Jumpy transfer case clunk (1 Viewer)

[Bighim]

Gentlemen, need some tech help. I have a 76 fj40. When I engage the transmission into 1st there is a clunk just as there is a load on it. I had my friend move the truck forward and backward while I looked at the driveshaft goes into the transfer case and it appears to jump and clunk at the same time. This issue can be heard going through all the gears (1-4 and reverse). All the fittings are greased appropriately as well as the u joints. To me being a novice it seems to be at the transfer case. Any help will be appreciated.

 

[Sig191144]

B,

I have the same problem. Maybe we can both get some help here.

c.

 

[shawnfj40]

You need to make sure that the whole case isn't loose. If its not you might need to pull the shaft and make sure which end is the culprit.

 

[Living in the Past]

Try moving the driveshaft by the hand brake on the back of the transfer case to see if there is any play. If just the driveshaft moves problem is in the back of the transfer case. Could just a matter of a loose nut on the transfer case output shaft or rear bearing. If the whole transfer case moves you have other problems. If nothing seems to have any free play open the hood and see if the whole engine moves when you put it in gear. If it does problem could be a bad motor mount.

 

[Pin_Head]

If it just clunks when you put it in gear, the clutch may be dragging and needs adjusting.

If the clunk is due to engaging the clutch with the transmission in gear, then there is excess slop somewhere. The drive shaft is easy to check. Just turn it and jerk it around and look for slop in the U joints and slip joint. 4sp trannys are known for wear on their output shaft where the input gear rides. If the splines are worn then you need a new used tranny with a good shaft.

 

[Bighim]

I have checked the driveshaft for free play and it seems tight as it should be. I will check to see if the whole engine moves when I put it in gear. The mounts on visual inspection look good. Any other ideas are welcome.

 

[Bighim]

Any more suggestions?

 

[Pin_Head]

The wear on the tranny output splines is a well known problem that causes a klunk when accelerating and engine braking, but you don't want to hear that.

 

[Bighim]

Does this require a transmission rebuild? What is the best way to approach the repair?
Thanks Ed

 

[Pin_Head]

It requires removal of the transfer case and inspection. You want to rule out everything else first. Do you have any slop in the differential? Do you have an autolocker?

The way to check for spline wear is to remove the clutch cover and the PTO cover on the transfer case and jack up one rear wheel with the transmission in gear. They use a large pry bar or wrench to turn the drive shaft back and forth while you observe the transfer input gear and flywheel teeth. If you can move the input gear back and forth without (excluding the normal easy turning gear backlash) the flywheel moving, then the shaft is worn. How many degrees it turns depends on how worn.

 

[Bighim]

I did put a new nice 3rd member in recently and still have the issue. I will try as you described and see what I find out. Your expertise is invaluable.

 

[Living in the Past]

I had my friend move the truck forward and backward while I looked at the driveshaft goes into the transfer case and it appears to jump and clunk at the same time.

Have you ever verified that the drive does jump and just making a clunk sound? Did it make the sound when your friend was releasing the clutch and made noise just before moving? While it takes another gasket I would just remove the cover on the back of transfer case that cover end of the transmission. With the transmission in gear and the transfer case in neutral I would hold the nut on the back of the transmission and see how much the input gear will move with no movement in the nut on the back of the transmission output shaft. Any movement is the play between the output shaft on the transmission and input gear (angle cut gear inside the PTO opening) for the transfer case. That takes everything else out of the equation.

 

[Sig191144]

Man, really not liking what I am hearing. I have felt for a while now that a transfer case inspection, rebuild, replacement is order.

Thanks all for the input and for letting me piggyback on this thread.