D25 early vs late knuckles

Can anyone tell me the bearing cap surface to bearing cap surface measurements of the early Dana 25 knuckles vs the later knuckles? I'm working on my front axle and which was had a lot of work done in the past (not stock) and I want to be sure which style knuckle I have so I can shim the king pins accordingly.

The knuckle I have is 6 3/8 inches accross.

Thanks for your time.
-Dean

 

I went out and eyeballed a measurement best I could on my model 25 front axle and 6 3/8 is what it looks to be. does it look like someone has modified the bearing cap surfaces?

 

I'm in the process of setting the preload but I read somewhere that early d25 knuckles need shims (.058 thick) between the bottom king pin and the knuckle where the later 25s and 27s only used shims on the top. I want to be sure I didn't end up with an early 25 knuckle on my axle which would require shims on the bottom.

-Dean

 

I dont have any historical knowledge regarding that manufacturing change but the model 25 in my 55 cj only has shims on the top.

 

I am inclined to agree, I did the knuckle seal on the drivers side some time back and the shims were on the top, Last night I started to do the knuckle seal on the passenger side and the shims are on the bottom

No surprise there, This poor old cj had a hard and neglected life. Maybe thats why the jeep leans a little......Its .050 higher on the passenger side

Its been that way for who knows how long, Apparently with no detrimental side effects, The passenger side axle was replaced with the Cardan joint type at some point in time, The drivers side still has the Bendix joint type axle. Its still a mystery because the axle can be replaced without removing the knuckle.

I am curious though and plan on trying to take some measurements to see if there is any real difference that would matter, I cant see how there could be.

I plan on putting both shim packs on top as my FSM shows.

 

I dont have a clue about any real differences dimensionally but I will be working on it ( my model 25 ) some more today and will make it a point to take some measurements while I have clean parts in my hands. Then maybe if/when someone has a model 27 down notes can be compared.

 

To the best of my knowledge the only difference between the dana 25 and dana 27 knuckles is the casting. The 27 knuckle is heavier and has some more material around the steering arm to strengthen it up. As far as the shims go, I measured a dana 25 and 27 and the machined area for the shims was relatively the same.

 

Maybe it was a year thing then. They might have started casting all the knuckles heavier after a certain point in time and the ones I had were from a very early model.

 

I'm using knuckles from a '70 D27 on a '48 D25 axle. The only difference I see is the 27 knuckle is beefier.
I compared king pin caps when I put it together and found some to have a slightly talled boss so I put those on the bottom without any shims. Actually the D/S knuckle didn't get any shims top or bottom in order to get the proper pre-load. Mabey this will help some.
Tommy

 

One side apart and cleaned up , From reading everyones posts it looks like any real difference is in the casting of the knuckle and not a dimensional issue. Just for giggles the diameter of the spherical end of the axle on my model 25 is 4.960" ( after resurfacing ) and the distance between the bearing race seats is 3 15/16".

There were no shims on the passenger side, What I thought was a shim was actually a small step or ridge left over from machining on the bearing cap..........Looks like the jeep lean is from to many fig newtons and not a shim on the bottom

I did dig out an old 1964 Ford Truck FSM and it does show shims being used/split on top and bottom on a Spicer Model 2559 front axle but does not say why. It also shows using an Inch Pound Torque Wrench on the rear inside bearing cap bolt ( rather than a pull gauge in the tie rod hole ) and adjusting bearing preload to 50-70 inch pounds. If my math is correct that translates to 4.16 to 5.83 pounds on the torque wrench handle using that method.

I have wondered about the 12 to 16 pounds in the Jeep FSM ever since I tore into the drivers side last year, It did have shims on the top but was no where near 12 pounds let alone 16, It was close to 6 pounds using the pull gauge method, There was no wear in any of the bearings or bearing caps and no play with the weight of the vehicle on it so I put it back as was. Same story for passenger side, pull gauge shows 3 pounds 7 ounces, there are no signs of wear on the bearing, race or shoulders of the bearing caps and I cannot get any play out of it with the weight of the vehicle on the bottom bearing cap and a lever bolted to the face of the knuckle.................Anyone else ever wondered about the 12-16 pound preload?

 

I would make it at least 12lbs.
Play is not so much an issue as preload on all of it. I would make it like the service manual says, other wise you will have steering problems of one kind or another. Besides that you can't possibly put the load on the front end trying to move it by hand that the road and tire leverage at speed can.

 

There could be two reasons for the preload that I can think of.

First, the kingpin bearings themselves may need to operate with a specific preload. The preload then would be related to the static axial force on the bearings. The axial force would be spec'd to prevent any radial movement under normal load - ie keeping the bearing seated in the race so that all the rollers are in contact with the race, plus some room for a lubricating film. Too little preload and the rollers come out of contact with the races, causing uneven wear.

The preload could also be adding some lateral damping to the suspension. If the front suspension has a tendency to resonate at a specific frequency, adding some additional frictional load will dampen any resonant oscillations. Note the suspension may only be resonate under specific road conditions, speed, tire size (mass), tire balance, etc etc. Looser knuckles may allow some shakes and shimmies that migh otherwise be dampened out.

JMO - set them to spec.