Cab mounts

[WPVT]

I'm replacing the cab mounts on my 1954 C-1-B6 truck.  The existing stock mounts front and rear are very close to the image attached except that the lower part is 1 3/8" thick and the upper part is 1 1/8" thick. Both parts are 2 1/2" in diameter. I've seen some offered for sale that look similar, but not these dimensions. The 2 1/2" is fairly important, and the 1 1/8" dimension is also. The 1 3/8" dimension, the thickness of the lower part, could vary if need be. Does anyone know of a source that offers the mounts to these dimensions or close ? (The left front mount is different, but that doesn't concern me at this point.)

 

The second part of my question involves the steel part labelled as a bushing. This is a tee shaped assembly consisting of a tubular spacer and a large washer. This was inserted from above, before the cab was installed. Obviously, this makes replacement a little difficult, unless you raise the cab up at least 2". I'd rather not do that, so I may end up separating the tubular spacer from the washer using a small Dremel cut-off saw to enable removal. I did this on my motor mounts, as they were assembled the same way. Has anyone run into this problem and did you come up with a solution ? 

 

 

Edited November 19, 2020 by WPVT

[JBNeal]

To replace the cab mounts, I removed the bolt and lower rubber, lifted the cab enough to get the weight off of the upper washer, then grasped the spacer tube with some needle nosed vise grips to wiggle that tube out of the washer, as I assumed they were pressed together.  Once it broke loose, I worked that tube out of the upper spacer.  I used a trolley jack on the running boards, with a 1" thick plywood scrap under the jack and a 2x6 strategically placed under the cab, and lifted the cab just enough to extract the old rubber...new rubber was taller so I had to jack the cab up a little more to set it in its new location.

[WPVT]

14 minutes ago, JBNeal said:

To replace the cab mounts, I removed the bolt and lower rubber, lifted the cab enough to get the weight off of the upper washer, then grasped the spacer tube with some needle nosed vise grips to wiggle that tube out of the washer, as I assumed they were pressed together.  Once it broke loose, I worked that tube out of the upper spacer.  I used a trolley jack on the running boards, with a 1" thick plywood scrap under the jack and a 2x6 strategically placed under the cab, and lifted the cab just enough to extract the old rubber...new rubber was taller so I had to jack the cab up a little more to set it in its new location.

Thanks. I follow your procedure. Good news if the spacer is just pressed into the washer....I thought it might be a weld. If it's pressed in, I may be able to separate it with a punch from above. I hadn't considered that possibility. Putting a jack on the running board is also a good idea. If I jack off the floor, I may just lift the whole truck. I've located some polyurethane mounts that are the size I need.  The thickness on upper one is critical if I'm not going to change the cab height.

 

Thanks again.

[ggdad1951]

on my rebuild the rubber and metal bits just came apart with no issues and no issues putting back together either.  As JB said lifting the cab just enough will go a long way in reducing what you have to dismantle.

[Lingle]

I ordered a new set of cab mounts from DCM, and unfortunately the washer and tube are welded together, so if you can reuse your old metal parts, that may be useful.  I had not looked closely at the mounting strategy so been installing incorrectly, but my project is far from driving, so that is ok.  Downside I see to the DCM for the 48-53 B series is that they have 4 thick and 4 thin rubber parts.  May be different for the C series, although the diagrams are identical to what you show above.  Just some thoughts on if you buy a new set of cab mounts, the washer and bushing may not be separate parts. 

Edited November 20, 2020 by Lingle
changed 52 to 53 as year range was incorrect

[ggdad1951]

The top washer and bushing should be one welded piece.

[kencombs]

16 hours ago, WPVT said:

Thanks. I follow your procedure. Good news if the spacer is just pressed into the washer....I thought it might be a weld. If it's pressed in, I may be able to separate it with a punch from above. I hadn't considered that possibility. Putting a jack on the running board is also a good idea. If I jack off the floor, I may just lift the whole truck. I've located some polyurethane mounts that are the size I need.  The thickness on upper one is critical if I'm not going to change the cab height.

 

Thanks again.

 You may want to examine the polyurethane mount carefully.  The rubber mounts are there to isolate the cab from running gear noises.  Many of the poly items on the market are way to hard to do that well. 

 

And, some seem to be compounded with short lived plastic.  I had a set of poly band saw tires just fall apart in less than 2 years.  The poly tires on my tool box casters did the same in about 3 years.  And neither of those were ever exposed to sun or weather.  The Poly rear suspension bumpers on my old mini-van fell apart in 9 years.  

 

In short, if a plastic  came from the other side of the Pacific, I'd pass.

[WPVT]

I was able to remove the steel spacers by using a punch, from above, to separate the spacer from the washer. The spacer was manufactured with a small shoulder where it was pressed into the washer and swaged.  Once they were removed, I was able to jack up the cab enough to slide out the upper rubber bushing. Now it remains to find or fashion replacements. I am attaching a photo of the components. I am guessing that the the upper and lower bushings were originally identical, but the weight of the cab has distorted the upper.

I think I'll be able to reuse the steel spacer by reversing the process I used to remove it. It prevents the bolt from being over tightened, which would negate the vibration dampening qualities of the rubber. 

I'm guessing that the rubber was a medium soft durometer when it was new, judging from the swelling that the cab weight induced in the upper bushing and the indentations from the large washers.  At present, I've found no supplier that sells the bushings this size. Most are smaller diameter and thinner.     

[Tooljunkie]

I got mine from vic’s. Right up there in the vendor’s thread. 

[WPVT]

1 hour ago, Tooljunkie said:

I got mine from vic’s. Right up there in the vendor’s thread. 

Thanks. I contacted Vic to ask for dimensions to see if they would work.

 He's a great guy to do business with.

 

[Tooljunkie]

I have made a couple purchases from vic. Nice guy. 

[CO54]

On 11/20/2020 at 5:47 PM, WPVT said:

I was able to remove the steel spacers by using a punch, from above, to separate the spacer from the washer. The spacer was manufactured with a small shoulder where it was pressed into the washer and swaged.  Once they were removed, I was able to jack up the cab enough to slide out the upper rubber bushing. Now it remains to find or fashion replacements. I am attaching a photo of the components. I am guessing that the the upper and lower bushings were originally identical, but the weight of the cab has distorted the upper.

I think I'll be able to reuse the steel spacer by reversing the process I used to remove it. It prevents the bolt from being over tightened, which would negate the vibration dampening qualities of the rubber. 

I'm guessing that the rubber was a medium soft durometer when it was new, judging from the swelling that the cab weight induced in the upper bushing and the indentations from the large washers.  At present, I've found no supplier that sells the bushings this size. Most are smaller diameter and thinner.     

Those look very close to my '54 C-1-C.  Only difference was mine were all washer/spacer/washer.  Came apart as 3 pieces.  You are correct on the Left Front being an odd ball too. Same size upper bushing, no sleeve and larger/shorter diameter bolt.

[WPVT]

16 hours ago, CO54 said:

Those look very close to my '54 C-1-C.  Only difference was mine were all washer/spacer/washer.  Came apart as 3 pieces.  You are correct on the Left Front being an odd ball too. Same size upper bushing, no sleeve and larger/shorter diameter bolt.

Sounds just like mine. Turns out Vic's Dodger Garage has the exact match rubber.  

 

Washer/spacer/washer sounds like a more practical design when it comes to replacement. I'll reassemble mine that way. 

 

The motor mounts look the same, but the spacer design length was intended to provide with a bit of clearance...not compressing the rubber. That way they do their job a lot better. Compressing the rubber just serves to transmit the engine vibration to the frame.

 

I'm not sure the cab mounts were intended to be left with clearance, though. They take a lot more stress in both directions. The spacer length on my cab mounts seems designed to allow the bolts to be tightened pretty firmly. Even after being squashed for all these years, the bolts were still tight on the spacers, so they must have been pretty tight originally. 

[WPVT]

I installed the new mounts today. The spacer/washer assemblies were kept separated, the washer installed above, and the tubular spacer pushed up through the rubber from below to mate with the washer. What I ended up with was exactly what was there originally. Although the old mounts appeared to be in good shape, and weren't overly compressed, the new mounts made a big difference in the way the truck sounds and feels going down the road. So if somebody is wondering whether changing out the old mounts is worth it....it definitely is. 

[rlg0613]

I know this is an older post, but hoping for a response. The instructions in my manual mentions a double insulator on the driver side. The picture from my driver side shows no lower insulator but only one upper insulator. Do you normally stack two insulators, one on top of the other for the driver's side? My truck has always had a sag on the front left side and I'm thinking this is the reason. Sorry for the poor image, but it was tough to even get this one. Thanks for any help you can provide. BTW it's a 1955 C3B.

Edited February 15, 2023 by rlg0613

[WPVT]

Here's a very late response. The thing to keep in mind with these is the basic principle, which was not obvious. The purpose of the tubular spacer is to prevent the bolt from tightening down on the rubber cushions. The cab sits on the upper cushion by its weight, not by the bolt being tight. If you tighten the bolt onto the rubber cushion, you are back to transmitting the frame vibrations to the cab. The cab needs to float.

 

In answer to your question, if you read the installation closely, you'll see that the height is adjusted with spacer washers if needed, not by adding cushions. As I recall, the driver's side mount has a cushion above and below the bracket, the idea being that the engine torque will work against the weight of the cab, and lift the cab up as well as the force of gravity pushing it down. Again, don't neglect the tubular spacer and its purpose. If you use the bolt to tighten the cab to the frame ( even if there's rubber in between), you lose the vibration insulating.

 

Imagine the mounts this way. The cab just sits on the frame by gravity. The frame and engine vibrate, but the cab just sits loosely on top of a rubber cushion and receives little of that vibration. The bolts serve to keep the cab from lifting off the chassis when you hit a bump or go around a corner.  Squeeze the rubber cushions with the bolts and none of that works.

[rlg0613]

Thanks for the response. As it turns out washers and spacers did the trick. The cab sits nice and level.