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Brake upgrades using factory parts for GMT-400(88-00 OBS), and 94-99 DODGE 2500/3500

Husker6.5 said:
Yeah, to get the spare out of the rear cargo area, it was mounted underneath in the rear like the pickups. To maintain fuel capacity like the old Burbs, twin tanks. There's a couple of threads on here dealing with in-op fuel transfer and gauge issues between tanks.
Click to expand...
I wonder why they didn't go with a door mount like a Jeep.
 
Husker6.5 said:
I'm really surprised, as a professional mechanic, that you aren't familiar with the weaknesses of the GMT-400/6.6TD platform and the tried and true fixes to address those issues.
Click to expand...

I am familiar enough with the multiple aggravations and expense of a diesel that I purposely bought a 7.4 truck.


Husker6.5 said:
All factory steering geometry is maintained, and as with all front end work you put it on an alignment rack and set the toe-in, caster and camber just as you would with a GMT-400 front end if you'd just done the upper and lower ball joints. In fact, there are direct parts interchange between the two different front ends such as the ball joints.

If you want really improved front braking, just bite the bullet and do the GMT-800 conversion and quit piddling around with a potentially fatal, dangerous mish-mash of SRW/DRW calipers, rotors and pads that are not meant to work together to gain only minimal improvements in stopping power.
Click to expand...

That may or may not be true, or some parts of it may or may not be true. One thing that is true is that 95% of the people talking on the internet do NOT know what they are talking about, or partially don't know what they are talking about. That does NOT mean that I am saying that is true in this case or your case, or that you don't know what you're talking about. What I am saying is that I'm not going to go out and spend a bunch of time and money carving up a perfectly good truck just because of one thread on the internet somewhere without further research on my part.

I don't see how you can claim with any certainty that putting on DRW calipers is more potentially fatal and a mish mash than swapping out 10 other parts from a different truck, reaming parts in a potentially imprecise way, etc.

The ONLY potential danger I see from the DRW front calipers would occur if the pads were allowed to wear excessively. On top of that, I've seen DOZENS of over extended caliper pistons in my days, and none of them were fatal. That doesn't mean that a fatality hasn't occured somewhere from this condition. But given my credentials, what do you think the likelihood is that I will let my pads go that far?

It will be a cheap, low risk improvement that may or may not turn out to be satisfactory to me. We'll see.



Husker6.5 said:
Yeah, with that 7.4L in it, there isn't much he can do to improve power, performance or longevity without dumping some serious bucks into it with little gain. Not like gaining 100 hp and 200 lb/ft with a 6.5 and getting a more reliable motor in the process.
Click to expand...

I don't need a 100 more horsepower or 200 more ft. lbs. I need a reliable dependable truck that operates as designed.
So far it has given me 290,000 miles of dependable service. It has never had brown or black oil in it or run low, or overheated. It uses no oil still, and purrs as it should. I expect to get another 100-200,000 out of it at this rate. Seems pretty reliable so far by any measure.

When I need more power or torque I go hop in my Olds that has 550 hp and 675 ft. lbs in a 3500 lb. car.



Tom
 
jrsavoie said:
I wonder why they didn't go with a door mount like a Jeep.
Click to expand...
I looked at doing that with my Burb. With the size of the LT 245/75-16 tire, you have to choose between either blocking the Driver's side taillight or the door handle on the Passenger side barn door, or both, not to mention almost totally obstructing one rear door window or the other, no matter how you mount it. Also, unlike the rear barn door mounted spare on my old '85 G20 Chevy conversion van, the vertical distance between the two hinges (the mounting points for the spare's 'arm') the hinges on the Burb are really close together, which would create weight/leverage issues with that big ol', heavy spare. I have thought about fabricating some sort of 'drop down' spare mount, but that too would block the door handle and when dropped down for barn door access, would interfere with any trailer tongue you have hitched up.
 
Husker6.5 said:
I looked at doing that with my Burb. With the size of the LT 245/75-16 tire, you have to choose between either blocking the Driver's side taillight or the door handle on the Passenger side barn door, or both, not to mention almost totally obstructing one rear door window or the other, no matter how you mount it. Also, unlike the rear barn door mounted spare on my old '85 G20 Chevy conversion van, the vertical distance between the two hinges (the mounting points for the spare's 'arm') the hinges on the Burb are really close together, which would create weight/leverage issues with that big ol', heavy spare. I have thought about fabricating some sort of 'drop down' spare mount, but that too would block the door handle and when dropped down for barn door access, would interfere with any trailer tongue you have hitched up.
Click to expand...
The trailer hitch access is an issue on the Jeep. Maybe a swing frame like I have seen on other vehicles would work.
 
Last edited:
@C30454 Let's see, the reason you came to this forum in the first place was for advice for a problem you didn't have a solution for/advice on your solution. You don't like the advice you got because it conflicts with your perception of your ideal 'fix', fine. But bear this in mind, you already admitted you had no clue about parts interchangeability because it wasn't available in the 'factory' sources. So you have 20-30 years experience wrenching in a GM dealership, I take it? Well, we have people on here who worked extensively directly with GM's engineers on the R&D of the 6.5TD/GMT-400 platform, as well as at least one former GM engineer. The GMT-800 platform was the engineering evolution of the GMT-400 platform, and like all bean-counter driven corporate things, parts carryover to reduce costs was part of the equation. Thus, not only do both platforms use the same ball joints, the height of the steering knuckles pivot point to pivot point are the same. The only modification needed is a light taper reaming of the knuckles to fit the outer tierod ends, and you have what is a pretty much bolt on VAST improvement in front stopping power over the GMT-400 system, and FAR safer than the cobbled together conglomerate of mis-matched application parts that is inherently dangerous you seem to favor.

And it is not A thread, it's multiple threads of people who have done the conversion, step by step, with excellent results. @Big T just chimed in with how he's had 30K miles trouble free with his conversion.

Yet, you still think that a mish-mash of various application parts, that could turn out to be fatal if they aren't checked regularly and happen to fail, is some how better than an integral unit, with far better braking capabilities, and only one, slight modification needed to work? You want to stay all GMT-400 parts because it's your DD 'baby'? Then buy aftermarket drilled/slotted rotors and high friction, severe duty pads for it and put them on to get slightly better stopping ability, or won't you because they're not Factory parts and you don't know how 'good' they are?

Like I said before and others have done, the conversion is all GM and is essentially bolt-on to do with one slight modification and FAR safer than what you propose using mismatched rotors/calipers/pads. The GMT-400 to GMT-800 front brake/knuckle conversion is no more different than when I took my ex-girlfriend's '68 Cutlass Convertible and converted it from straight hydraulic drums all around to power front disc brakes 3 years before any aftermarket kit was available, by going to parts yards to scrounge find an A-Body donor for the correct knuckles off of a '71 Chevelle 4-door, a disc/drum proportioning valve off of a '69 VistaCruiser and new calipers/Master Cylinder/booster/hoses from the parts store, PowerStop drilled rotors and pads, SSBC stainless hardlines and gee, power disc brakes, better than factory, on a car that didn't come equipped that way from the factory!

And like I said before, the GMT-800 conversion is NO different than sticking a Mustang front end under a 32 Ford T-bucket street rod, or are you saying that a company like Speedway Motors is wrong and doesn't know what it's doing in offering that conversion in a Street Rod application? Think hard before you answer that question. The GMT-400 to GMT-800 conversion is Factory Parts to Factory Parts and was the GM Engineering Department's answer to using the heavier Duramax/Allison combo (which, BTW, WAS originally intended for the GMT-400 platform before the higher-ups decided that an all-new drivetrain deserved an (almost) all-new platform to debut in.

Bottom line, the GMT-800 conversion is safe and VERY effective in increasing your front braking ability, FAR more effective than the inherently unsafe caliper/rotor/pad mish-mash of parts you propose. What we propose isn't some pie-in-the-sky 'what if'? It's a proven, road tested, long-term, all GM parts fix to the inherently weak GMT-400 front braking problem.

If you don't like the answer, don't ask the question, especially if you appear to have your mind already made up to your answer before asking the question. We have tons of accurate knowledge to share on here about the GMT-400 and GMT-800 platforms, all drivetrain combinations, and fixes that GM's engineers couldn't foresee at the time of design for problems that cropped up 10-20 years down the road.
 
jrsavoie said:
The trailer hitch access is an issue on the Jeep. Maybe a swing frame like I have seen on other vehicles would work.
Click to expand...
You mean an "A-frame", door hinge mounted spare carrier like on conversion vans, or a bumper-mounted post-type swing away mounted on a Ranch Hand-type bumper? Either of which still has all the taillight/rear window/door handle issues outlines above. Believe me, I've spent several years trying to find a way to get the spare out of the rear cargo compartment to free up more room and yet still keep it easily accessible without obstructing other functions like lights, vision or access. The best I can come up with is to roof mount the spare on my Burb, but I REALLY don't want to do that for multiple reasons. That, or an overly complicated, structurally inherently weak, door hinge mounted A-arm system with a secondary latch mounted to the passenger side barn door to swing the spare out of the way every time you wanted to open the passenger barn door so you can reach the handle. But that would mean that you have enough clearance on the driver's side to swing the spare out without hitting a car parked next to you, or enough clearance to the vehicle parked behind you, or a tree at a campsite, etc.
 
Husker6.5 said:
@C30454 Let's see, the reason you came to this forum in the first place was for advice for a problem you didn't have a solution for/advice on your solution. You don't like the advice you got because it conflicts with your perception of your ideal 'fix', fine. But bear this in mind, you already admitted you had no clue about parts interchangeability because it wasn't available in the 'factory' sources. So you have 20-30 years experience wrenching in a GM dealership, I take it? Well, we have people on here who worked extensively directly with GM's engineers on the R&D of the 6.5TD/GMT-400 platform, as well as at least one former GM engineer. The GMT-800 platform was the engineering evolution of the GMT-400 platform, and like all bean-counter driven corporate things, parts carryover to reduce costs was part of the equation. Thus, not only do both platforms use the same ball joints, the height of the steering knuckles pivot point to pivot point are the same. The only modification needed is a light taper reaming of the knuckles to fit the outer tierod ends, and you have what is a pretty much bolt on VAST improvement in front stopping power over the GMT-400 system, and FAR safer than the cobbled together conglomerate of mis-matched application parts that is inherently dangerous you seem to favor.

And it is not A thread, it's multiple threads of people who have done the conversion, step by step, with excellent results. @Big T just chimed in with how he's had 30K miles trouble free with his conversion.

Yet, you still think that a mish-mash of various application parts, that could turn out to be fatal if they aren't checked regularly and happen to fail, is some how better than an integral unit, with far better braking capabilities, and only one, slight modification needed to work? You want to stay all GMT-400 parts because it's your DD 'baby'? Then buy aftermarket drilled/slotted rotors and high friction, severe duty pads for it and put them on to get slightly better stopping ability, or won't you because they're not Factory parts and you don't know how 'good' they are?

Like I said before and others have done, the conversion is all GM and is essentially bolt-on to do with one slight modification and FAR safer than what you propose using mismatched rotors/calipers/pads. The GMT-400 to GMT-800 front brake/knuckle conversion is no more different than when I took my ex-girlfriend's '68 Cutlass Convertible and converted it from straight hydraulic drums all around to power front disc brakes 3 years before any aftermarket kit was available, by going to parts yards to scrounge find an A-Body donor for the correct knuckles off of a '71 Chevelle 4-door, a disc/drum proportioning valve off of a '69 VistaCruiser and new calipers/Master Cylinder/booster/hoses from the parts store, PowerStop drilled rotors and pads, SSBC stainless hardlines and gee, power disc brakes, better than factory, on a car that didn't come equipped that way from the factory!

And like I said before, the GMT-800 conversion is NO different than sticking a Mustang front end under a 32 Ford T-bucket street rod, or are you saying that a company like Speedway Motors is wrong and doesn't know what it's doing in offering that conversion in a Street Rod application? Think hard before you answer that question. The GMT-400 to GMT-800 conversion is Factory Parts to Factory Parts and was the GM Engineering Department's answer to using the heavier Duramax/Allison combo (which, BTW, WAS originally intended for the GMT-400 platform before the higher-ups decided that an all-new drivetrain deserved an (almost) all-new platform to debut in.

Bottom line, the GMT-800 conversion is safe and VERY effective in increasing your front braking ability, FAR more effective than the inherently unsafe caliper/rotor/pad mish-mash of parts you propose. What we propose isn't some pie-in-the-sky 'what if'? It's a proven, road tested, long-term, all GM parts fix to the inherently weak GMT-400 front braking problem.

If you don't like the answer, don't ask the question, especially if you appear to have your mind already made up to your answer before asking the question. We have tons of accurate knowledge to share on here about the GMT-400 and GMT-800 platforms, all drivetrain combinations, and fixes that GM's engineers couldn't foresee at the time of design for problems that cropped up 10-20 years down the road.
Click to expand...


I came and asked a few questions. Absolutely. Why? Because I don't have ALL the answers to everything. And, quite frankly, neither do you. The recommendation of drilled and slotted rotors proves that right there.

I NEVER said you were wrong. I NEVER said ANY of the recommendations or modifications recommended by you or others were wrong.

I DO ask tough questions. I DO question people's statements and claims. It's the only way to find out if people REALLY know what they're talking about. Usually, the only people who get offended by tough questions are people who don't have all the answers they claim to have, or it frosts their balls for a new guy to come and ask tough questions about claims because they like being the unquestioned authority.

I asked my questions respectfully. I stated the parameters of what I was willing to do to my vehicle, for reasons that are valid to me. I'm not telling you what to do or not with your vehicle. If you can't answer the questions, be respectful. If you don't like what I choose to do to my truck because you did your's differently, get over it. If you don't like fielding tough questions or you feel like it diminishes your status for people to ask questions, step aside. But be respecful.


Tom
 
Is there a write up on here for the front brake upgrade for gmt400 to 800? Didn't see any sticky on it in the drivetrain section. Came across this thread discussing it, but that's about it

Brake upgrade for my 98 K3500

After being less then happy with the braking on my 1998 K3500 GMC me an a friend of mine figured we could do something about it. After looking at a spindle from a 2000-2008 HD2500 we thought it was close enough to try it. Well it was some work but it does fit. Again this was done on Saturday...
www.thetruckstop.us
 
@Big T did one on his Burb conversion to GMT-800 brakes. There's a couple of others on here, too. Not as stickies. Hopefully, since the last Forum software update the Search function can find the older threads.
 
Thank you @Husker6.5, I found @Big T's thread, link here to help future folks:

GMT 800 Brake Conversion > Silverado HD 2500

Do the knuckles/spindles need to come from a 4wd HD 2500? I found a 2003 Silverado HD 2500 at a pick a part in Hesperia, which is about 1+ hour drive from me. It's definitely 8 lug, but I can't tell from the pictures if it's a 4 wd. Would prefer not to waste a trip out there...
www.thetruckstop.us

And here's a section of one of @n8in8or's threads also showing his foray into the upgrade:

1996 K2500 “Krovvy”

Thank you sir! It isn’t show quality, but it’ll do. Looks show quality to Me. of course, You should see some of My welds. LOLOLOL
www.thetruckstop.us

With regards to the 800 upgrade, a few questions for you pros, just to understand...

The GMT800 knuckles are reamed out to accept GMT400 ball joints and larger ES409RT outer tie rods, correct? Why can't GMT800 ball joints be used, clearance issues?

Also, it seems GMT400 outer tie rod can be re-used in GMT800 knuckle without reaming if one doesn't want to upgrade to beefier tie rod? @Big T mentions an adapter sleeve when keeping GMT400 tie rod, but what needs to be adapted if keeping tie rods stock?
 
DieselAmateur said:
With regards to the 800 upgrade, a few questions for you pros, just to understand...

The GMT800 knuckles are reamed out to accept GMT400 ball joints and larger ES409RT outer tie rods, correct? Why can't GMT800 ball joints be used, clearance issues?

Also, it seems GMT400 outer tie rod can be re-used in GMT800 knuckle without reaming if one doesn't want to upgrade to beefier tie rod? @Big T mentions an adapter sleeve when keeping GMT400 tie rod, but what needs to be adapted if keeping tie rods stock?
Click to expand...

Regarding the ball joint, I don't recall the differences, but I'm sure the body of the joint was a different size and it's much simpler to adapt the stud to the knuckle, which is a fairly forgiving taper stud, captured by a nut connection as opposed to a pressed fit connection of the ball joint body to the lower control arm.

This thread has a lot of good info regarding the tie rod ends. A GMT400 end will not bolt into a GMT800 knuckle.
GMT-400 to GMT-800 brake conversion tie rod discussion | The Truck Stop
 
Also, regarding the GMT800 knuckle swap, don't be intimidated by the idea of reaming the holes in the knuckles. I bought the tapered reamers from Speedway and they bored the holes lickety-split. In fact, if you're not careful, it's easy to go too far, they cut that well. Take your time and it goes fine. Before you start, make sure you have a solid 1/2" right angle drill to use..... I tried with a home-made 90 degree drive adapter that my dad had and it ruined my knuckles because it was wobbling and caused me to bore off-center. Once I got another pair of knuckles, I found a used Milwaukee 90 degree drill and it made the job super easy (bonus is I've used that drill for other jobs since then, so it wasn't a wasted investment). These are the reams I used:
Speedway Tapered Ball Joint Reamer, 7 Degree (speedwaymotors.com)
Speedway Tapered Ball Joint Reamer, 10 Degree (speedwaymotors.com)
 
n8in8or said:
Also, regarding the GMT800 knuckle swap, don't be intimidated by the idea of reaming the holes in the knuckles. I bought the tapered reamers from Speedway and they bored the holes lickety-split. In fact, if you're not careful, it's easy to go too far, they cut that well. Take your time and it goes fine. Before you start, make sure you have a solid 1/2" right angle drill to use..... I tried with a home-made 90 degree drive adapter that my dad had and it ruined my knuckles because it was wobbling and caused me to bore off-center. Once I got another pair of knuckles, I found a used Milwaukee 90 degree drill and it made the job super easy (bonus is I've used that drill for other jobs since then, so it wasn't a wasted investment). These are the reams I used:
Speedway Tapered Ball Joint Reamer, 7 Degree (speedwaymotors.com)
Speedway Tapered Ball Joint Reamer, 10 Degree (speedwaymotors.com)
Click to expand...

I did the top holes of the knuckle with a drill press. Inside (the knuckle) holes I used a 90 degree drill.
 
Big T said:
I did the top holes of the knuckle with a drill press. Inside (the knuckle) holes I used a 90 degree drill.
Click to expand...
I don't have the clamps like you do for my drill press table. I actually found that the 90 degree drill worked really nicely for the top and tie rod holes because having the body of the drill for a lever arm allowed me to have a lot of control while drilling the holes.....not as good as a drill press of course, but enough for me to have a good outcome.
 
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