Re: jeep T-18, pops out of 4th gear? alot
The problem of popping out of fourth gear can have many sources. Alignment with the engine is often the cause, the input shaft must run true with the crankshaft if it is off center or at an angle the maindrive gear will have an orbital motion that will cause the sliding clutch to walk back off of the drive lugs. A dial indicator affixed to the flywheel should be used to check the bellhousing pilot bore and rear face to see if it runs true. the transmission front bearing retainer should be checked to see if it mates snugly in the bellhousing. If every thing checks good, then the only thing left is wear on the main drive gear and sliding clutch drive lugs, if the sliding clutch is bellmouthed on the flanks of the splined area that engages the blocking ring and main drive gear this will cause it to jump out of gear, (this type of wear is usually caused by poor transmission alignment, that is why i reccomended checking alignment first).
good luck, jjc