68 Bucking Bronco -- 4-high acts funny

[bralston]

I bought a 68 bronco a few weeks ago and the 4-high doesn't act like I expected. When I shift my bronco into 4-high and try to drive, the vehicle bucks like I'm just learning how to drive a standard, even when I shift from first to second or third. All gears buck with full gas and the clutch fully disengaged. All the other gears drive fine, 2H, 2L, 4L all work great. But 4-high the vehicle's front axles seem almost geared low or something, when I shift into neutral it doesn't seem to coast to a stop but stops almost immediately. It also popped out of 4 high twice. It shows James Duff on the shifter knobs, but I don't know if the tranfer-case/transmission are anything other than a normal 68 model. There isn't any funny noises or anything.

Any advice is greatly appreciated.

Brad

 

[Skiddy]

Sounds like you might have different gears in the front than the rear. How fast have you drove in low if pretty slow might not have noticed.

 

[broncnaz]

If the front axle was geared wrong it would do it in 4L also and if on a hard surface you would probably blow the tcase up. Might be time for a Tcase rebuild have you checked the oil lately? I'd drain it to see whats in there. Bearings or gears could be wornout. You might also want to check for any other play in the driveshaft and axles as if theres enough play that could make the gear ratio between the front and rear be off enough to bind up.

 

[bralston]

Huh, so that's why 4-low works but 4-hi seems kinda like 4-low ? 4L works all around but 4-H bucks in every gear at 5+ mph.

 

[Skiddy]

If the front axle was geared wrong it would do it in 4L also and if on a hard surface you would probably blow the tcase up. Might be time for a Tcase rebuild have you checked the oil lately? I'd drain it to see whats in there. Bearings or gears could be wornout. You might also want to check for any other play in the driveshaft and axles as if theres enough play that could make the gear ratio between the front and rear be off enough to bind up.

Yeah the more I think about that sounds more likely. It could be a gear in the transfer case maybe missing some teeth.

 

[Broncobowsher]

Try the gear ratio check in the tech articles. leave the hubs locked and the T-case in 2WD.

Also go through and check the U-joints (especially the front axle) and make sure all the needle bearings are still in there.

 

[bralston]

I checked everything in the transfer case, replace gear oil and transmission gear oil (it's a 68 model) checked all the ujoints. There was no problem anywhere. It is very clean, no shavings, missing teeth any thing.

 

[wildbill]

Sounds like you might have different gears in the front than the rear. How fast have you drove in low if pretty slow might not have noticed.

This is what I would think is your problem you need to check it out. If it is stock it will be 3:50 rear and 3:54 front and or 4:11 rear and 4:10 front check them real close as someone mite stuck a 3:25 in the rear or something. good luck. Bill %) ;D

 

[stlkikn]

Had the same thing happen in a 77... almost locked right up!!
Turned out the spud screw holding the low range shift fork had loosened off.
First, check to see if both shift rails are moving when the t case is shifted. If they are, take the inspection cover off the t/case again. Have someone else shift the t case through the gears with 4 low being the last, then shift it out of 4 low into neutral.
If the front output sliding gear is NOT moving, you have found your problem.
Good luck.

 

[Pa PITT]

I had the same problem the other day....i went to the back of my place to play around in the mud 4h seemed ok until i got back on dry hard ground ....then mine would not shift out of 4h so i limped it to the house on the grass ...
put it in the shop jacked it up off the ground it seemed to pop real loud and then it would come out of 4h and the wheel unlocked ....
mine seem to need more room for the shifter to get into gear ..i'd just done a lift and forgot to check the shifter travel..next trip out it seems ok after i cut
little more travel on my shifter...