Eaton fuller ultra shift plus transmission. changed clutch and truck no start an F on the read out along with Trans fingr gear and shft fingr rail.gear sensor and rail sensor no data link sometimes.

no VIN told
no country told
no year told
no kind of transmission told , manual or automatic
the only clue is 6th gear,
my 2008 jeep has a 6speed manual transmission
SEE?
let me guess it is a M./T box and has manual foot clutch
and the clutch slips.
seems your shop in town is not so good.

top cause of gears not selecting is the gear shifter linkage is all messed up. (damaged, worn, or adjusted wrong)
or the
main clutch is dragging (bad) or slipping worse.
any shop that knows M/t can diagnose it, but not yours.
the old 6sp mt box has side lever shift links up to 1995
then later the Eaton Fuller FS6406A 6 speed box?2004 up??>?? no year truck told, why must any helper beg fo the year.
with classical. top lever shift and big knob end
the bottom of the classical lever. has tip and this tip can be plastic to stop noise but wears out fast and the H pattern fails to work this is super common super easy cheap fix.
even a $10 fix.


Eaton fix easy, nothing ever was so easy this failure
see the stick?
remove it and see the tip is damaged.
bingo.will not pick gears in the H pattern, or is RAndom
BOX GOOD
CLUTCH GOOD
SHIFT TIP NOT GOOD. A DIRT CHEAP PART.

how many gears in this transmission remembering that Eaton make from 5 speeds up to 21 speeds in their range of transmissions
so if you have a 9 speed box and attempt to select 6 gear without using the range change you will be selecting probably first again
Don't assume that everybody knows what box you have so include all make , model year , equipment application in your posts as they are not linked

2 things; If you jack up one front wheel, stick it in gear, does it try and turn the engine? If it does then the trans is turning. Did you check the trans operated in all gears before you fitted it?

Next, is it possible the clutch friction plate is in backwards. If so then the raised side that holds the damper springs is hard up against the fly wheel and causing the drag that prevents the clutch from releasing.
I cant help with info as to whether the trans is a fit but while you are underneath the hood, look and see if the clutch arm appears to move the right amount when the pedal is pressed. The only other thing I can think of is that the trans is seized somehow. You can test this while its jacked up by starting up on idle with it in gear, the raised wheel will turn.. Try this in all gears but BE CAREFUL with it on jacks, better to have jackstands under both sides.

torque converter clutch shutter. lube guard makes a shutter fix. add this to your transmission fluid. see if that helps..

Not common. Being that it only happens in third, it is possible that the clutch is funtioning normally but your syncronizers might be shot. Or close to shot. Try double clutching to relieve some of the grinding. That means to shft from 2nd or 4th to neutral, let out the clutch then push the clutch again and shift to third. That was how old transmissions had to be shifted before we had syncronized transmissions. Not a very fast way to move. Or you might be able to skip 3rd whenever possible. I'm not sure abou tthe price of the tranny repair.

any transmission fault codes? this trans is electronically shifted so there should be a fault code for the problem, have it tested. Any Kragen or Autozone can run the test for free

the transmission fail safe is reverse and 2nd. gear.you probably missed reconnecting a large harness connector not near the trans but in the rear of the engine compartment. looc along the area behind the strut towers don toward the trans or right behind the engine.

Generally, what causes C-4's and C-6's to be slugish going into gear, is the seals on the servo pistons are getting hard. The servo pistons are what apply pressure on the clutch packs, when the seals get hard the oil can blow past the piston and the clutch won't engage. It's worse when the the trany is cold and usualy gets better as the oil gets warm. You could try some transmission conditioner, the cheep stuff works as good as the high dollar stuff. Don't rev the engine to try to get it to go into gear, the clutch is trying to engage and you will burn the clutch up pack. If the clutches were replaced 3k miles ago why didn't they put seals in it at the same time?

A clutch issue youtend to have more of an engagement problem with 1st and reverse gear for a small time period before you notice other gears.You want to check the clutch hydrolic system for any leaks(clutch slave at transmission,clutch master,which you look for leakage on interior above clutch pedal)and at fluid resevoir.you also want to double check condition of trans fluid. strongly recommend using only HONDA BRAND MANUAL TRANS. FLUID when doing maintinance,fluid should be replaced every 30k on this car.The Honda brand fluid is like night and day on these cars,it WILL make a difference in shifting!!TRust Me on this point! Sorry now back to your main clutch issue,when driveing and you go to shift gears and normally notice grinding,with clutch pedal in shft out of gear and before engageing it into next gear do a double pump of clutch pedal then see if when continuing to next gear if it engagees smoother.if so you know you have without a dout a clutch pressure plate/disc problem. I can tell you that in twenty years the only manual transmissions themselves that ever had problems were due to outside influences(gear oil in transmission,improper driveing,etc.)let me know what you find and we can go from there..JOEL

the fourth clutch is burnt probably due to a bad 4th clutch piston seal... if you can get a good trans that cheap then you should just put one in it unless you are familiar with internal trans repairs...