Help with correcting speedo (gear)

[Prospect62]

Guys I have 35" tires and stock 3.08's on my M1009. Yeah it sucks but a gear swap ain't happening anytime soon.

Can anyone tell me what speedometer gear for the NP208 I need to correct the speedometer? Right now I think it reads too fast, meaning it says I'm doing 50 when I'm really doing like 30 but I haven't taken exact speed measurements. The truck is up on jackstands now anyway until further notice.

Basically I'm wondering if somebody who did 35's with 3.08's could tell me which gear they used and how they went about it. I did some research and got so confused between drive gears, driven gears, etc etc etc my head hurts.

I know not many M1009 owners here are lifted on 35's, just throwing this out there lookin for some direct advice. Research has lead to nothing but more confusion. Thanks.

 

[Barrman]

It should be the other way around. Reading slower than actual speed. Is the speedometer reduction box on yours?

The plastic gear on the output shaft of the NP208 and the plastic gear that goes into the NP208 are the correct ones for all the other CUCV trucks with 4.56:1 gears. Just the M1009 got the reduction box.

Which means you can find a different reduction box and screw it in. I looked for the proper one to get and realized the cost was going to be around $150 to get one and gave up that idea.

The other option is to change out the two gears. Dropping the drive shaft, removing the tail shaft and filling the NP208 full of fluid again are part of this process. I stopped once I got a very stead and dependable 10% slow reading at all speeds after a new cable and lubricating the speedometer itself.

I would suggest CK5.com as a place to get the exact part numbers and colors for the proper gears if the answer doesn't show up here soon.

 

[Prospect62]

It should be the other way around. Reading slower than actual speed. Is the speedometer reduction box on yours?

The plastic gear on the output shaft of the NP208 and the plastic gear that goes into the NP208 are the correct ones for all the other CUCV trucks with 4.56:1 gears. Just the M1009 got the reduction box.

Which means you can find a different reduction box and screw it in. I looked for the proper one to get and realized the cost was going to be around $150 to get one and gave up that idea.

The other option is to change out the two gears. Dropping the drive shaft, removing the tail shaft and filling the NP208 full of fluid again are part of this process. I stopped once I got a very stead and dependable 10% slow reading at all speeds after a new cable and lubricating the speedometer itself.

I would suggest CK5.com as a place to get the exact part numbers and colors for the proper gears if the answer doesn't show up here soon.

It might be the other way around, I honestly can't remember. I've driven the truck 1/2 mile since I've owned it.

I'll have to get under and take another look for the reduction box.

Where did you find the appropriate reduction box?

 

[Barrman]

Everyone that has done an axle swap on a M1009 has a reduction box sitting around. I am sure one will show up for sale.

 

[Barrman]

Just remember the box is meant to get the speedometer within 3-4 mph plus or minus with 31” tires.

 

[Prospect62]

Just remember the box is meant to get the speedometer within 3-4 mph plus or minus with 31” tires.

Probably not going to be sufficient to correct for 35's then. I'm OK with changing out the speedo gears themselves it's just such a complicated soup of gear options I was hoping someone could provide some clarity on which would be appropriate for my tire/axle combo.

Not a huge priority either way. I'm sure some day, if I keep this thing, a re-gear will be in order.