Ctis versus regular axles

[Csm Davis]

I am thinking about rebuilding a set of axles for my ultimate tractor build. The A2 axle has a flat bottom which is better clearance but less oil volume and the parts for the hubs cost more and are harder to find but it has CTIS. The question is on a mostly street driven truck is the CTIS axle worth the extra in rebuild cost and if not can the nonCTIS hubs be used on a A2 axle?

 

[infidel got me]

Jeff- I removed the ctis off mine. Plugged the ports with fittings, gutted the plastic ctis parts from the hubs and ran old style seals( non ctis seals) never had a problem. You should be able to do the same. It's been a while but on the spindle I seem to remember grinding a small part (think it was a air port) and filling the hole with silicone. It was all straight forward stuff- it sounds worse than it is. Hope this helps out and good luck!

 

[JohnnyBM931A2]

There are differences between A1 and A2 axle housings? I had no idea.. Do you have any comparison pictures?

 

[infidel got me]

Axle

I know the front drums(A1) are held on by the bearings, which makes it a pain in the pants to remove drum. The A2 drums slide off without messing with the bearings. Don't quote me on this, but if memory serves correctly the bearings and seals are different. (ON FRONT) As far as I know the overall axle is the same.

 

[JohnnyBM931A2]

He was saying that the A2 axle has a flat bottom, unlike the earlier axles. I'm just trying to figure out what he is referring to..

 

[74M35A2]

Yes. The differential area of CTIS axles do have a flattened bottom.

 

[JohnnyBM931A2]

Yes. The differential area of CTIS axles do have a flattened bottom.

Hmm.. Interesting

 

[74M35A2]

Not really.

 

[JohnnyBM931A2]

It is to me. I never knew there was a difference. I assumed 5 ton axles were 5 ton axles.. I thought the only differences were the hubs.

 

[74M35A2]

Your name and sig are A2, so you should have CTIS and flat bottomed axle housings. Prior gen were not flat on the bottom, instead they are fully rounded like a basketball. You probably thought they were all flatties like yours.

 

[JohnnyBM931A2]

Yup. Only ever been around my A2 tractor, never an original M939 or A1. I've certainly seen plenty of pictures, but I never paid attention to the profile of the axles.

Yet another item to add to the list of reasons why the A2's are better

 

[Csm Davis]

Jeff- I removed the ctis off mine. Plugged the ports with fittings, gutted the plastic ctis parts from the hubs and ran old style seals( non ctis seals) never had a problem. You should be able to do the same. It's been a while but on the spindle I seem to remember grinding a small part (think it was a air port) and filling the hole with silicone. It was all straight forward stuff- it sounds worse than it is. Hope this helps out and good luck!

Okay so the seals work are the bearings the same?

 

[infidel got me]

Okay so the seals work are the bearings the same?

Jeff- as far as I know the ctis axle bearings vs. the a1 bearings are different. I did do a little research on part #s and they did come up different. Physically, I have not tried to compare either- Idk if the ft. axle housing (where the bearing rides) is different or the race itself is different? Anyone out there in the know have the answer?

 

[adamsoffroadperformance]

The races in the hubs are the same for all the 5ton trucks even the 800 series. the bearings cones on 800 series and the non ctis 900's are the same. the spindle on the ctis is thicker so they use a different bearing cone. and the ctis axles use a different hub seal you can use the old style airbrake hubs and hub seal on a ctis spindle but you will need to get the sleeves they used on the 800 and 900 series rear housings and put that on the ctis spindle like a speedy sleeve or the seal won't seal the hub. you can put the old 800 series hubs on the ctis spindle too just like with the air brake hubs but you wouldn't be able to put the airbrakes on it.

 

[adamsoffroadperformance]

Jeff- I removed the ctis off mine. Plugged the ports with fittings, gutted the plastic ctis parts from the hubs and ran old style seals( non ctis seals) never had a problem. You should be able to do the same. It's been a while but on the spindle I seem to remember grinding a small part (think it was a air port) and filling the hole with silicone. It was all straight forward stuff- it sounds worse than it is. Hope this helps out and good luck!

you said you used the non ctis seals. you mean the hub seal? ifso and you didn't add the seal sleeves onto the ctis spindle they used on the older rear axles then your seal isn't properly sealing the hub and spindle.

 

[74M35A2]

Wow, there is some experience in there.

 

[infidel got me]

Put well over 2k on it, pulled r/rear to replace abs sensor and didn't see any problem. No leaks or water intrusion. Maybe just lucky?

 

[Csm Davis]

Dragging this back to life. So a couple more questions if you want to run wet hubs instead of packing with grease can't you just leave out a inner seal? I understand why the military ran packed hubs to help stop water intrusion, but on a hwy truck the oil bath is better, don't want opinions on this but can and how it can be done.

sent from my decrepit fingers

 

[74M35A2]

Can be done on rears only, and is done by leaving the rear outer hub oil/grease seal(s) off. For non-CTIS hubs, this is all that would be needed to do. Don't remove the inner hub oil/grease seal or all the bearing oil will drain onto your brakes then the ground. On CTIS rear hubs, only the outer bearing would be oil lubed if this conversion was done. You would need to remove both CTIS inner (middle, really) hub AIR seals and then plug the CTIS air passage port in the hub in order to oil lube the inner bearing. Yes, can be done. Not possible to retain CTIS and oil bath rear hub inner and outer bearings simultaneously. There are 4 total hub seals on CTIS hubs. Outer-most and inner-most are oil/grease seals. The middle 2 are air seals for passage of air from spindle to hub as it rotates. No opinions? You're no fun...

 

[Csm Davis]

Okay smarty pants let the opinions fly. What would y'all build for over the road trucking if you could only use 5ton Rockwell axles?

sent from my decrepit fingers