Speedometer does not read actual speed... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

68gmsee · 08-04-2007, 09:35 PM

I have a 68 GMC with a stock 250. Some year ago I removed the 3 speed non synchronized trans for a synchronized one that came off a V8 truck.

I found out my speedometer is 10 mph off!!! Shows 20 mph and it should be 30 mph and 25 mph and it should be 35 mph (measured with another newer vehicle). Don't drive it much and usually on country roads. Also, I usually drive slow but I'm lucky I haven't been caught speeding.

I read where they make gears to fix this, but can't find out where to get them.

Any help appreciated.

08-04-2007, 09:35 PM	#1
68gmsee Active Member Join Date: Jul 2007 Location: Centrally located between Houston, Austin and Waco. BCS area. Posts: 7,947	Speedometer does not read actual speed... I have a 68 GMC with a stock 250. Some year ago I removed the 3 speed non synchronized trans for a synchronized one that came off a V8 truck. I found out my speedometer is 10 mph off!!! Shows 20 mph and it should be 30 mph and 25 mph and it should be 35 mph (measured with another newer vehicle). Don't drive it much and usually on country roads. Also, I usually drive slow but I'm lucky I haven't been caught speeding. I read where they make gears to fix this, but can't find out where to get them. Any help appreciated.



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