DieselAmateur
She ain't revved 'til the rods are thrown...
Which holes are reamed 7 degrees and which are reamed 10*?
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Brake upgrades using factory parts for GMT-400(88-00 OBS), and 94-99 DODGE 2500/3500
- Thread starter THEFERMANATOR
- Start date
Husker6.5
135' diagonal 16:9HD, 25KW sound!
Ain't that a bit on the personal side?
Husker6.5
135' diagonal 16:9HD, 25KW sound!
But seriously, I believe that the 7° is the upper taper and 10° is the lower ball joint taper and is done because the diameters of the shafts of the new parts are larger. The taper reamer should already fit snugly into the bore, you are just carefully and slowly reaming a little bit deeper to widen the taper like another 1/16" to accommodate the larger tie rod and ball joint stud sizes. Besides, as far as the ball joint goes, FAR safer to bore the taper where the shaft is retained by a torqued and cotter pinned castle nut, than try to drill/machine/grind out an interference press-fit hole in a control arm to put the base of the ball joint into. The new taper should be the correct depth when a couple of threads are still below the surface, so the nut can pull snug before bottoming out on the tapered shaft.
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- Staff
- #164
The GMT800 brake upgrade is NOT an easy swap on a 2 wheel drive, it's not even really possible to swap 800 spindles onto a 2 wheel drive 400 without extensive modifications to the suspension and frame(just updated the op to clarify). Gmt800's all use a knuckle with a hub bearing as GM was cutting costs by making 2 & 4 wheel drives use the same parts. On the gmt400, 2 & 4 wheel drives used completely different spindles, a arms, geometry, even the frame width was different.
The single biggest reason you cannot do the gmt800 swap to a 2 wheel drive gmt400 is due to how the lower ball joints connect to the spindle. On 4x4 400's and all 800's the lower ball joint points down at the ground and the spindle mounts below the lower a arm, on 2 wheel drive 400's the ball joint points up at the sky and the spindle mounts pulling up on the ball joint. Some have modified the lower control arms to point the lower ball joint down, but then you MUST put an equal drop in the upper a arm to maintain suspension geometry, and you lift the vehicle doing it this way.
This is the only way to do it with a 2 wheel drive With stock parts. Otherwuse you can go with the wilwood calipers, but they're big $$$$.
And a shim to make up the 1/4" difference for the brake pads to drw calipers on a 1.25" rotor would make for one heck of a noise maker.
The single biggest reason you cannot do the gmt800 swap to a 2 wheel drive gmt400 is due to how the lower ball joints connect to the spindle. On 4x4 400's and all 800's the lower ball joint points down at the ground and the spindle mounts below the lower a arm, on 2 wheel drive 400's the ball joint points up at the sky and the spindle mounts pulling up on the ball joint. Some have modified the lower control arms to point the lower ball joint down, but then you MUST put an equal drop in the upper a arm to maintain suspension geometry, and you lift the vehicle doing it this way.
This is the only way to do it with a 2 wheel drive With stock parts. Otherwuse you can go with the wilwood calipers, but they're big $$$$.
Big brake kit (my way)
Just have time to post this real quick, will be back latter to add more. Anyway Ive working on a Big Brake Kit for the 88-2000 trucks. This set up is for the 6lug 2wd and "might" work on the 5 lug and 8 lug trucks also, but I need to check it out first. The stock rotor is 11.5" dia. I wanted...
www.thetruckstop.us
And a shim to make up the 1/4" difference for the brake pads to drw calipers on a 1.25" rotor would make for one heck of a noise maker.
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Big T
Well-Known Member
So the guff I got for being unwilling to convert my GMT400 C3500 2WD front brakes to a GMT800 setup was all for nothing?
Tom
- Staff
- #167
Yes, it is not an easy swap, and requires custom machining to make work. I know I've said this elsewhere, but it wasn't in my original post on it(which I've remedied). The gmt800 brakes ARE far superior to the gmt400, but for 2 wheel drive guys, it is not an easy bolt on swap Like it is for 4x4 guys. I need to go through and clean this post up and add more to it that I have learned since I 1st made it.
Just a little update for any other 1 ton 2wd SRW guys.
I put the larger DRW wheel cylinders in my truck and it made a noticeable improvement. Not so much with a light pedal, but if you bear down at all you can feel the extra braking from the rear. It is not overpowering, and the rears do not seem prone to unnecessary lockup at all. But they are a little stronger when you need them. I believe they should have left the factory this way. There seems to be no adverse side effects, only an improvement. The fact that my rear shoes were not worn out with 290,000 on them is a reasonable indicator that they were being under-utilized with the stock size SRW wheel cylinders.
I also put the larger piston front calipers on a few weeks later. My opinion on that is that there was also a very SLIGHT improvement in front braking power, but probably not enough to be worth the downside of the calipers being too wide to allow the pads to wear all the way without consequences, IMO. I will likely put them back to stock size at some point and try some more agressive pads.
Tom
I put the larger DRW wheel cylinders in my truck and it made a noticeable improvement. Not so much with a light pedal, but if you bear down at all you can feel the extra braking from the rear. It is not overpowering, and the rears do not seem prone to unnecessary lockup at all. But they are a little stronger when you need them. I believe they should have left the factory this way. There seems to be no adverse side effects, only an improvement. The fact that my rear shoes were not worn out with 290,000 on them is a reasonable indicator that they were being under-utilized with the stock size SRW wheel cylinders.
I also put the larger piston front calipers on a few weeks later. My opinion on that is that there was also a very SLIGHT improvement in front braking power, but probably not enough to be worth the downside of the calipers being too wide to allow the pads to wear all the way without consequences, IMO. I will likely put them back to stock size at some point and try some more agressive pads.
Tom
MrMarty51
Well-Known Member
Thank You for posting the information. That’ll help someone later on.
Oredigger97
New Member
Hey guys, long time listener, first time caller. I have been trying to track down the proportioning valve from the tsb on the suburbans. I checked with the dealer that sold and serviced my burb and we confirmed the tsb was not addressed and he searched the earth for me trying to find one with no luck. Any ideas on where to track one down at this point? I checked all over online, even eBay didn't have one. It looks like I may be down to junkyard trolling. Are there any visual differences or a code on the newer one I can use to find one. Thanks guys!
@Oredigger97 are you converting to disc or upgrading existing.. ? Personally I'm trying to find correct proportioning valve also but because I'm deleting a.b.s. ..
Husker6.5
135' diagonal 16:9HD, 25KW sound!
He's talking about the updated valve for rear drums.
Will L.
Well-Known Member
@Oredigger97
I would be getting an adjustable unit like the ones used on track cars.
Just do some test driving on gravel roads and such to get the lockup adjustment right.
I would be getting an adjustable unit like the ones used on track cars.
Just do some test driving on gravel roads and such to get the lockup adjustment right.
MrMarty51
Well-Known Member
@Oredigger97
Welcome to the truck stop.
Welcome to the truck stop.
Oredigger97
New Member
I'm not quite ready to go there yet, I'm under the assumption I would have to eliminate the abs if I go that route. My burb only has 73,000 miles on it and is pretty clean, so that will be a last resort.
Husker6.5
135' diagonal 16:9HD, 25KW sound!
@Oredigger97 That part (the upgraded proportioning valve) called for in the TSB for older Burbs was scarcer than hens teeth when the thread about it was written.
Iirc, a member on here had their local dealership parts guy do a nationwide search for the part and came up with like a couple at one dearlership, one at a couple of other dealerships and one at a couple of distribution warehouses and that was it. And that was a few years back before Covid. Not surprising that it's no longer able to be located now.
Since the TSB was for a retrofit, that means the change was made at the same time on the production line. I would assume that you would be able to find it on any post TSB-date Burbs in a parts yard, as well as a 2000 Escalade, which was just a 99 Burb with a different nose and plastic add-on body panels to make it a "Cadillac".
Iirc, a member on here had their local dealership parts guy do a nationwide search for the part and came up with like a couple at one dearlership, one at a couple of other dealerships and one at a couple of distribution warehouses and that was it. And that was a few years back before Covid. Not surprising that it's no longer able to be located now.
Since the TSB was for a retrofit, that means the change was made at the same time on the production line. I would assume that you would be able to find it on any post TSB-date Burbs in a parts yard, as well as a 2000 Escalade, which was just a 99 Burb with a different nose and plastic add-on body panels to make it a "Cadillac".
Oredigger97
New Member
Thanks Husker, I'll check the wrecking yards for a abs unit from a 2000 escalade, that might be the easiest way to find one.
Husker6.5
135' diagonal 16:9HD, 25KW sound!
No, iirc, it is NOT the ABS unit that was replaced under the TSB, it was the combination or "proportioning" valve on the back of the ABS unit that gets changed out. Bleeding an ABS is a royal P.I.T.A. without the proper equipment, whereas bleeding the proportioning valve it relatively simple. Here is a PDF attachment to an article on this very subject for 1990's Suburbans with the P/N's of the parts needed.