79 L48 Speedo Question
Thread Starter
6th Gear
Joined: Sep 2020
Posts: 6
Likes: 1
From: Radford, VA
79 L48 Speedo Question
Hello,
I have recently acquired a 1979 C3 with the L48 engine option. The speedo gauge has a face that shows 0-140MPH. I think the L48 had the 0-70MPH gauge, if I'm not mistaken. I'm wondering if the prior owner swapped the gauge; was there an option for a 140MPH speedo with the L48? My wife was pacing me at 55MPH (her car speedo) and the corvette showed about 70MPH. The trans and differential look to be unmolested. On Ecklers, they show a speedo conversion service, leading me to think that the L48 and L82 gauges can't be swapped without some extra work - if you want it to display your actual MPH. I'm wondering if the awesome folks on this site can confirm the gauge differences.
I have recently acquired a 1979 C3 with the L48 engine option. The speedo gauge has a face that shows 0-140MPH. I think the L48 had the 0-70MPH gauge, if I'm not mistaken. I'm wondering if the prior owner swapped the gauge; was there an option for a 140MPH speedo with the L48? My wife was pacing me at 55MPH (her car speedo) and the corvette showed about 70MPH. The trans and differential look to be unmolested. On Ecklers, they show a speedo conversion service, leading me to think that the L48 and L82 gauges can't be swapped without some extra work - if you want it to display your actual MPH. I'm wondering if the awesome folks on this site can confirm the gauge differences.
Last edited by 79JOE; Sep 8, 2020 at 05:50 PM.
Race Director
Joined: Mar 2017
Posts: 11,953
Likes: 4,509
From: Virginia
You can get a GPS speedometer app for your phone and do the experiment yourself at a few different speeds. There is a gear that can be replaced at the end of the cable where it goes into the transmission. Does your 79 have cruise control? It is possible that your rear differential gearing was changed, or your transmission.
Thread Starter
6th Gear
Joined: Sep 2020
Posts: 6
Likes: 1
From: Radford, VA
Super helpful - thanks! My particular car was prior to the depletion of the 140MPH speedos. I must have something else going on. I can now focus on chasing other potential causes.
Thread Starter
6th Gear
Joined: Sep 2020
Posts: 6
Likes: 1
From: Radford, VA
You can get a GPS speedometer app for your phone and do the experiment yourself at a few different speeds. There is a gear that can be replaced at the end of the cable where it goes into the transmission. Does your 79 have cruise control? It is possible that your rear differential gearing was changed, or your transmission.
Melting Slicks
Joined: Sep 2004
Posts: 3,227
Likes: 670
From: Northeast
Through the GM Heritage you can get a copy of the original invoice for $50 if that interests you. http://www.gmmediaarchive.com/?page=1
And here is a great pdf file with specifications you can download:
https://www.gmheritagecenter.com/doc...t-Corvette.pdf
And here is a great pdf file with specifications you can download:
https://www.gmheritagecenter.com/doc...t-Corvette.pdf
