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79 G20 Gauge Cluster
#808559 November 30th 2023 12:05 pm
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Sidecar Offline OP
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Good morning, fellow Vanners. I recently bought a used gauge cluster for my rig, which is reading 15 mph lower than the one I removed. I'm not sure why that would be; it looked and hooked up like the old one. Any suggestions will be greatly appreciated.


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Re: 79 G20 Gauge Cluster
Sidecar #808562 November 30th 2023 2:06 pm
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Hey Sidecar, Welcome!

Probably something to do with speedo/tire size calibration in the unit. Never had to mess with it inside the speedo, regear the drive or what not. IDK about the newer stuff. If it is programmed or what. An instrument man would know!

Van on!!


BBC Blue
1990 Chevy G30 L19 7.4 EXT
Church Van, maternity division

DogVan
1988 Dodge B250
LA series 318 Wedge 5.2 TBI A500

Cabin Cruiser
'94 Dodge B350 www.xplorermotorhome.com/
Xplorer MH model 230
230 hp LA series 360 Wedge MPI 5.9 A518 OD auto

Old vans are getting pricey!
Re: 79 G20 Gauge Cluster
Wedgy #808572 November 30th 2023 9:52 pm
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The one I bought from Ebay is identical to the one I took out. I cannot believe Chevy made these clusters different. My opinion is one cluster is made the same as any other and should work the same way. To replace gears in the transmission output shaft to make it work correctly seems unthinkable


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Re: 79 G20 Gauge Cluster
Sidecar #808582 December 01st 2023 9:53 am
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Back in the day, I believe the gears were in the speedo assembly itself. Kinda Ike changing jets in a Holley carb.

IDK know how they do modern cars for different sized tires for speedo correction. What year is your Van? I have a couple1980's 1990s Gvan factory parts manuals.
Good question 🤔 Instrument men!! Chevy guys!!!


BBC Blue
1990 Chevy G30 L19 7.4 EXT
Church Van, maternity division

DogVan
1988 Dodge B250
LA series 318 Wedge 5.2 TBI A500

Cabin Cruiser
'94 Dodge B350 www.xplorermotorhome.com/
Xplorer MH model 230
230 hp LA series 360 Wedge MPI 5.9 A518 OD auto

Old vans are getting pricey!
Re: 79 G20 Gauge Cluster
Sidecar #808593 December 01st 2023 8:05 pm
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Not sure what transmission you have but if one of the TH’s (350 or 400) but a different size wheel & tire combination along with the incorrect speedo gear in the trans can easily cause the incorrect reading on the speedometer….there are calibration charts on the internet just put in your tire height and rear end gear should tell the correct speedo gear you need to use in the side of the trans…..


Recently purchased (10-2021) a 1991 Chevy G-20 “Shorty”. Past vans are a 1976 Chevy G-10 (purchased new in 1976 & sold in 1995). A 1978 Chevy G-20 Shorty purchased in 2010 and sold in 2015.
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Re: 79 G20 Gauge Cluster
soundhd #808594 December 02nd 2023 8:50 am
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Originally Posted by soundhd
Not sure what transmission you have but if one of the TH’s (350 or 400) but a different size wheel & tire combination along with the incorrect speedo gear in the trans can easily cause the incorrect reading on the speedometer….there are calibration charts on the internet just put in your tire height and rear end gear should tell the correct speedo gear you need to use in the side of the trans…..

Awesome information that I never knew. lol
And I have a TH400. :)I guess I got lucky with the electronic S10 cluster that was smoking🔥flying down the off ramp to straight into Escondido Auto Electric 😲 grin lol


Great stories. Useful information! Where? On vanning.com
Van on!


BBC Blue
1990 Chevy G30 L19 7.4 EXT
Church Van, maternity division

DogVan
1988 Dodge B250
LA series 318 Wedge 5.2 TBI A500

Cabin Cruiser
'94 Dodge B350 www.xplorermotorhome.com/
Xplorer MH model 230
230 hp LA series 360 Wedge MPI 5.9 A518 OD auto

Old vans are getting pricey!

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