GMT 800 Brake Conversion > Silverado HD 2500

[Grisley1958]

I remember on the video the guy said 27" worked perfectly

 

[DieselAmateur]

I saw that too @Big T, think the 24" may be the hose length excluding fittings and your 26" length end to end may be one and the same.

The offroad design link for stainless brake lines is listed as 25", may be the magic 27" length if that doesn't include the ends

 

[Grisley1958]

Okay, I got my parts from rockauto today and went through the boxes to make sure everything was in there. I grabbed one of the tie rod ends to check the fit in the spindle and it only sticks through about two threads even after a tap with a dead blow mallet to make sure it was seated. Looks like they will need a little reaming to work. I was also surprised at how much smaller the upper ball joint size is in the 2500HD spindle compared to the size of the ones in the GMT400. Lots bigger brakes but smaller ball joints and tie rod ends. Makes me scratch my head!

 

[DieselAmateur]

Can you post a picture of the tie rod end and spindle? Any idea what size reamer is needed?

Waiting to hear what the other folks who have done this conversion have to say about the tie rod end.

Does seem strange that the front end of the 800s used smaller ball joints. For folks with forged lower control arms on the 400 chassis I can see reaming out the knuckles and keeping larger ball joints instead of swapping LCAs.

 

[Grisley1958]

Problem with using the old LCAs is the turning radius is cut down because of the stamped LCA. (At least that's what I hear)
I have a 7 degree taper that seems like a good fit for reaming the tie rod but doesn't fit the ball joint holes. I have a 10 degree coming tomorrow that should fit that

 

[DieselAmateur]

Yes, read in other threads that turning radius with stamped LCAs is not as good as forged. But with forged LCAs (which I think were first on 96 trucks and after, hence my '95 having stamped ones) there apparently isn't the same turning radius issue.

Mentioned here in this thread, but apparently you need that 7 degree taper in addition to the 10 degree. 7 degree is upper taper and 10 degree is lower taper see post #163. I've never heard of anyone needing to ream for tie rod end when using the 409 tie rod. Did you get your knuckles from a wrecker yard or order new? Just for fun how does the stock tie rod fit? Remember there's the rare 99-00 knuckle that will fit the GMT400 spindle, maybe you got one of those by chance?

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

Which holes are reamed 7 degrees and which are reamed 10*?

www.thetruckstop.us

 

[Grisley1958]

the 7 degree taper seems way off for the upper ball join but fits the tie rod hole. I'll confirm the fit of the 10 degree when I get it. I haven't tried the original yet but the new Moog ES409 doesn't stick through enough as is. My used parts were from a 2001 2500HD

 

[DieselAmateur]

@Big T can you confirm where and which reamers are used on the GMT800 knuckle?

 

[Big T]

Problem with using the old LCAs is the turning radius is cut down because of the stamped LCA. (At least that's what I hear)
I have a 7 degree taper that seems like a good fit for reaming the tie rod but doesn't fit the ball joint holes. I have a 10 degree coming tomorrow that should fit that

This ^^^ is true. Stamped steel turning radius is 4’ greater than the forged. I have a long overdue project to install forged LCAs on my son’s ‘94 Suburban for this reason. Depending on how things go, I may get this done in the next 3 weeks. Just can’t afford to have the vehicle down. If I can get the shift cables replaced on my 5 spd manual Honda Accord, then I can address the LCA change. I’m also installing a new AC Delco reman IP on his Suburban.

I fully expect that I will need to cut the stamped steel LCAs off the torsion bars. I was unable to remove them the last time I did the lower bushings and had to remove the cross member, torsion bars and LCAs as a complete unit.

 

[Big T]

@Big T can you confirm where and which reamers are used on the GMT800 knuckle?

I’d have to go back to the thread to determine which went where, but it was a 7 and a 10 degree ream, probably the 10 for the ball joints and 7 for the tie rod. Sorry I don’t have a photographic memory on this.

I may have to do the reaming on the ‘99 as it used the tie rod adaptors which had play in the threads of the GMT 800 tie rod ends and that caused wear problem in the UCA bushings. I reamed the knuckles on my son’s ‘94 to take the other tie rod.

https://youtube.com/shorts/dYPYrs2KvPM?feature=share https://youtube.com/shorts/C2Bqn2gPRZA?feature=share

 

[Grisley1958]

I had the day off today and my 10 degree taper showed up so up to the shop to see how it fits. Taper seems to be right on. Couldn't fit the knuckles in my drill press (not tall enough) so I mounted it in my 3 legged Harbor freight vise to try it out. Went on slow speed really carefully and kept checking fit. When you get to the point where the threads of the ball joint will just come through the hole, you're almost there. I went until I could screw on the nut by hand and see half the hole through the castle. wound up using the 10 degree on the tie rods too. Original tie rods are really loose in the knuckles (not what I had read somewhere) but the ball joint holes are smaller. Probably the ball joint itself is at least as large as the GMT400, maybe it's just the taper that's smaller. I literally had both upper holes and both tie rod holes done in 20 minutes. The "Speedway" taper I got went through that cast like butter. Now I have to replace the ball joints and bushings in the lower control arms and then I can install everything! I'll probably burn out the old bushings.

 

[Big T]

I had the day off today and my 10 degree taper showed up so up to the shop to see how it fits. Taper seems to be right on. Couldn't fit the knuckles in my drill press (not tall enough) so I mounted it in my 3 legged Harbor freight vise to try it out. Went on slow speed really carefully and kept checking fit. When you get to the point where the threads of the ball joint will just come through the hole, you're almost there. I went until I could screw on the nut by hand and see half the hole through the castle. wound up using the 10 degree on the tie rods too. Original tie rods are really loose in the knuckles (not what I had read somewhere) but the ball joint holes are smaller. Probably the ball joint itself is at least as large as the GMT400, maybe it's just the taper that's smaller. I literally had both upper holes and both tie rod holes done in 20 minutes. The "Speedway" taper I got went through that cast like butter. Now I have to replace the ball joints and bushings in the lower control arms and then I can install everything! I'll probably burn out the old bushings.

Burn out the old bushings and install the black urethane bushings.

 

[davo727.b]

Do the 8 lug 1995 2500 4x4 wheel bearings bolt into the gmt800 spindles? My bearings are pretty new. Contemplating doing this mod. Thanks.

 

[Grisley1958]

I'm not sure but I finally have a little time to work on mine today, so I'll check. I think I have a used GMT400 bearing/ hub on my parts shelf.

 

[Grisley1958]

I would have to say yes! I don't see any visible issues. Bolts lined right up and fits the knuckle same S the new one. Depth from back of hub to mounting surface measures the same.

 

[Grisley1958]

I wish I'd known that when I ordered parts! I'm sure a front bearing without a abs sensor is a lot cheaper. Couldn't find one without for the 2500HD.

 

[Big T]

Do the 8 lug 1995 2500 4x4 wheel bearings bolt into the gmt800 spindles? My bearings are pretty new. Contemplating doing this mod. Thanks.

Yes and they all had ABS, so no way around that.

 

[Grisley1958]

Yes and they all had ABS, so no way around that.

1994 and earlier only had rear wheel abs so those should work. I think 95 and up did have sensors in the front.

 

[Grisley1958]

I got the bushings pressed in the GMT800 lower control arms this morning. Pictures show my rigging. They actually pressed fairly easily with the silicone grease. The thick washer on top was to prevent all the pressure from being on the center. Seemed to work pretty well. Bearing race on the bottom was perfect size to press into.

 

[Grisley1958]

Pictures didn't come out in the order taken!