When driving in 5th gear should the RPMs run at 3000 RMPS. Mine is a 4 cly 5 speed

there is not enough specif details available to be able to be close to exact But I will give an example that you can compare
in a manual transmission with a diff ratio of 3.909 and in 5th gear the rpms for 79 mph is 3200 rpms
the difference between gears is around 250 rpms so if you try to correlate the differences if it was in 4th gear the rpms would be around 3750 rpms so I suspect that the over drive section of the transmission is not engaging ( assuming that it is auto transmission)
so to answer your question , I am saying that it is too high in rpms for that speed and I suspect that the od is not being engaged as the rpms at 80mph I would be looking at around 3200-3500 rpms depending on the diff ratio

It is impossible to calculate with out knowing the over drive ratio (5th gear) and the diff ratio and tire size but with most vehicle with 5 speed boxes it should be in the 3000 to 3500 rpms range
The average vehicle at 74 miles/hr or 120 k/h runs around 3200 rpms
it doesn't matter how many cylinders or if 4x4 or make of vehicle , the rpms is tied to the ratio of the gear and the diff and the circumference of the tires
Sorry , it cannot be more exact than that

The only thing that comes to mind is that in 5th, the rpms may be so low that you are running on low speed potion of ignition module, getting weak spark and not burning fuel properly. This could be true in all gears at low rpms, but you would not notice it as much because you probably keep the revs up more in lower gears. Just a thought.

That is a typical RPM at that speed for most 6-speed 4 cylinder engines. The reason for this is that they have a much lower power output at lower RPMs (due to lack of torque), and the engineers want for you to have SOME acceleration to get up little hills.

old car. 5th gear? is this M/T? 1987 ?
A/T? is 4speed

what does stopped working mean .
1: shifter fails to select 5 gear H pattern slot.
2: grinds?
3: cant force it to 5th with clutch depressed.? is free play at spec?
4: raise front wheels off ground, can you get in to 5th now? keyout and running?
5: can you get into 5th parked engine off, and select 5th and then start car in 5th with clutch depresses first step. then slowly very slowly attempt to move car starting in 5th, but dont finish, just feel the gear, feel that its there and not neutral.

not working ,says nothing at all.

2,500 to 3,000 on a 12 yr old car. Newer vehicles with 6-9 speed auto transmissions sometimes run as low as 2,200. But your gearing is your gearing. Can't change that now.

Sounds like 2nd gear in the transmission is slipping. Cars usually shift at 15-20 mph from first to 2nd. First check the trans fluid.

Sure you can, It just makes the engine work a little harder. As long as your not running down the road at 3000 rpm's all the time, it will be fine

check clutch for slipping condition,mayb due to worn clutch disc or a oil contaminated disc or a weak pressure plate not locking disc to flywheel therefore giving u a slipping condition and higher than normal rpms

Mine has a high pitched whistle at high rpms and I can't figure it out. But mines def not the tranny. I'm thinking it's a vacuum line somewhere. It's a 97 2.3l manual. The colder it is the louder...