GMT 800 Brake Conversion > Silverado HD 2500

[Big T]

Pics?

Sorry for the delay but here are some pics of the issue. We might have to look at swapping in forged lower control arms.

 

[ryeguy2006a]

Did you ever figure out why the knuckles don't rub on your 1999, but do on the 1994?

 

[Big T]

Did you ever figure out why the knuckles don't rub on your 1999, but do on the 1994?

I would say they don’t rub, it’s just that the stops on the forged LCA allow more steering travel.

Haven’t installed the forged LCAs yet. Hope to get to that this year. Still a lot on my plate and still recovering from foot surgery.

 

[ryeguy2006a]

Ok thanks for the clarification. And I thought I read somewhere that the later model OBS 2500 trucks all came with the forged lowers stock?

Thanks for this thread, so much great information here. I can't wait to do this swap ok my truck!

 

[ryeguy2006a]

BigT, another question, did you have to use the GMT800 axles or can you re-use the stock GMT400 axles? I've seen a few other people mention that you have to swap to the later model axles for a smaller diameter or something?

 

[THEFERMANATOR]

There's a company out there making an adapter to bolt the new style disc brakes on in place of the older drums. Otherwise you need to weld on a new bracket to attach the disc brake bracket or swap axles and reweld the mounting brackets.

 

[ryeguy2006a]

Thanks for the quick reply Ferm. I should have specified though, I'm asking about the front brakes. I saw that company out there for the conversion brackets for the rear drums, but I'm pretty happy with my stock drums at the moment.

 

[Big T]

BigT, another question, did you have to use the GMT800 axles or can you re-use the stock GMT400 axles? I've seen a few other people mention that you have to swap to the later model axles for a smaller diameter or something?

Re-use the existing front GMT400 axles. They are an exact fit.

 

[ryeguy2006a]

Thank you Big T!! That is just the news I wanted to hear. I'm hoping to get my truck in for the swap in the next few months. I'll report back when I do.

 

[Turbo6]

Just found this posting. Its awesome great info. I never knew of this. And after almost have an oh Sh++ moment this weekend with a loaded up truck and trailer attached and a guy cutting me off on his bike and stopping 10 feet later for a yellow lights. I need to do this.

 

[Will L.]

Just found this posting. Its awesome great info. I never knew of this. And after almost have an oh Sh++ moment this weekend with a loaded up truck and trailer attached and a guy cutting me off on his bike and stopping 10 feet later for a yellow lights. I need to do this.

Welcome. Only thing better than going when you want to is stopping when you need to.

 

[ryeguy2006a]

I just finished up my swap last weekend and it really is night and day different. The swap really wasn't bad at all. For me the biggest time consumer was swapping out the upper ball joint. Those damn rivets were a pain... I changed out both upper and lower ball joints, used the 409ES outer tie rods and had about 10 hours in the swap over two days. Some of that time was power washing/painting the new spindles, and a good 3-4 hours was messing with the upper ball joints on both sides. If I were just straight swapping the spindles, it should have taken about 3 hours total.

I didn't see it anywhere in the thread, but I plugged in the GMT800 ABS wiring and it had the exact same plug as the 400. I'm not 100% sure that the signals are the same, but I've got about 200 miles since I swapped them and the ABS light hasn't come on. And when I slam the brakes the ABS works as it should.

 

[Big T]

I just finished up my swap last weekend and it really is night and day different. The swap really wasn't bad at all. For me the biggest time consumer was swapping out the upper ball joint. Those damn rivets were a pain... I changed out both upper and lower ball joints, used the 409ES outer tie rods and had about 10 hours in the swap over two days. Some of that time was power washing/painting the new spindles, and a good 3-4 hours was messing with the upper ball joints on both sides. If I were just straight swapping the spindles, it should have taken about 3 hours total.

I didn't see it anywhere in the thread, but I plugged in the GMT800 ABS wiring and it had the exact same plug as the 400. I'm not 100% sure that the signals are the same, but I've got about 200 miles since I swapped them and the ABS light hasn't come on. And when I slam the brakes the ABS works as it should.

Great to hear of another success.

It took me quite a few hours just to do the reaming. Then again I was doing two trucks at once.

Upper ball joints had been done previously, but yes the rivets are a PITA. Same with the rivets for the ball joints on the stamped steel LCAs, but those too had been done previously.

My ABS has never worked and I have not been able to solve the problem. The brakes themselves work great. Like you said, night and day difference. Up next is the GMT 800 Corporate 14 FF axle with disc brakes for my son's '94.

 

[ak diesel driver]

don't want to go back and read 5 pages did you use the gmt400 control arms and simply reream the ball joint holes?

 

[ryeguy2006a]

Yes, use your stock control arms and ball joints, but ream out the GMT800 spindles/kunckles to the GMT400 size. Although I wouldn't say simply reream as it is quite a challenge.

 

[Big T]

Yes, use your stock control arms and ball joints, but ream out the GMT800 spindles/kunckles to the GMT400 size. Although I wouldn't say simply reream as it is quite a challenge.

Absent removing the damn rivets holding ball joints to control arms, reaming the knuckles was the most difficult and time consuming part of the job. I did two trucks at once. One got the adapter/tie rod with no reaming and the other I did the reaming. As I recall the lower ball joint hole on the knuckle required an angle drill to ream it.

 

[Turbo6]

So just trying to clarify this. I need 99-06 style knuckles. To do the swap do I need to change out upper or lower balls joint. But still able to keep my tie rods. I've already done the 2500 2wd 6 lug rear. But going to be swapping axles and drums to make for an easier swap out back. Also can you change out the lower arms from stamped to solids. Or is something different on the chassis? I have a 1999 OBS Suburban. Thank you

 

[ak diesel driver]

Are there any other gmt800 brake options we should be looking for?

 

[THEFERMANATOR]

So just trying to clarify this. I need 99-06 style knuckles. To do the swap do I need to change out upper or lower balls joint. But still able to keep my tie rods. I've already done the 2500 2wd 6 lug rear. But going to be swapping axles and drums to make for an easier swap out back. Also can you change out the lower arms from stamped to solids. Or is something different on the chassis? I have a 1999 OBS Suburban. Thank you

FYI, there were differences between the 99/00 gmt800 8 lug spindles and the 01-06. It has to do with the toe rod ends.

 

[Big T]

So just trying to clarify this. I need 99-06 style knuckles. To do the swap do I need to change out upper or lower balls joint. But still able to keep my tie rods. I've already done the 2500 2wd 6 lug rear. But going to be swapping axles and drums to make for an easier swap out back. Also can you change out the lower arms from stamped to solids. Or is something different on the chassis? I have a 1999 OBS Suburban. Thank you

Changing out the lower control arms from stamped/welded steel to forged is on my to do list. I anticipate have to cut off the stamped steel LCAs from the torsion because nothing would remove them the last time I was in there doing ball joints. The forged LCA go on and off easily.