Sprag Transfer Case

[3rdmdqm]

1968 Deuce with Sprag transfer case. Had to take the front drive shaft out due to issues. Was thinking maybe it was an adjustment issue, but given what I am about to describe was hoping someone with intimate familiarity could provide some input. While driving occassionally Deuce would start wobbling in front end, then after a sharp turn wobbling would go away. One time it felt like the right front tire was flat (due to wobbling), then made left turn and everything was fine. Sometimes while driving would pull sharply to one side. Short time later after driving for a while, went to pull into a parking garage, wobbling, made left turn and heard very loud boom, like a detonation and then everything was fine. Removed front drive shaft and have never had another issue. Problems are definitely with sprag transfer case. Could be an adjustment issue, as most issues developed if truck drifted backwards a few inches/feet prior to pulling forward. My question is this: given the loud detonation sound at last incident, what would cause that? Is the system still salvageable with adjustment or should I look for metal shavings in the case from broken parts if I drain the transfer case? Right now everything runs/works fine without the front drive shaft, I'm just looking for input to get it back to proper stock/original operating condition. Yes, I know about how changing over to air transfer is better, I'm looking for input on the sprag system in particular. Thanks in advance.

 

[KsM715]

Personally, I would atleast drain it and see what parts come out. Given what you described there are probably pieces floating around in there that sooner or later is either going to lock up the t-case or damage the gears. No matter what, something is wrong and need to be looked at.

 

[212sparky]

Remember NEVER drift backwards while in a forward gear. the loud bang was the sprag engaging, youe case may be to far gone.

 

[gimpyrobb]

Could be a ring and pinion issue in the axle too. I say put the DS back in and pull the spline caps. Are you sure the bearings aren't the issue? Time to spend a day taking things apart and inspecting.

 

[welldigger]

From your description I would start with your steer axle like gimpy said. I almost wonder if the bang you heard was your spider gears or your pinion hand grenading. Also with the wobble you describe I strongly suggest you check your front wheel bearings and tie rods. Actually, I would jack the truck up and pull that whole front axle apart. Pm me if you need parts. I have access to everything rockwell in the 2.5 ton.

 

[3rdmdqm]

Thanks for the replies. I guess I will be pulling things apart. Since drive shaft was removed, there have been no further issues, no wobbling, no pulling etc. Even after the loud bang, the truck drove fine. Was very sporadic. However after the bang and then a few days later after driving on a hill when it began the jerking/wobbling until the turn when it went back to normal I removed the drive shaft and have had no further issues. I'll start checking everything, thanks.

 

[3rdmdqm]

Curious about the loud bang though. What would cause that noise? Steel twisting/snapping in case?

 

[RAYZER]

I have a sprag tc also, i have experienced the loud bang on occasions too, its caused by the sprag being locked in,say foward when your backing up, this puts everything in a big bind,and Bang! The sprag jumps out.
I have an air shift tc that i am going to install soon in place of the sprag.
It is rumored that the sprag setup is bad design,when it's working, it only works in 1st or reverse, not good when you have to encounter a mud hole in low 2nd, i don't think lock out hubs can effectively be used with the sprag setup either.

 

[73m819]

Lock out hubs are a no-no with a sprag, the sparg will think the rears are spining and then "drive" the front third member, the sprag shifts in to reverse or forward (any gear), it goes into reverse or comes out of reverse into foward, there is NO nutural like the 5t when the air is shut off.

As a side note, dropping the front driveshaft will also make the sprag think the rears are spinning and engage though only driving the front output drive flange

 

[3rdmdqm]

Since I removed the front drive shaft, I don't think the Sprag is engaged at all. Handles much better and seems to get better gas mileage. I am curious as to how this system actually works. Is it similar to a limited positrack system? When it senses the rears spinning faster than the front, does it tighten up on the front axle shafts (like a friction system like an expandable baton) and then loosen back up when they are the same speed?

 

[212sparky]

It is similar to an over running clutch. As long as they spin the same speed all is well, once the rears speed up it locks in the front drive.

 

[pegasus55]

The loud bang is the energy bound up in the driveline suddenly releasing when the sprag disengages. I have a sprag system in my deuce and have had this (loud bang) happen if I let it roll back while the tranny is in a forward gear and fail to release it before continuing down the road. Since that time (it gets your attention) I have been conscious of this phenomenon and am careful not to repeat it. If your sprag is intermittently engaging while going down the road has definitely got my attention...this sounds scary.
Relating to my experiences in the Haspin mud, my sprag will engage as expected as soon as the rears begin slipping...regardless of what gear I'm in.

 

[JasonS]

It is rumored that the sprag setup is bad design,when it's working, it only works in 1st or reverse, not good when you have to encounter a mud hole in low 2nd, i don't think lock out hubs can effectively be used with the sprag setup either.

The sprag transfer case works in all gears.

 

[JasonS]

Lock out hubs are a no-no with a sprag, the sparg will think the rears are spining and then "drive" the front third member,As a side note, dropping the front driveshaft will also make the sprag think the rears are spinning and engage though only driving the front output drive flange

What is the problerm with this? Someone posted here recently that they installed lockouts with a sprag xfercase and it worked fine.

 

[KsM715]

It will work fine but wont gain you anything but maybe the steering may be a little easier. With the freewheeling hubs the t-case will think the fronts are not turning and inturn engage and spin the driveshaft, spinning the diff. and basically gaining you nothing in the end.

 

[JasonS]

It will work fine but wont gain you anything but maybe the steering may be a little easier. With the freewheeling hubs the t-case will think the fronts are not turning and inturn engage and spin the driveshaft, spinning the diff. and basically gaining you nothing in the end.

It will prevent the driveline windup. I agree you'd be money ahead to get the air shift xfercase, though.

 

[jamawieb]

Memphis Equipment sells a kit that makes the sprag transfer case engage when you want it to, just like the air engaged transfer case. I bought a duece a few months back that has it installed and it works well. They put an engagment lever on the floor next to the swifter, so you can engage and disengage the transfer case.

 

[212sparky]

Have some pictures of this?

 

[73m819]

Memphis Equipment sells a kit that makes the sprag transfer case engage when you want it to, just like the air engaged transfer case. I bought a duece a few months back that has it installed and it works well. They put an engagment lever on the floor next to the swifter, so you can engage and disengage the transfer case.

This WAS the "REB" kit, no longer made, it was MORE then a engagement lever, it did away with the sprag ( about 8% over running clutchs) by having a 1 to 1 sliding clutch installed instead

 

[cx65083]

Do they have anything like the REB kit for the 5 ton transfer case?