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You will have to change the speedo drive gear in the transmission. It's very easy to do. Just disconnect the speedo cable from the tranny, the loosen the retaining bolt that holds in the 'bullet' that the cable screws on to. Remove the 'bullet' and the plastic gear. Go to your local chevy dealer and tell them that you need a gear for a '78 Vette with your specs. You'll need you trans type, rear gear, and rear tire specs. Be sure to ask for the '78 and not the '79. I tried to get one for a '79, and since some of them came with the 85 mph speedo, they gave me the wrong one.
BTW - I'd get new O-rings for the gear and bullet while I was at it. It's always a good idea to change them while it's apart. I think there about $0.10/ea.
From: Exiled to Richmond, VA - Finally sold my house in Murfreesboro, TN ?? Corner of "Bumf*&k and 'You've got a purdy mouth'."
CI 6-7-8 Veteran
CI-VIII Burnout Champ
St. Jude Donor '06-'10, '13
Re: 140 mph speedometer for 1980 (e3pres)
nope nope nope....
You just have to get a speedo that is made for the 1980 that displays up to 140 MPH.
There are several vendors that sell them, Zips for sure, but I know there is one that sells them ultra cheap and I was just about to post asking for the contact info.
I think the guy is called "tic tock doc" or there was another called redline gages or something like that.
Yep, you got it. UKPaul put one from Redline Gauge in his '81. E-mail him with questions about it. I plan to do the same one of these days... :rolleyes:
Thanks for all the advice. I called Redline and ordered the speedometer. What a great price. They are even going to set the milage to the current milage on my old unit... all for $56 dollars.
From: Manchester, Dead Center in the Middle of TN 25 miles to Jack Daniels,10 miles to Geo Dickle, and .8 mile from the Liquor Store at I-24 Exit 114
St. Jude Donor '05
Re: 140 mph speedometer for 1980 (Jmccreary)
The speedometer is magnaticly calibrated. The only difference is the numerals on the face. Red Line will do you an excellant job. They actually used the factory face the last time I talked to them.
The speedometer gear in the transmission is calibrated to the rear ratio and the if rear ratio is being changed it requires a transmission gear change, but
the speedometer 85 or 140 MPH is not a "Special" gear. http://www.redlineg.com
JM:
Glad to see you ordered the speedo. I'm happy for you.
I've had mine for over a year, and I love it. Best upgrade/ investment yet.
What a difference a vendor can make. Let's see:
$56.00 for a working functional speedometer from Redline, vs. $90.00, for two hunks of carpet called floor mats, from any of the larger vendors.