High RPM's is something wrong?

Ok another probably stupid question from one of the new guys.
66 cj5, 350 chevy, 4 speed tranny Should I really be doing 5100 rpm's at 55 mph or do I have a problem somewhere?
Yes tranny is in 4th and transfer case in high... I doubled checked just to be sure! lol

 

What is the axle ratio? Are you sure the tach isnt set to "4 cyl, or 6 cyl"?

 

It depends on your gear ratio, and tire size. Sounds like you have extremely low gears. I bet in low range 1st gear it really crawls huh?. Check your differential for a tag, if it doesnt have one you have to open it up and count the teeth on the ring gear and the pinion gear and do some division. Most manufactures print a division numbers on the ring gear to make it east for you. Hope I have helped

 

5:38's and 30" tires might do that

 

Yea we need more info, what size tires and find out what gear ratio you have in your axles. Also like mentioned above are you sure that the engine is actually runnning that fast. Cause if you have a 350 that is running at 5100rpm to do 55 its gonna sound like its about ready to come unglued.

 

I'd check the tach setting first. I have a 350 in my jeep and a 3spd tranny with 5:38's and 55 mph tachs out at 3500 rpm.

 

Thanks all for the help, below is what I know .. or don't know at this time!
1. gear ratio ... I have no idea but I am pulling the covers off this evening and will check. I pulled teh drain plug on the transfer case last night and MILK came out so I figured i better check the pumpkins as well.
2. Tach setting .... I didn't even think about that, teh tach was installed when I got the jeep and I just hooked it up when I dropped the 350 in it. PO didn't have it hooked up just installed in the dashboard so that may be the problem.
3. Motor sounded like it was winding up prettty tight but dang sure not like it was doing 5100.

Thanks a million for the tips I will know more this evening.

 

Let us know for sure. I am curious...

 

I'm betting the tach is set wrong. PO probably had either a 4 or 6 cyl in the Jeep, and set the tach accordingly.

 

I pulled the tach out and there is nothing to set, the only thing there is a choice between hooking it up 6v or 12 volt so I imagine that is teh problem.
I took the covers off and both diffrentials were full of water so I am letting it drip out now.
I didn't get around to counting teeth (tag was unreadable) but the gear is stamped 10 8 65 DANA 18525 A3D27 44-9
I am guessing the 10 8 65 is the date but couldn't make sense of teh rest of it and a web search didn't turn up anything useful.

 

you have 4.88 gears. the last 2 numbers 44-9 is the ring then pinion tooth counts.

 

Good call Jeff, you beat me to it. It is definately the tach. Like I said, I have the 5:38 gears in mine with a 350 and a 3 spd and only run 3500 @ 55mph. I'd spend the $45.00 on a new tach.

 

Well once again yall came through for me.. THANK YOU.
No wonder the po didn't have the tach wired in! lol

 

If I'm not mstaken the 44-9 means you have 4:88 gears.