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Discussion Starter #1
I want to investigate the ultimate upgrade for the rear end in our 6.5L trucks.

Goals:
Disk brakes
Parking brake
Full floater
Minimal alterations/modifications
Minimal cost
Readily available

The problem that I see with most disc brake upgrades on a 14 volt is that there is no good parking brake. Also, I am looking to re-gear to 3.73 at the same time and I don't want to invest almost $1k into my stock setup.

So, I've thought about putting a Duramax rear end under my 6.5 truck, but I don't want to have to shorten my drive shaft. Recently, however, I found a 2005 Chevy C2500 with a 6.0 gas engine. It has a 14 bolt that looks identical to mine except that it has factory disc brakes with built-in parking brakes. I haven't found one with 3.73 gears yet though.

My question is, will this rear-end fit in my truck without shortening the drive shaft?
And what other modifications would be necessary?

I understand that new spring perches and shock mounts will be in order, but from my understanding GMT 800 rear ends are pretty readily swappable into GMT 400s. There may also be some difference in width?
 

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If i remember right width is the same between them both at least on 4wd versions. I don't know about 2wd or what your truck is. You will have to move the shock mounts. I think you will just have to get a conversion u-joint for the diff.
 

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Discussion Starter #3
Is there a difference between the GMT 800 and GMT 900 axles? It's there a specific year range I should look for and what about a proportioning valve for the disc brakes?
 

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Discussion Starter #4
If i remember right width is the same between them both at least on 4wd versions. I don't know about 2wd or what your truck is. You will have to move the shock mounts. I think you will just have to get a conversion u-joint for the diff.

Mine is a 1996 2wd extended cab long bed with 2 piece drive shaft.
 

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Discussion Starter #5
Has anyone done this or have experience?
 

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Just want to point this out;

Disc brakes; good for speeding around.. being spiffy... performance oriented. They are inferior to drums for pulling weight. If you plan on pulling any significant amount of weight go rear drum.

And before I get flack for this (I'm use to it) it's not that you CANT pull weight with discs; they just fail faster under loads. Bent discs/vibration/squishy brakes/ overheating issues etc.

There are reasons why commerical trucks use drums and not discs. Hydraulic brakes fail the fastest (they trans heat the best). Air over hydraulic in the middle. Air brakes last the longest(air is an insulator and does not transfer heat very well). All about heat transfer. Drums vs discs / about contact area. You have much more contact area on drums.

The reason the modern trucks have 4 wheel discs is due to consumer marketing... and consumers just not knowing any better. What can I say? Discs are 'popular'. :hehe:

:thumb: hope this helps...
 

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I want to investigate the ultimate upgrade for the rear end in our 6.5L trucks.

Goals:
Disk brakes
Parking brake
Full floater
Minimal alterations/modifications
Minimal cost
Readily available

The problem that I see with most disc brake upgrades on a 14 volt is that there is no good parking brake. Also, I am looking to re-gear to 3.73 at the same time and I don't want to invest almost $1k into my stock setup.

So, I've thought about putting a Duramax rear end under my 6.5 truck, but I don't want to have to shorten my drive shaft. Recently, however, I found a 2005 Chevy C2500 with a 6.0 gas engine. It has a 14 bolt that looks identical to mine except that it has factory disc brakes with built-in parking brakes. I haven't found one with 3.73 gears yet though.

My question is, will this rear-end fit in my truck without shortening the drive shaft?
And what other modifications would be necessary?

I understand that new spring perches and shock mounts will be in order, but from my understanding GMT 800 rear ends are pretty readily swappable into GMT 400s. There may also be some difference in width?
The newer axle is wider but not much, the u joint is different 1410 vs 1350, spring pads you already know.
 

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Discussion Starter #8
That's good to know about pulling weight. However, I think the most that any of these old 6.5L trucks are specified to pull is 11,000 or 12,000 lbs. I do occasionally pull 14,000 lbs, but most of the time I just fill the bed or use a tag along trailer. Do you think there is potential for discs to fail at these weights? I plan on using a 14 bolt from a newer gas truck, I'm not sure what size discs those are or the ratings. Also, would that require a new master cylinder or proportioning valve?
 

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Discussion Starter #9
Also, another concern is weight savings and fuel mileage. Do you think either of these will be significant with this conversion?
 

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Just want to point this out;

Disc brakes; good for speeding around.. being spiffy... performance oriented. They are inferior to drums for pulling weight. If you plan on pulling any significant amount of weight go rear drum.

And before I get flack for this (I'm use to it) it's not that you CANT pull weight with discs; they just fail faster under loads. Bent discs/vibration/squishy brakes/ overheating issues etc.

There are reasons why commerical trucks use drums and not discs. Hydraulic brakes fail the fastest (they trans heat the best). Air over hydraulic in the middle. Air brakes last the longest(air is an insulator and does not transfer heat very well). All about heat transfer. Drums vs discs / about contact area. You have much more contact area on drums.

The reason the modern trucks have 4 wheel discs is due to consumer marketing... and consumers just not knowing any better. What can I say? Discs are 'popular'.


/forum/images/smilies/thumb.gif hope this helps...
, I agree with this guy
 

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I disagree on the drum vs disc issue, too.
 

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I decided "what's the point in it"... :hehe:

One does what one will based on what one knows. Didnt mean for it to become an "issue". Just speaking from experience hauling serious weight...60,000lbs current to date record / trailer weight included with 18,000rig @ 78k gcvwr... :) horrraaayyy heavy haul!

I noticed issues with the 2015 lml (8300lbs) with a 40' big tex (10k) gcvwr 18300. Truck (had) rear discs. Elect drum trailer brakes. With a 7k payload, 25300 gvwr... serious issues with overheating especially on grades above 5%. Bout my only complaint with modern rigs. The manumatic transmissions arent bad. The allison in the lml works like a champ. Most impressed with it. Bout my only complaint is the chinky weak @$$ rear discs. Now converted to drums. :thumb: the discs got squishy... lots of pedal vibrations.. etc... even with proper braking (5on and 5off) and transmission control... some grades can last several miles. I'd personally like to stay off the runaway ramps. :thumb:

Before the disc conversion I'd use the equivalent of the trailer handbrake to help slow the rig on 8%+ max gain. Eeek

As for comparison to large airplanes and road rigs... I know nothing about aeronautics and airplanes (never will) but... to me... apple's to oranges.

Merry Christmas everyone. :thumb:
 
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Discussion Starter #15
I decided "what's the point in it"...


One does what one will based on what one knows. Didnt mean for it to become an "issue". Just speaking from experience hauling serious weight...60,000lbs current to date record / trailer weight included with 18,000rig @ 78k gcvwr... /forum/images/smilies/smile.gif horrraaayyy heavy haul!

I noticed issues with the 2015 lml (8300lbs) with a 40' big tex (10k) gcvwr 18300. Truck (had) rear discs. Elect drum trailer brakes. With a 7k payload, 25300 gvwr... serious issues with overheating especially on grades above 5%. Bout my only complaint with modern rigs. The manumatic transmissions arent bad. The allison in the lml works like a champ. Most impressed with it. Bout my only complaint is the chinky weak @$$ rear discs. Now converted to drums. /forum/images/smilies/thumb.gif the discs got squishy... lots of pedal vibrations.. etc... even with proper braking (5on and 5off) and transmission control... some grades can last several miles. I'd personally like to stay off the runaway ramps. /forum/images/smilies/thumb.gif

Before the disc conversion I'd use the equivalent of the trailer handbrake to help slow the rig on 8%+ max gain. Eeek

As for comparison to large airplanes and road rigs... I know nothing about aeronautics and airplanes (never will) but... to me... apple's to oranges.

Merry Christmas everyone. /forum/images/smilies/thumb.gif
It looks like jnlperformance's ideas are substantiated by the linked article. It looks like disc brakes are superior for stop and go and frequent breaking applications, however, drum brakes are better for long haul over the road trucks and long grades.

Luckily for me, I have two one tons a SRW and a DRW that will be for my heavy towing. I still plan on upgrading to a newer axle with disc brakes on my 3/4 ton which I use for long distance traveling with low weight and short distance traveling with heavy weight. Also, I live in Louisiana where there are no grades for when I'm towing.

In my application, I'm looking to re-gear to 3.73 gear ratio and have the most fuel efficient setup possible, which I think disc brakes will help...

So, from anyone who has done this, any tips tricks or tutorials would be greatly appreciated!

Merry Christmas
 
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Anyone old enough to have driven a car or pickup with 4-wheel drum brakes, and drove through rain-soaked roads in that car or truck, will understand one of the primary advantages of disk brakes.
 

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Discussion Starter #17
So, I have found a 2003 Chevy Express 3500 that came with a 6.0L gas engine and GT4 (3.73 gear ratio) 14 Bolt rear end with disc brakes. I plan on going to pull-a-part Tuesday to claim my prize. The calipers have already been taken, so I will get new ones and also have to figure out new brake lines.

My question is there a difference in the wheel mounting surface distance between my current 1996 2wd truck 14 bolt and this newer van 14 bolt?
 

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Discussion Starter #18
It looks like I will need a combo u joint as the newer trucks have a 1410 u joint in them vs the 1350 in my older setup.

Also, most articles that I read say that the van axle is 2" wider and the spring perches are about 1" off with the possibility of just prying the springs into place without redoing spring perches.

One of the shock mounts will have to be relocated to the front of the axle as vans have both mounted on the back.
 

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Discussion Starter #19
Quote from Turbonator

Quote from Turbonator:
"we used a diff from a 2000 savana when we changed ours to dually, the spring perches are slightly narrower on the van, and the shock both mount on the same side of diff, so you will have to cut one off and swap sides, IIRC it was the driver side one... as for the spring pads, i just used a small bar to pry out the spring pack until the alignment stud dropped into the hole, its less than one inch of difference... hope this helps..."
 

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I decided "what's the point in it"... :hehe:

One does what one will based on what one knows. Didnt mean for it to become an "issue". Just speaking from experience hauling serious weight...60,000lbs current to date record / trailer weight included with 18,000rig @ 78k gcvwr... :) horrraaayyy heavy haul!

I noticed issues with the 2015 lml (8300lbs) with a 40' big tex (10k) gcvwr 18300. Truck (had) rear discs. Elect drum trailer brakes. With a 7k payload, 25300 gvwr... serious issues with overheating especially on grades above 5%. Bout my only complaint with modern rigs. The manumatic transmissions arent bad. The allison in the lml works like a champ. Most impressed with it. Bout my only complaint is the chinky weak @$$ rear discs. Now converted to drums. :thumb: the discs got squishy... lots of pedal vibrations.. etc... even with proper braking (5on and 5off) and transmission control... some grades can last several miles. I'd personally like to stay off the runaway ramps. :thumb:

Before the disc conversion I'd use the equivalent of the trailer handbrake to help slow the rig on 8%+ max gain. Eeek

As for comparison to large airplanes and road rigs... I know nothing about aeronautics and airplanes (never will) but... to me... apple's to oranges.

Merry Christmas everyone. :thumb:
Not knocking your choice, but...what components did you use, since your truck has ABS and Stabilitrac, and the newer bolt pattern? I don't recall seeing any drum setups with that bolt pattern for the hub.
 
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