The Stovebolt Site Forums The Parking Lot Big Bolts SPEEDOMETER ADAPTER

Does anyone know where I can find parts to repair or a new adapter for the speedometer on my 48 GMC for the 2 speed rear end. The one I have has a vacuum leak and it looks like the rubber diaphragm has dry rotted. Just wondering if anyone ran into this and had any suggestions. Thanks

Give the folks at Spedometer Solutions a buzz, they seem to be pretty capable folks. Whenever I get my finances in order I'm sending them my gear reduction adapter and cable for repairs.
http://www.speedometersolutions.com/

Thanks I'll look into it

on my gmc i tried to replace the diaphragm by using a piece of innertube. problem is the tube is too thick and i couldnt get it to work. i ventured into getting the proper material and over time i decided to just leave it alone. on the chevy they used or at least on mine they used a linkage rod that went from the shifter to the adaptor. i messed with that one too and left it alone. since i know my speeds and what the the speedo reads i just make a mental adjustment in my head. it was too much effort for so little to gain. the only time i am concerned with the speed is in hi gear hi range. which both are about 50 mph.

I use my old GPS unit to tell me the speed I'm driving. The maps in it are out dated but the speed reading is dead on. Save a few bucks and go with the GPS unit until you get exactly the part you need or want.

Just my 2 cents...

I do the same thing actualy. I also use the trip time and milage feature for paid hauling jobs.
As far as repairing the existing diaphram with an innertube section, you CAN do it, but it should be a lighter type of tube like a bicycle tube (I used one to repair a 1940's oxygen regulator from a Mustang fighter plane, it held up to 50,000 feet in the test chamber too). Just have to find the right thickness of material and dont make it too tight so it has room to throw the mechanism.

i used a 20" truck tube. no bicycles here