When was the change to rear disc?

Blackdog

Blackdog

Hillbilly Deluxe
Joined
Jan 31, 2008
Messages
801
I was looking up under my new 01 today and noticed it had drums in the rear. The 01 parts truck I had were discs on the rear. Both are dana 80. When was the switch? I'm guessing 01.5 but I thought the change was in 00.
 
can you take the disc brakes off and install them on the eariler drum brake style with no problems
 
dirtpoor said:
can you take the disc brakes off and install them on the eariler drum brake style with no problems
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No, the disc brake Dana axle more similar to AAM than old drum brake DAna axle
 
Disk brake 2001s started rolling off the assembly line July or August 2000, don't remember for sure.
 
i was under the impression you could not swap the disc brake hardware but had to swap the complete axle. as i did in my 99 and early 01 june 2000
 
How hard is it to swap the axle from one with drums to one with discs? do you need to swap brake lines?? I just scored a dana 70 with discs for cheap... I am jumping on it, as my ring and pinion is shot in my Dana 80, and the drums to little to nothing to stop my 9,000 lb Baja Outlaw boat..
 
I went from a drum d70 to a disc d80 and it is just a bolt up. I did have to find a way to tighten up my e-brake cable because I didn't swap what was on the axle end for those I just left the 80 with what it had. I did find the brakes weren't as tight because the disc have the proportioning valve or what not under the hood but it still stops good and I may add that at some point.
 
C. Harlan said:
How hard is it to swap the axle from one with drums to one with discs? do you need to swap brake lines?? I just scored a dana 70 with discs for cheap... I am jumping on it, as my ring and pinion is shot in my Dana 80, and the drums to little to nothing to stop my 9,000 lb Baja Outlaw boat..
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have you done the chevy 1 ton wheel cylinder upgrade?
 
C. Harlan said:
How hard is it to swap the axle from one with drums to one with discs? do you need to swap brake lines?? I just scored a dana 70 with discs for cheap... I am jumping on it, as my ring and pinion is shot in my Dana 80, and the drums to little to nothing to stop my 9,000 lb Baja Outlaw boat..
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The lines on the axle will be different, but there shouldn't be a problem hooking up the flex hose from the frame (don't quote me).

The master cylinder should be changed also, as I believe this is where the metering valve is located. It is not needed with disc brakes.
 
j-rod said:
The lines on the axle will be different, but there shouldn't be a problem hooking up the flex hose from the frame (don't quote me).

The master cylinder should be changed also, as I believe this is where the metering valve is located. It is not needed with disc brakes.
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The lines on the axle are different from the style of brakes but the flex hose will still bolt right up where the old one came out with no issues. The metering valve that the 98's and I don't what other years had is above the rear axle and metered the brake pressure to the rear brakes based on the load applied to the back of the truck (more load more brake pressure etc.) and I just unbolted and disconnected it and took it out when I took out the old axle and you do not have to swap any lines or hoses from the old axle to the new one. Drum to disc I mean
 
Blackdog said:
The lines on the axle are different from the style of brakes but the flex hose will still bolt right up where the old one came out with no issues. The metering valve that the 98's and I don't what other years had is above the rear axle and metered the brake pressure to the rear brakes based on the load applied to the back of the truck (more load more brake pressure etc.) and I just unbolted and disconnected it and took it out when I took out the old axle and you do not have to swap any lines or hoses from the old axle to the new one. Drum to disc I mean
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The metering valve you are referring to is something different entirely. I believe that is what is called the "rear height sensing valve". It may change the distribution front to back - I don't know its exact function, as I do not have one and have not looked into it.

The metering valve I am describing keeps 5-10 psi of pressure at the wheel cylinders at all times regardless of vehicle height. Disc brakes do not need this valve.

Thanks for verifying my flex hose comment.
 
j-rod said:
The metering valve you are referring to is something different entirely. I believe that is what is called the "rear height sensing valve". It may change the distribution front to back - I don't know its exact function, as I do not have one and have not looked into it.

The metering valve I am describing keeps 5-10 psi of pressure at the wheel cylinders at all times regardless of vehicle height. Disc brakes do not need this valve.

Thanks for verifying my flex hose comment.
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See I am not sure of the metering valve your talking about. I never looked into it unless it is the proportioning valve that I mentioned but it is the disc trucks that had that right? I do know that since the swap to rear disc I don't feel them dragging or holding me back and the valve your talking about should make them do that.
 
Blackdog said:
See I am not sure of the metering valve your talking about. I never looked into it unless it is the proportioning valve that I mentioned but it is the disc trucks that had that right? I do know that since the swap to rear disc I don't feel them dragging or holding me back and the valve your talking about should make them do that.
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The proportioning valve is the first thing the lines run into after the master cylinder - regardless of 4 wheel disc or disc/drum. (If the truck had the rear height valve it may not.)

I don't think you would feel them drag. On other vehicles (not specific to these series trucks) you would just burn out the rear pads faster than normal.

I have had all 4 of my calipers drag (at different times) and you can't feel that - you will only get a hint of hot brake smell when you walk by the caliper at fault. Unless it gets really bad - EGTs go up, truck pulls, and the brake smell is overpowering in the cab (only happened on 1 caliper).

This is where things can get funny, and I'm not 100% sure for these trucks. The metering valve is usually stuck somewhere in another component - master cylinder is a common place, but it also can be put in the proportioning valve. I would guess that it also could have been put in the rear height sensing valve (like I said ... not familiar with them) which would explain why you have not had any issues with your swap. I'll see what I can dig up in my service manual tonight.
 
Sounds good, I'll do some digging because now I just have the curiosity and want to know.
 
Here are two images right out of the service manual:

brakeimage1.jpg


brakeimage2.jpg


It is not a 100% match to what I said above, but it is close.
 
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