Click Here!

Go Back   IH PARTS AMERICA > Tech Forums > Basic Tech Questions
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read Photo Gallery IH Store Home

Thread Tools Display Modes
Old 08-09-2017, 03:45 PM   #1
Join Date: Jul 2017
Member Number: 8771
Location: NJ
Posts: 36
Default Broken Speedo

Finally got my truck plated and registered. I am so happy, and it came back from the mechanic who said WOW this is a cool bad ass truck that runs perfect. Just had some oil filters and fuel filters changed, and the carb dialed in. Drive it home and noticed the speed didn't seem accurate.

Any ideas of which parts I would swap out to make it work again? I have not dove into my service manual of 1500 pages
Attached Images
dmf6978 is offline   Reply With Quote
Old 08-09-2017, 04:27 PM   #2
Senior Member
Join Date: Oct 2008
Member Number: 624
Location: denver
Age: 39
Posts: 258
Default Re: Broken Speedo

like it seems to be showing to slow to fast?
the needle bounces?

this is a new problem ? or has been a problem for years ?
int77345 is offline   Reply With Quote
Old 08-09-2017, 04:32 PM   #3
Join Date: Jul 2017
Member Number: 8771
Location: NJ
Posts: 36
Default Re: Broken Speedo

No bouncing. But it said I was going 25-30 but I felt maybe going 35-40. Just bought the truck and had it tune up. First time actually driving it today. I will keep an eye next time I drive using my gps and get a better feel of actual speeds. Good news is I found parts to,replace just in case.
dmf6978 is offline   Reply With Quote
Old 08-09-2017, 09:27 PM   #4
Senior Member
FDChappie's Avatar
Join Date: Aug 2011
Member Number: 3742
Location: The State of Jefferson
Posts: 1,460
Default Re: Broken Speedo

Checking it against the mile markers on the side of the highway will help calibrate it.
1974 Scout II 345 T-19
1971 Travelette 392 T-36
1972 Loadstar 1700 dump truck 345 T-35
FDChappie is offline   Reply With Quote
Old 08-09-2017, 09:37 PM   #5
Scoutboy74's Avatar
Join Date: Apr 2008
Member Number: 453
Location: Daze Crick, Jefferson
Posts: 3,701
Default Re: Broken Speedo

That's good news on the overall health of the truck. A misreading speedo is small potatoes by comparison. You can stick your Tom Tom Naggigation deevyse in the winder and compare notes. Larger than stock tires can throw things off. A speedo cable that hasn't been well lubed in the last three decades can throw things off. Or your speedo gauge itself may just be ready to go ta-tas up.
Favorite hobby...Driving Salma Hayek in my Scout

Coal Trickle - '99 Dodge Ram 2500 Q-Cab SWB 4x4 - 5.9L 24V CTD/NV4500
Hooty - '74 SII - 392/TF727/D20/3.73 D44's/Spartan FA/Krac-lok RA/RC 4" SUA/34x10.5 TSLs/33g Fuel/HFT 8k winch
Mongo - '71 1210 Std Cab 2WD - 345/TF727/RA17 D60 4.10 Trac-lok - "Mongo love candy! Duh, huh, huh!"
Scoutboy74 is offline   Reply With Quote
Old 08-10-2017, 05:29 AM   #6
Administrator & Owner
ihpartsjeff's Avatar
Join Date: Jan 2007
Member Number: 1
Location: Grass Valley, CA
Age: 43
Posts: 4,010
Default Re: Broken Speedo

I use a GPS app on my Iphone to check speedometer accuracy. If the speedometer is indeed off and needs to be corrected, we offer these inline speedometer gear boxes that will correct it.

Speedometer Calibration Gear Box - Corrects your Speedometer!


Jeff Ismail
IH Parts America - Owner
IH Sierra Fall Rallye Event Coordinator
CPT - Crawler Proven Technology
ihpartsjeff is offline   Reply With Quote
Old 08-10-2017, 04:03 PM   #7
Join Date: Jul 2017
Member Number: 8771
Location: NJ
Posts: 36
Default Re: Broken Speedo

Very cool. What exactly does that part do? Does it come with instruction? I suppose I can remove my cable now and check it out, make sure nothing is frayed. can i lube it somehow?
dmf6978 is offline   Reply With Quote
Old 08-11-2017, 06:40 AM   #8
Senior Member
1975IH200's Avatar
Join Date: Dec 2008
Member Number: 731
Location: 3rd to last cave on the right
Posts: 471
Default Re: Broken Speedo

It is a small gearbox that goes inline with the speedometer cable.
You put different plastic gears in it to correct the speedometer to match the tire size & final drive gearing you have installed on the truck.

Usually one can go to a speedometer repair shop in town where they put your vehicle on a roller and run the drivetrain up to speed and see how far off your speedo indication is.

Then they either change the gears in your box or if your truck does not have one, they build a box with the correct gears in it and install it on your cable and then the speedo reads correctly.

Although these trucks were built during the heyday of NASA, their is no rocket science in them.

My Junk --> 1975 "200HD" AWD Truck
My Cave location --> Western North Carolina
1975IH200 is offline   Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

All times are GMT -8. The time now is 05:45 PM.