Speedo reads high- any thoughts?

[zaxcucv]

I did a search and see references to the speedo reading too low, but nothing on the speedo reading too high. Anyone have this problem and a solution? My speedo was reading about 80+mph while going 65 with the stock tires. Needle bounces a bit too. Now I have 33's on the truck, and the speedo is still off by about 10 percent on the high side. I have replaced the speedo cable, didn't help. Anyone have any thoughts? I've seen mention of lubing the speedo if it reads too low...would this help and does it require removal and disassembly of the unit? Because that is way beyond my meager abilities...

Thanks in advance.

 

[73m819]

could be the wrong speedometer drive gear in the transfer

 

[Goose2448]

could be the wrong speedometer drive gear in the transfer

 

[zaxcucv]

Thanks gents! Not to sound stupid, but why the heck would the military put the wrong gear in the tc??!!

 

[73m819]

because the old fiber one broke and this one FIT

 

[Goose2448]

I think you just need bigger tires

 

[Tanner]

...built by lowest bidder?

 

[zaxcucv]

All great responses... I'll do a search and try to figure out the correct gear and where to get it. What would account for the bouncing needle?

 

[Goose2448]

Mid 80s Chevy. Unless its REALLY bad dont worry about it. It might also tick, but that is normal.

 

[ramcatdoc]

My 85 M1009 does the exact same thing. 85 mph is about 65. 45 is 40, etc. The needle wobbles a lot at higher speeds. I therefore have no idea at all how far this truck has gone or what kind of mileage I get! I'm sure the odometer is reading too high, too.

My boys and I just say we are going "85 CUCV's per hour" (85 cph) and forget about it. I guess I could fix it, but I've gotten used to it. Don't think it's a tire thing, though.

 

[charlietango]

someone told me they did that because the cable gets crusty inside and catches, releases, catches etc etc.. not sure but sounds like it would make sense.

 

[wayne pick]

Yup, Mine does that catch and release thing too, The plastic jacketing is worn through where it's made contact with the body/ frame.

 

[wayne pick]

Tire size has everything to do with an inaccurate speedometer. Higher tires cover more ground per rotation than the stock tires. The speedometer gear in the trans is calibrated to the final drive ratio and the height of the stock factory tires. Mine is all wrong, 700r4+4.56 gears+285/16s=wacky speedo, 85 is actually 60, I checked it with my Tom-Tom GPS. I have also never seen a speedometer or fuel guage work right at the same time on any 80s Chevy trucks.

 

[combatmech]

I'm running 33's and my speedo shows about +5 of actual. Checked it with GPS....

 

[Bob H]

If it isn't bouncing, I'd say someone put a speedo drive gear from a 1008/1028 in there.
1009 = 3.08 gears
1008/1028 = 4.56 gears

 

[ammuscle]

I have the same problem with my M1009 does anyone know the right speedo gear to put in one to make it right?

 

[richingalveston]

I was under the impression that the trucks with the np 208 were the same speedo gear internally.
The 1009 has an adapter that changes the cable speed to account for the 3.08 gears. The actual gear in the transfer case is the same and interchangeable.
If it has been rebuilt by someone other than when in military this could have changed. If it is stock, the internal t-case gear is the same.
I believe the NP 205 output is same as np208 without adapter.
From what I understand, if you put a 205 in a 1009, all you have to do is move the adapter from the 208 to the 205.

If your 1009 is showing 15MPH +/- slower than your actual speed with stock tire, someone probably removed the adapter.

Tires are a big reason most are off. 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).

I am soon to have on the road a 1009 with 4l80e, NP 205, 4:56 diff and 39 inch tires. Speedo is going to be interesting.
Probably going to get the electric drive motor for the speedo that will connect to trans controller. I can then program the parameters.

Yes you can oil the cable, have to remove dash, bezel and cluster. Oil cable then put it all back. The cable however has no seal at the bottom so oil is temp fix.

Rich

 

[Mg84648]

Like Rich said above, shooting some Kroil down the cable will get rid of speedo bounce, worked for me

 

[ammuscle]

Ok, mine is unmolested. Running 31-10.50 with the 208 transfer but since I bought it I had to replace the speedometer cable since mine was broke it still ha the adapter on the end of the cable goin into the transmission but it reads about 65-67 to run 55 mph. Anyone tell me what gear might help get it close to actual speed?

 

[eme411]

Hi Guy's , all I can say on the speedo gears is read your parts books , lube your speedo cable ,on the speedo head it may need to be re-magnetised , remember these are 30 years old, or just buy a NEW speedo head from LMC,