92 nissan pickup can't figure it out

[Hardbody007]

So I have a 92 nissan pickup 4x4 it starts up and runs fine works great though all the gears but 5th it like shutters / vibrates since issue the things that have been fixed are new driveline old one was bent - all new rear spring bushings - tune up everything - new trans mount - checked the rear diff - rotated the tires - checked the timing it's right at 10deg where it should be. The problem only happens in fifth at like 45-50 mph any higher or lower it's fine shifter don't shake but goes away when the clutch is pressed in iam thinking now it's the clutch but has anyone ever had or seen this issue any help would be great thanks

[Hardbody007]

Also checked and cleaned the maf sensor and did check the egr valve just by taking the vacume line off it still sucks even plugged the line and drove didn't make a difference

[Hardbody007]

Oh and one more thing also found 2 broken vacume lines fixed them didn't make much of a difference

[Adverse Effects]

look at what speed it happens in then go that speed in 3rd 4th and 5th see if it happens each time if it dose it has to be after the gbox if it dosent its the gbox or clutch/flywheel

[Hardbody007]

Ya don't happen in any other gear at them speeds just fifth and goes away when clutch is depressed is it possible the the clutch or flywheel are out of balance ? I guess there's no way to check unless it's pulled out

[Adverse Effects]

if it was clutch or flywheel it would happen at a set rev range something like

1St gear 4000rpm = 25Kmph
2nd gear 4000rpm = 50kmph
3rd gear 4000rpm = 75kmph
4th gear 4000rpm = 90kmph
5th gear 4000rpm = 110kmph

thos numbers are not correct but just to show what i meen

so its not at a set speed in any gear
and its not at a set rev range in any gear

but only in 5th and only at 45 to 50 mph

that is an odd one

if it did it in 4th as well as 5th at 45 to 50 mph i would say wheel balance or bent axle or tail shaft or uni joint or something like that

but it id did it an any gear when the motor was spinning as a set amount of revs then i would say clutch or flywheel or an imbalance in the motor

[Hardbody007]

Ya that's what's buggering me up I wanna say the clutch but it should do it in more gears but i mean at 5th doing 45-50mph the truck is moving fast and not much torque or load on it so if something is imbalanced like the clutch or harmonic balancer on the engine it would probably show itself