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MCI 102-C3 coach to RV - Chassis/Suspension

Some extras for future reference:
jd8420 has been of excellent assistance in this matter, so I credit him. I’ve been stealing shots from spinneybent and mx_racer_36 on their threads.

The 4000 narrow and wide planetary steer, rigid and ISAS units using Haldex calipers all use the same caliper part number 757011020E. Therefore, the brake chambers are interchangeable. The only drawback would be clearance between the chamber and axle housing when installing an 18/24 spring chamber on a steer axle. From what I can tell, the caliper brackets are held onto the spindles by 16 Allen head bolts in a concentric circle, providing clocking in 22.5 degree increments.

All of the 4000 series steer axles that I’ve found in the last week have the same chamber with two air inlets at the top and a single port/plug/bolt in the center that I can only assume is a caging bolt, at this time. The chambers are “type 24”, but searching that name only brings up a single-port chamber that appears to only be a service brake. The same single-port chamber illustrated in every AxleTech 4000 series manual.

Pulling up a type 24 chamber will provide mounting specs. 5/8-11 studs spaced at 4.75” between centers. This would also apply to the 18/24 spring brake chamber. Looks to me like chambers are built with standard specs very much like SAE flange mounts. The 18/24 chambers appear to use the same “inboard” service brake chamber section that the 24 chambers use, hence the shared numerical designation. Maybe one can swap chamber shells to obtain various functions and forces? I need some air brake design 101 before making any further assumptions in that regard.
 
bdkw1 said,

Do the steer axles have brakes that default to on with no pressure? In my very limited experience only the rears need caging bolts if you don't have air.
 
bdkw1 said:
Do the steer axles have brakes that default to on with no pressure? In my very limited experience only the rears need caging bolts if you don't have air.​
I think we’re all about to find out. I’m snagging a chamber from jd4820 to tear down (carefully while assuming there is intense spring force inside it). Hopefully Leo from AxleTech has some documentation on the exact chamber that’s on these steer axles. If not, I’ll lay it all out right here. Load of sample pictures coming shortly.
 
Yanked these from Pirate and craigslist. All 4000 steers including the newer ISAS have the same chamber. Two air inlets.

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Two chambers currently listed on eBay. Same part number. Look identical to the chambers on the axles. Two air inlets. Empty center port thingy on the ugly one. Plug/bolt in the pretty one. I’ve ran every name and number associated with these and gone through every site containing them that I could find. Nothing.

443.jpg
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https://www.axletech.com/at-admin/re...ls/90138gb.pdf

Skim through this. Every manual displays the same brake system. Single-port service brake on the steer axles. Every now and then, there’s a quick safety instruction to chamber the spring brake if your axle is equipped, but the illustration looks similar to the rear spring brake chamber. jd8420 and I have been discussing this for a couple days and still don’t know what the second air inlet is for. We both agree that it would seem to be for releasing a spring brake. All I can think of otherwise is some kind of two-stage chamber. Thoughts?
 
[486] said,

I'd bet on a vent line to be routed above the waterline

doesn't look like there'd be two diaphragms, much less room for a spring in there
 
[486 said:
I'd bet on a vent line to be routed above the waterline

doesn't look like there'd be two diaphragms, much less room for a spring in there​
Thought about that. Port seems rather large for a vent and I haven’t seen evidence of a vent on any other chamber or any venting described in the manuals. Maybe this was a special chamber design requested by AxleTech or the outfit using the MRAP vehicles and installed later?
 
This is the single-port/single-diaphragm type 24. Small vent hole in the chamber shell. Anxious to open one up to see why there’s two or even three ports. I agree that they’re too small for a park spring. That’s what had me so curious about the configuration because all the spring brake chambers are something like three times the size.

2917174-0fe3a1e2b9df24840fb33abb390a0b68.jpg
 
bdkw1 said,

The ones with the rubber center plug need caging bolts to release. The one with the screw i bolt does not. Fronts should have the screw in bolt style.
 
bdkw1 said:
The ones with the rubber center plug need caging bolts to release. The one with the screw i bolt does not. Fronts should have the screw in bolt style.​
Noted. I wouldn’t think there’d ever be a spring brake on a front axle since they lock by default when there’s air loss. Curious if these axles ever got used for rear steer coupled with a rigid center axle and had something more than a service brake. I should be opening one up in the next week or two.
 
A few from jd8420. Confirmation that this is not a spring brake and that the inside port is indeed most likely a vent that can be routed as a snorkel. He’s still sending it to me to tinker on. I’d say you could also actuate the plunger with the center port and possibly run a bolt in to push the plunger and lock the brakes for servicing if you don’t have air.

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bdkw1 said:
You should check out the 6X6 my buddy Smitty just finished up.

https://www.instagram.com/p/BtMZKS9gBIy/

There are plenty of pics on his IG.​
Yes! See, I’m not that crazy after all lol. We didn’t know the conversions were such a hot trend until after we almost bought a Bluebird in Tucson. Now I’m seeing a bunch of skoolie converters and big RVers downsizing merely because they can’t get their rig into the secluded locations that they want to stay in. Have your cake and eat it, too, I say.
 
bdkw1 said:
That's why I'm building a step-van. It will only be 4X, but the size is right.​
I hear ya. We wanted a comfy rig for our family of four. The couples make van life look easy. Add kids and my load of fabrication tools...
 
02rexwi said,
JNHEscher said:
Some extras for future reference:
jd8420 has been of excellent assistance in this matter, so I credit him. I’ve been stealing shots from spinneybent and mx_racer_36 on their threads.

The 4000 narrow and wide planetary steer, rigid and ISAS units using Haldex calipers all use the same caliper part number 757011020E. Therefore, the brake chambers are interchangeable. The only drawback would be clearance between the chamber and axle housing when installing an 18/24 spring chamber on a steer axle. From what I can tell, the caliper brackets are held onto the spindles by 16 Allen head bolts in a concentric circle, providing clocking in 22.5 degree increments.

All of the 4000 series steer axles that I’ve found in the last week have the same chamber with two air inlets at the top and a single port/plug/bolt in the center that I can only assume is a caging bolt, at this time. The chambers are “type 24”, but searching that name only brings up a single-port chamber that appears to only be a service brake. The same single-port chamber illustrated in every AxleTech 4000 series manual.

Pulling up a type 24 chamber will provide mounting specs. 5/8-11 studs spaced at 4.75” between centers. This would also apply to the 18/24 spring brake chamber. Looks to me like chambers are built with standard specs very much like SAE flange mounts. The 18/24 chambers appear to use the same “inboard” service brake chamber section that the 24 chambers use, hence the shared numerical designation. Maybe one can swap chamber shells to obtain various functions and forces? I need some air brake design 101 before making any further assumptions in that regard.​
Send me a PM if you need any information on the Axletech axles.

I just finished reading through your posts. Good work!

I can confirm, the brake chambers on the steering axles and the rigid axles are interchangeable. The common 4000 series axles that are on the market should all have the same physical mounting dimensions for the brake chambers. There are many different sizes of chambers available to tune the brake torque to your application. Type 24= 24 square inches of surface area in the diaphragm. The parking brake chambers are available in many different sizes as well. The main issue you'll have mounting a parking chamber onto a steer axle is going to be the limit of steering angle with that large chamber.

The service chambers sometimes have 2 or 3 ports. Typically there is one port for a snorkel line (so no water gets inside the brake) typically needed for water fording applications. The other 2 ports are optional inlets for the service actuation of the brake. The other picture that was posted up of a 4000 series axle showed a hose connected to the steering knuckle. That was a vent line for the oil in the wheel end. Typically that's only used when the axle is equipped with central tire inflation (in case there is a leak).
 
02rexwi said:
Send me a PM if you need any information on the Axletech axles.

I just finished reading through your posts. Good work!

I can confirm, the brake chambers on the steering axles and the rigid axles are interchangeable. The common 4000 series axles that are on the market should all have the same physical mounting dimensions for the brake chambers. There are many different sizes of chambers available to tune the brake torque to your application. Type 24= 24 square inches of surface area in the diaphragm. The parking brake chambers are available in many different sizes as well. The main issue you'll have mounting a parking chamber onto a steer axle is going to be the limit of steering angle with that large chamber.

The service chambers sometimes have 2 or 3 ports. Typically there is one port for a snorkel line (so no water gets inside the brake) typically needed for water fording applications. The other 2 ports are optional inlets for the service actuation of the brake. The other picture that was posted up of a 4000 series axle showed a hose connected to the steering knuckle. That was a vent line for the oil in the wheel end. Typically that's only used when the axle is equipped with central tire inflation (in case there is a leak).​
Highly appreciated, sir. I'll have more questions once we approach the time to purchase axles. Quite the situation we're dealing with over the house at the moment.

JD8420 and I were conversing about axle series and parts interchange for a while. I eventually found the info I was after in regards to the brake calipers and chambers. Figured I would have to wait until we bought a front/rear pair to swap park chambers on a steer axle to measure clearances.

JD also pointed me towards a 5000 series ISAS on eBay and I still have contact info for a seller with 4000 series ISAS units. I think I actually would consider the independent units over straight axles if the price were right. Keeping my eyes open.
 
02rexwi said,
JNHEscher said:
Highly appreciated, sir. I'll have more questions once we approach the time to purchase axles. Quite the situation we're dealing with over the house at the moment.

JD8420 and I were conversing about axle series and parts interchange for a while. I eventually found the info I was after in regards to the brake calipers and chambers. Figured I would have to wait until we bought a front/rear pair to swap park chambers on a steer axle to measure clearances.

JD also pointed me towards a 5000 series ISAS on eBay and I still have contact info for a seller with 4000 series ISAS units. I think I actually would consider the independent units over straight axles if the price were right. Keeping my eyes open.​
I have yet to see someone use an ISAS unit in the aftermarket, but it'd be awesome to see!
 
02rexwi said:
JNHEscher said:
Highly appreciated, sir. I'll have more questions once we approach the time to purchase axles. Quite the situation we're dealing with over the house at the moment.

JD8420 and I were conversing about axle series and parts interchange for a while. I eventually found the info I was after in regards to the brake calipers and chambers. Figured I would have to wait until we bought a front/rear pair to swap park chambers on a steer axle to measure clearances.

JD also pointed me towards a 5000 series ISAS on eBay and I still have contact info for a seller with 4000 series ISAS units. I think I actually would consider the independent units over straight axles if the price were right. Keeping my eyes open.​
I have yet to see someone use an ISAS unit in the aftermarket, but it'd be awesome to see!​
Totally after some, but man are they expensive because they're much newer. 4000 series should work well under the weight of the bus. 5000 has some neat options.
 
Grendel said,
JNHEscher said:
Totally after some, but man are they expensive because they're much newer. 4000 series should work well under the weight of the bus. 5000 has some neat options.​
Did I miss what you wanted to do with them?

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Grendel said:
Did I miss what you wanted to do with them?​
Not to worry. I haven't explained it yet. Ultimately, I'm after three steer axles. The kicker is that everyone sells them in front steer/rear straight pairs only. I've been watching auctions. The pairs are in our price range, yet I can't work out a solo flight out to the east to pick them up with a Uhaul or something. Two narrows in the rear and a wide up front fit perfectly.
 
02rexwi said,
JNHEscher said:
Totally after some, but man are they expensive because they're much newer. 4000 series should work well under the weight of the bus. 5000 has some neat options.​
I imagine the 4000 series are probably from a Textron TAPV vehicle and the 5000 series is probably from a Maxxpro DASH. Got any links to share?
 
02rexwi said:
I imagine the 4000 series are probably from a Textron TAPV vehicle and the 5000 series is probably from a Maxxpro DASH. Got any links to share?​
I'm not familiar enough with all the various military vehicles available, but I believe you're right. The 5000 is off the Maxxpro. I've been getting most of my info off of AxleTech's website. I've read that the 4000's are huge. The 5000 must be massive and very worthy of the load of a converted coach bus.
 
02rexwi said,
JNHEscher said:
I'm not familiar enough with all the various military vehicles available, but I believe you're right. The 5000 is off the Maxxpro. I've been getting most of my info off of AxleTech's website. I've read that the 4000's are huge. The 5000 must be massive and very worthy of the load of a converted coach bus.​
What was the GVWR of the front/rear of the bus?
Any idea what kind of weight you'll be running at?
 
02rexwi said:
What was the GVWR of the front/rear of the bus?
Any idea what kind of weight you'll be running at?​
How's that? Judging by what I've seen of coach bus conversions over the last year, I'd estimate our total weight to be 30,000 +/-3,000.

496.jpg
 
02rexwi said,
JNHEscher said:
How's that? Judging by what I've seen of coach bus conversions over the last year, I'd estimate our total weight to be 30,000 +/-3,000.​
You'd be good with the 4000 series.
Brakes may not be ideal though. I believe you'll have hydraulic brakes on the 4000 series, but they could be converted to air fairly easily.
 
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