Speedo reads high- any thoughts?

[Crash_AF]

On my 1009 I went and got the proper speedo gear for the transfer case so that it would be correct, I have no need to maintain 100% interchangeability between a 1008 and 1009. As for the cable, spray some kroil or other lube down the cable, then pack the top of the cable head with grease, gravity will do the rest as the shaft spins to work it down. I've seen the military adapter wear out and get out of calibration as well.

Later

 

[Hasdrubal]

33's on all stock CUCV's with either t-case will make your actual speed 10mph lower on the speedo at 65. (speedo accuracy +/- of 5mph). Yes you can oil the cable, have to remove dash, bezel and cluster. Oil cable then put it all back. Rich

My 1009 runs 33's, speed is off 4 km/h, that's 2.5 mph. Going by all the photo radar readout panels around town. I lube my speedo cable twice a year to prevent the dreaded needle bounce syndrome. I've never taken all that off. Lie underneath dash and reach up, grab speedo cable, run hand to end where it attaches to back of speedo. There is a clip that must be depressed to release cable. I do it with one hand, can be tricky for the dexterously challenged but you can do it with 2 hands no problem. Then bring cable out and under the dash opening. Using needle nose pliers, grab the plastic drive end of cable, pulling it out about a 1/4 inch. This allows better access to the casing hole, then using a can of spray grease with a long spray extension, insert into casing hole and give it a a blast. Installation is easy, bring cable back up and around wiring to back of speedo, the drive boss sticks out, simply push cable back on and it snaps in, Very quick job.

 

[Drock]

My 1009 runs 33's, speed is off 4 km/h, that's 2.5 mph. Going by all the photo radar readout panels around town. I lube my speedo cable twice a year to prevent the dreaded needle bounce syndrome. I've never taken all that off. Lie underneath dash and reach up, grab speedo cable, run hand to end where it attaches to back of speedo. There is a clip that must be depressed to release cable. I do it with one hand, can be tricky for the dexterously challenged but you can do it with 2 hands no problem. Then bring cable out and under the dash opening. Using needle nose pliers, grab the plastic drive end of cable, pulling it out about a 1/4 inch. This allows better access to the casing hole, then using a can of spray grease with a long spray extension, insert into casing hole and give it a a blast. Installation is easy, bring cable back up and around wiring to back of speedo, the drive boss sticks out, simply push cable back on and it snaps in, Very quick job.

This does work! I just finished it. It is ah little fiddly but now that I've done it once, I'm an expert. I was having the same problem as the OP , but it only started after I installed my gear venders unit. In the morning when the truck was cold it would get up to about 65MPH and then go haywire. Hopefully this solves it.

 

[scottladdy]

On my 1009 I went and got the proper speedo gear for the transfer case so that it would be correct, I have no need to maintain 100% interchangeability between a 1008 and 1009. As for the cable, spray some kroil or other lube down the cable, then pack the top of the cable head with grease, gravity will do the rest as the shaft spins to work it down. I've seen the military adapter wear out and get out of calibration as well.

Later

Any chance you still have the part number(s) to share? I'm certain others will benefit. Thanks!

 

[Westech]

When I I stalled M1009 axles under my M1008 I I stalled the blazer speedo adapter on the transfer case. All was fine until I installed 33"tires.
To fix the spedo I took off the clear cover of the dash, pulled the needle indicator and then used my GPS to drive 45 mph and as I was I installed the needle. It's off 1 mph at 60 mph. I think that is close enough.

 

[Crash_AF]

I have the GM parts book for 1984 C/K trucks. I'll see if I can find it.

I think there was a website that listed which gears went with which rear ratio and sold them... I'll dig through my bookmarks and see if I can find that too.