) and with a 3.73:1 rear you will be thru 1st gear in about a 1/2 second. I have 3.55:1 rear gears and they are fine, still goes thru 1st in a heartbeat. This only applies to the '82.
[/QUOTE] On an '82 the 3.73 may be too much. The 700R4 trans has a 3.08:1 first gear (very low) and with a 3.73:1 rear you will be thru 1st gear in about a 1/2 second. I have 3.55:1 rear gears and they are fine, still goes thru 1st in a heartbeat. This only applies to the '82.
Dave
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Vette(s): 1982,150K,Renegade CFI,Hooker Side Pipes,85 fuel pump,Bilsteins,HD suspension, Aluminum radiator, SharkBar/w 5-Point Restraints. 3:73 gears coming soon.
yeah, that's what I'm hearing. If I don't like it, I will rebuild the original differential with 3:55 and sell the 3:73.
Thanks Dave!
Thanks Dave!
[QUOTE=Phill's Vette]
I'm going to install a 3.73 differential this winter - most everyone I talk to says 3.73 is too much...... Let us know how you like it.
[/QUOTE]
[/QUOTE]
With the overdrive in the 5 speed I am planning at 70MPH the RPM's will be 2078 which should be OK with my mostly stock 300HP motor. If anyone has any opinions about RPM ranges at highway speed I'd love to hear them. The reason I'm changing the rear end is raise the highway RPM at 70 MPH from 1824 to something a little higher.
in Forum: C3 Driveline Components
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