Speedo and temp gauge

[montytw]

I'm new to the forum and to CJ's as well. Bought a '83 CJ7 Renegade that is in good shape. Thought I could use it to learn some things. It has a 4 speed manual Transmission and straight 6. Currently it has a new set of 33 x 10.50 R15LT tires on 15" wheels. I noticed the speedometer reads about 15-20 miles per hour slower than type actual speed as measured by a GPS smartphone with speedo app. I read some of the posts on here with similar problems and they suggested new speedo gears. I have a friend who rebuilds race cars and I'm going to ask him to look at it tomorrow. Sound like where I need to start?
(2) The water temp gauge is inoperative but the heater is blowing out plenty of warm air. The engine runs fine. No overheating. Next step to check would be? I like all the gauges to be operative even though I use this jeep mainly intown. Sorry if questions seem a bit dense. I suspect I'll learn plenty as I go. Thanks. Tom

 

[007]

Hey welcome!

My guess on the speedo would be that it's been re-geared. 33s would make a difference but not sure of a 15-20mph difference.

Stock temp gauges are not great but check wiring and check sender to start.


Sent from my iPhone using Tapatalk

 

[Jsooter]

Welcome!

x2 on checking your temp sending unit. Mine barely moves off of cold, yet blows hot air out the vents. I bench-tested both the fuel and temp and they function correctly, so my next step will be the sending units.

 

[Saddle Tramp]

These are from a 1977 service manual but I think the temp/fuel gage is the same for your year. Note the connection between the two gages.

 

[Torxhead]

Learn as you go is about it! Your vehicle came with a lot smaller tire than it has now and the speedometer gears are not turning as fast due to the larger tire. The speedometer gear in the Transfer Case can be changed to correct this. If you changed the differential gear ratio to compensate for the tire change that would correct your speedometer also, plus give it more pep. John Strenk's new gauge page on the net has quite a detailed rundown on CJ gauges to help you out.