700R4 WITH OD???
Thread Starter
Burning Brakes
Joined: Feb 2001
Posts: 841
Likes: 0
From: Wichita, Ks, USA
700R4 WITH OD???
My car has the 700R4 /OD RPO but i never see the OD light on the tach come on. The other day i was cruising at 80 -- 21-200 rpms and getting 17mpg. If i slowed down mpg would go up. Wouldnt this be the time for the OD to kick in? Im not sure I understand how it works or why it wont. whats going on? TIA
Drifting
Joined: Dec 2000
Posts: 1,733
Likes: 0
From: Sarasota FL
Re: 700R4 WITH OD??? (Jsailor24)
When my shift lever is in OD the trans will shift upto OD at about 45mph. The torque converter locks up at about the same speed if there is low load. I usually leave the lever in D until I am doing a steady 55mph to avoid lugging the engine. GM CAFE score makes them too conservative in their tunings. Its the same situation with the manual guys and that idiot CAGS, that makes them box shift from 1st to 4th.
Your mpg sounds right to me also. The computer uses the vacuum signal and throttle position to compute the average.
Your mpg sounds right to me also. The computer uses the vacuum signal and throttle position to compute the average.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Re: 700R4 WITH OD??? (Jsailor24)
Overdrive light??? I must be missing something. The 700R4 is a 4 speed automatic, with 3rd gear being 1:1 and 4th being an overdrive (.70:1). Your rpms/speeds sound like everything is working properly. Next time you are going to be going over 50 or so, count your shifts. It should shift 3 times, plus the converter lock up.
Team Owner
Joined: Sep 2001
Posts: 62,143
Likes: 1,729
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Re: 700R4 WITH OD??? (Jsailor24)
I dont see your problem. Its acting just like its supposed to, if youre in OD then youre in OD, it has already kicked in if youre doing 80 at 21-2200rpm. Once you go over 45-47mph with the shifter on OD, then youre in OD (unless youre flooring it)
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: 700R4 WITH OD??? (DON M)
The computer calculates mpg by integrating the injector pulses and dividing that into miles obtained by integrating pulses from the transmission speedometer sender. It does not use vacuum and throttle position.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Safety Car
Joined: Dec 1999
Posts: 4,691
Likes: 1
From: Framingham MA
Re: 700R4 WITH OD??? (Jsailor24)
The OD light does come on in the auto, but it indicates you need to upshift. If you drive your car on the highway in "drive" or have a slipping 3-4 clutch in the tranny, the OD light will come on.