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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: JBerryhill on April 02, 2009, 08:25:29 pm

Title: What is this thing?
Post by: JBerryhill on April 02, 2009, 08:25:29 pm

I tried searching for this but came up empty, I was under my truck today and noticed an "L" shaped gear drive on my tranny speedometer cable (1987 GMC 700R4) and was wondering what its called and whats it for. I was going to disconnect my cable to see what color speedometer gears I have. I went from a 2.73 to a 3.42 now my speed shows 15mph over actual speed. Anyone seen this part before? Thanks for any help, Jerry

Title: Re: What is this thing?
Post by: Unofficial on April 02, 2009, 08:34:20 pm

I think I know what you're talking about. All that thing does is allows the speedometer cable to stay straight instead of bending at a 90 degree angle, as far as I know. I had to inspect my speedometer cable and gear, and I had to pull that thing off. I don't know what it's called though.

Title: Re: What is this thing?
Post by: ccz145a on April 03, 2009, 08:51:55 am

I believe it is to correct the speedometer reading, just one more way to do it without messing with the speedometer output gears. Take it off and put you cable to the trans and see where your speedometer reading is, then go from there to correct as you started to.

Title: Re: What is this thing?
Post by: duckynme on March 14, 2010, 09:51:17 pm

It's called a speedometer cable adapter, just a right angle adapter to get the cable pointed toward the front of your truck.  There's one on my t400 in my 77 one ton dually crew cab.