High/Low gear shifter slips in to neutral on the Highway

[ktmkirk]

I have had on sevearl occaisons the High/Low gear shifter slip in to neutral while driving down the highway. I'm not sure what would cause this and if it is something I just need to watch or if there is an adjustment. I was thinking about getting a strap or something to "lock" in the shifter in High when I do find myself crusiing down the highway. I have also had to replace the cable recently that goes to the rear differential which broke soon after I picked up the vehicle, when it did the same kind of thing of going into neutral. Any ideas? Kirk

[David Dunn]

Kirk
That cable goes to the t case shift linkage. Release the linkage and make sure the lever goes all the way into gear (both ways). It may be that the cable isn't adjusted right ( and hopefully you didn't mess up inside the case).

My old 712 broke because the linkage was frozen. Make sure the joint is flexible.


Dave Dunn

[ktmkirk]

[quote="David Dunn"]Kirk
That cable goes to the t case shift linkage. Release the linkage and make sure the lever goes all the way into gear (both ways). It may be that the cable isn't adjusted right ( and hopefully you didn't mess up inside the case).

My old 712 broke because the linkage was frozen. Make sure the joint is flexible.


Dave Dunn[/quote]

Thanks Dave, the reason my original cable broke was beacuse it was froze up too, I'll check the adjustment and hopefully that is it. It doesn't do it all the time just when I'm on the road for a period of time like the vibration makes it want to slip in to neutral.

[David Dunn]

Kirk
Release the linkage and put the t case in one gear, then have someone move the shifter towards that gear and make sure there is enough travel, then try the other gear... Hopefully your cable was "only" adjusted short of having hi range fully engaged, and flexing of the drivetrain disengaged it. I use "only" as in no other damage done.
Dave Dunn

[lindenengineering]

You might want to consider an inspection of the input flange and shaft at the T/case input, (should the cable appear to be shifting the selector shaft from detent to detent.)

Any perceivable "end float"of the shaft will cause jump out due to the fact that the syncho assy is located on the input shaft. There are a set of shims found under the step register if the front input oil seal housing to control bearing preloads. It is permissable to remove a shim "or two" to control end float.

Should you tie the selector lever into high range to prevent "jump out" you will accelerate wear on the bronze selector shaft trunnions since they will be in overload contact within the gear sliding dog.

The only way to correct the problem should wear be present on the gear dog teeth is to tear the unit down and replace the items affected. Beware they will be expensive, and as a foot note the sychro cones (baulking rings) are now made in sintered iron and not bronze so no problem with that GL4/GL5 connundrum.
Dennis

[Jim LaGuardia]

If adjusting does not work, then the T-case will have to come out for repairs.
A common ailment is a broken syncro lock spring. When this part fails the sliding sleeve waggles, end result is replace the 3 springs, the sliding sleeve, and the High input gear
The excessive waggle of the sleeve causes the mating teeth to wear, resulting in loss of gear range
Hopefully it is just a cable adjustment

[David Dunn]

Now, now, stop with the negative vibes, think positive..... its just an adjustment

[Lightningpinz]

I hope it is just an adjustment. Al Fink of RMP fame in llieu of adjust or checking the t case shifter added a turn buckle to hold the shifter in place at freeway speed. He finally lost the bearings supporting the shaft and required a tow from Nevada to Denver and then got the EXPENSIVE bill to replace shaft, bearings and was it a case half Dennis? The end result was the old Fram advertisement Pay me now or pay me later. Check and adjust NOW it not able to adjust, REPAIR now!!!!

[lindenengineering]

Yes , that repair was expensive since no-one had a used t/case available so we had to make one from parts we had on the shelf.

That activity was more than three years ago, then the Hi gear pinion was $850, the Lo was $1230, the rest was chump change at about a $2500 for a reclaimed case and sundries like a mainshaft and drive gear.

Although important the cost is outlined to illustrated the need to take care of this sub assy which is (or at least can be) extremely expensive to fix if it grenades on the highway. (towing for Al's truck was $1600)

Just a footnote, for those of you who do DIY a T/case repair be carefull on dismantling and reassembly of the case halves. One RMP member "individual who shalt remain nameless" broke his case halves when trying to force them together with the fixing studs.
Another tip is to load the case to assimulate the "crush condition" it experiences being loaded into the drive line arrangement.
Experiments have shown that a considerable mainshaft preload can exist after insertion within the drive arrangement to cause premature failure of mainshaft bearings or even seizure causing parent case journal wear!
Yes we do have a fix to recover that by the way, and it doesn't involve welding. That activity (highly skilled alum stitch welding) incidently usually results in case distortion dictating a line boring/sleeving adventure. In either case it all adds up to money out of your pocket or the Anglo American perpetuation of "revolving debt" (credit cards).
Take care
Dennis
Linden Engineering Inc

[ktmkirk]

Thanks Everyone for all of the replies I'll try to get time to check the adjustment in the next week and hopefully that is it, If not I may have to watch where I go until I can afford to have the repairs done. ..Kirk


[quote="lindenengineering"]Yes , that repair was expensive since no-one had a used t/case available so we had to make one from parts we had on the shelf.

That activity was more than three years ago, then the Hi gear pinion was $850, the Lo was $1230, the rest was chump change at about a $2500 for a reclaimed case and sundries like a mainshaft and drive gear.

Although important the cost is outlined to illustrated the need to take care of this sub assy which is (or at least can be) extremely expensive to fix if it grenades on the highway. (towing for Al's truck was $1600)

Just a footnote, for those of you who do DIY a T/case repair be carefull on dismantling and reassembly of the case halves. One RMP member "individual who shalt remain nameless" broke his case halves when trying to force them together with the fixing studs.
Another tip is to load the case to assimulate the "crush condition" it experiences being loaded into the drive line arrangement.
Experiments have shown that a considerable mainshaft preload can exist after insertion within the drive arrangement to cause premature failure of mainshaft bearings or even seizure causing parent case journal wear!
Yes we do have a fix to recover that by the way, and it doesn't involve welding. That activity (highly skilled alum stitch welding) incidently usually results in case distortion dictating a line boring/sleeving adventure. In either case it all adds up to money out of your pocket or the Anglo American perpetuation of "revolving debt" (credit cards).
Take care
Dennis
Linden Engineering Inc[/quote]