I just bought an M38A1

Oldsalt · Post by **Oldsalt** » Tue Jun 14, 2011 8:54 pm

The primary cause of Death wobble is that the King pin bearings (the hinges that allow the front wheels to swing side to side) are worn and loose. The front wheels are supposed to be rather stiff to move side to side. The condition of the rest of the steering mechanism can control the shimmy if it is in good condition but only so far. Lots of jeeps have a shimmy damper (a shock absorber mounted on the steering arms) to create some artificial stiffness and stop the shimmy, but they are not really fixing the real problem. Rebuild the king pin bearings in the steering knuckles and the problem will be gone.

There is an adjusting screw on the steering sector. It is on the side of the sector gear case opposite the output shaft. Loosen the nut and turn the inner shaft with a screw driver. But if there is a lot of slop in the sector it probably needs to be rebuilt.

Deadguy · Post by **Deadguy** » Tue Jun 14, 2011 10:37 pm

So, should I get kingpin bearings and the cups? Should I get them for both axles?

Post by **wesk** » Tue Jun 14, 2011 10:48 pm

The steering you describe is really in a sorry state. The prior owner is clearly blowing smoke up your canal. I wouldn't waste any more dimes in your phone to call him.

1-Clutch- Only an idiot would install a new clutch and not adjust it. It only requires 5 minutes while you are under the jeep.

2-Steering - Only an idiot would sell you a jeep with worn out steering ball joints and king pin bearings and tell you to adjust the pre-load screw on the steering gear box.

3- Fuel line - Only an idiot would install the fuel lines on an M38A1 with an F134 engine between the block and the exhaust manifold.

Ok, with that made clear so that now you should have a very good idea what kind of person the seller was lets see if we can get you on the road.

Clutch, adjust pedal for 1" free play.

Here you can see the clutch cross shaft and the adjustment linkage on the right.

Steering - Jack the front of the jeep off the floor using the front axle housing to lift with. Secure the steering wheel so it cannot move. grasp a front tire at the front and rear edge and try to move it left and right while watching each of the tie rods, the drag link, the steering bellcrank and the pitman arm for loose movement. Write down each part that is sloppy. Now grasp the tire at the top and bottom and try to move each in and out. A very slight feeling of movement at the axle for the wheel bearing is ok. Movement of the wheel on the axle that can be seen means the wheel bearings need to be adjusted. Noticable movement of the steering knuckle ball will indicate worn king pins (steering pivot bearings). Now you have a fix it list to work on.

Fuel Line - The fuel line runs from the fuel tank to the right frame rail then up to the front crossmember and then over to the left frame rail. There it has a flex hose connecting it to the fuel pump. From the fuel pump the fuel feed line goes around the front of the block by the water pump and back to the carb base then up and around to the carb inlet fitting. It was never meant to be anywhere near the exhaust manifold.

Here you can see the fuel supply line (hose) entering the fuel pump upper fuel section and the steel tube leaving the upper fuel section going immediately around the front of the block.

skyjeep50 · Post by **skyjeep50** » Wed Jun 15, 2011 8:24 am

The adjusting screw on the steering box is there to provide a slight resistance when the sector shaft is in the middle of its travel along the worm gear. Which is a slight resistance when the jeeps front wheels are straight ahead and everything is centered. The screw tightens the sector shaft against the worm gear which is slightly higher in the middle than at each end. Overtighten this screw and you will just wear down the sector shaft and/or worm gear. It does nothing to eliminate death wobble. As mentioned before, the king pin bearings provide the stiffness to control wobble. New seals on the steering knuckles add even more resistance. In fact, once everything is tighted to spec it almost seems there is too much resistance but that is what it takes to control wobble. One of the M38A1's Achilles' Heels is that steering gear components such as the sector shaft and worm are not manufactured as replacement parts (you can get replacement sector shafts for the early CJs). New seals and bushings are available. You can buy NOS replacement steering gears as a whole part, kind of expensive, but that is about the only way to go unless you find a take-out part in good condition. My M38A1 has a steering damper to correct a rather loose action - not the best solution but it works until I get around to a permanent solution.

Deadguy · Post by **Deadguy** » Wed Jun 15, 2011 10:00 pm

Do I have to pull apart the axles to replace the Kingpin bearings?

Post by **wesk** » Wed Jun 15, 2011 10:43 pm

Do I have to pull apart the axles to replace the Kingpin bearings?

Here's where I must say it's time to read your manual. It will be very obvious to you in about 3 or 4 minutes of reading that some dis-assembly is required.

I haven't seen a complete NOS M38A1 steering gear box in a lot of years. I have seen a lot of Government Rebuilds fresh in the box. Midwest Military sells them right now.

The A1 sector shafts and worms are hard to find but they can still be found. The worn tits on the sector are the real problem and they can be repaired.

The "Steering Damper" the aftermarket cure all for what ails your jeep's sloppy steering linkage is nothing more than a band aid and the only part of the front end it really dampens excess motion on is the tie rod linkages which by the way can be replaced with new tie rod ends all the way across for less then the cost of the "Steering Damper"! The proverbial Death Wobble will still occur with the steering stabilizer installed because the wobble is caused by the worn king pin bearings (Pivot Bearings) allowing the wheels to move in more directions than just left and right.

1 - Shimmy is a right and left oscillation of the wheels caused by worn tie rod ends, worn steering bell crank bearings, worn drag link parts and worn steering gear internals. A terrible shimmy is caused by dangerously worn parts.

2 - Wheel wobble is caused by loose wheel bearings and/or worn King Pin Bearings (Pivot Bearings). A terrible wobble is caused by dangerously worn parts.

3 - Wheel hop is caused by severe imbalance in the tire/wheel combination.

The proverbial death wobble is usually both 1 & 2 or 2 & 3 above combined.

Deadguy · Post by **Deadguy** » Wed Jun 15, 2011 11:44 pm

Yeah, I got a rebuilt one from Midwest Military. I got new tie rod ends, a bellcrank rebuilt kit, a new pitman arm, and new shocks. I know I have to jack up the truck and pull off that front wheel and hub, I was just wondering how far in I will need to go. Do I have to pull the axle shaft? Should I replace the wheel bearing while I'm at it?
And, will I need to replace the Kingpin bearings on the back axle as well?

MODIFIED · Post by **MODIFIED** » Thu Jun 16, 2011 5:25 am

Deadguy, the manuals have an excellent and thorough trouble-shooting procedure.

skyjeep50 · Post by **skyjeep50** » Thu Jun 16, 2011 7:21 am

Once you take apart the front hubs, steering knuckles/king pin bearings/seals, axle bearings, the axle shafts themselves are just sitting there and slip out with no problem. There are no king pin bearings on the rear axle, they are installed on top and bottom of the steering knuckles to allow the wheels to pivot - the axle shaft itself has a universal joint. You can inspect bearings once they are out and cleaned to see if they need to be replaced but most likely, if there is a lot of looseness, they will need some attention. You can also check out brake pads, cylinders and the flexible brake lines at the same time - its all going to be taken apart. Be prepared for lots of dirt and grease, cleaning up axles on jeeps that haven't had routine maintenance in a while is a real grubby job - but fun if you like getting grubby! And your jeep will thank you.

Deadguy · Post by **Deadguy** » Thu Jun 16, 2011 11:12 am

Thanks everyone-never done an axle job before. The hubs and breaks are the farthest I've gotten!

Bretto · Post by **Bretto** » Thu Jun 16, 2011 1:04 pm

This got me thru it.

http://www.vernco.com/FrontAxle/

Did you ever get some pics of the wheels yet?

Beacher425 · Post by **Beacher425** » Thu Jun 16, 2011 1:05 pm

One other source of sometimes more detailed step by step instructions can be found in the Civy maintainance manual for the Universal Jeep.

Deadguy · Post by **Deadguy** » Thu Jun 16, 2011 7:07 pm

Yeah dude, I need your email to send them!