Guest Posted September 20, 2003 Share Posted September 20, 2003 I don't really have any knowledge of speedometers other than disconnecting the cables. I changed my rear end ratio in my 71 from 2.73 to 3.42, 12 bolt posi on a 350/350th car. Now I'm going 72 mph on the speedo when I'm doing 55. How do I correct or calibrate my speedo? Thanks. Quote Link to comment Share on other sites More sharing options...
Guest Posted September 20, 2003 Share Posted September 20, 2003 Ok, Andreas posted a site on an earlier post which pretty much explained the process. Doesn't sound too complicated providing you don't have to change the internal gear in the tailshaft. ANYWAY, has anyone here changed ratios from 2.73 to 3.42 on a TH350, and how many teeth did your new speedo gear have to have? Quote Link to comment Share on other sites More sharing options...
dbreese Posted September 20, 2003 Share Posted September 20, 2003 Pyro I went from a 2.73 to a 3.36 and took my car to a shop that had a set of speed calibrated rollers. They went to a light blue 45 tooth which I think was the largest they could get and got the speedo within 2 mph at 55/70 and at 90 it was off by 3 mph. The odometer was off by 1/10 of a mile and they said to get it right on they would have to change the drive gear in the tailshaft so I just left that alone. Hope this helps as a starting point for ya. David Quote Link to comment Share on other sites More sharing options...
Andreas Posted September 20, 2003 Share Posted September 20, 2003 This should answer all your questions: http://members.core.com/~faldrich/speedo.htm ------------------ 71 Monte 454 HO 5- Speed "FULMNTE" 01 Camaro V6 Andreas' Monte Carlo Site Member NMCOA, FGMCC (Event Coordinator) ------------------------------------------ ------------------------------------------ "It ain't a car if it's not a Monte" Quote Link to comment Share on other sites More sharing options...
busmechanic Posted September 21, 2003 Share Posted September 21, 2003 Pyro Did you notice a good amount of change on take off and how much rpm's are you running at 55 mph that is if you have a tach. Quote Link to comment Share on other sites More sharing options...
Guest Posted September 21, 2003 Share Posted September 21, 2003 There's definitely a noticable change in launch and acceleration. I'm running 2500-2600 rpm at 55mph. Not bad at all. I debated over 3.42's or 3.55's. I don't think it would have made a tremendous difference either way. Quote Link to comment Share on other sites More sharing options...
FullMonte Posted September 21, 2003 Share Posted September 21, 2003 Pyro, Did you add the posi at the same time you changed the gears, or did you already have the 12 bolt. I am interested in the cost of changing my stock 10 bolt to a posi with better gears. George Quote Link to comment Share on other sites More sharing options...
Guest Posted September 21, 2003 Share Posted September 21, 2003 The car already had a 12 bolt, but I added a posi. I used Strange gears and an Eaton posi. Go to "gears are us", do a search, I don't know their web address. I did a lot of shopping and they had the best price anywhere. You'll need a posi, gears, and a master bearing kit. Plus you'll need a couple hundred bucks for the install. Don't have the total of what I spent right off hand. Quote Link to comment Share on other sites More sharing options...
MeanMonte Posted December 6, 2003 Share Posted December 6, 2003 I still havent changed my speedo yet but when i went from 2.73 to 4.11 even though i also installed a 700r4 my speedo reads around 90 at 55 hahhahaha Quote Link to comment Share on other sites More sharing options...
Guest Posted December 6, 2003 Share Posted December 6, 2003 pyro, this would be a guess ,but i would say you would need to swap the gear at the end of the cable to about 4 more teeth,more teeth on the cable gear slows down the speedo .(if i remember correctly)that gear is about 9.00 through chevy.iwould try that for the 9.00. gene Quote Link to comment Share on other sites More sharing options...
Guest Posted December 7, 2003 Share Posted December 7, 2003 Actually, I had to change the ones inside the tailshaft and at the cable, but it was really fairly simple. Quote Link to comment Share on other sites More sharing options...
kc8oye Posted December 16, 2003 Share Posted December 16, 2003 'eh? gear on the end of the cable? what's this? the only speedo gears I know of are inside the tail housing.. Quote Link to comment Share on other sites More sharing options...
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