• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

GMT-400 to GMT-800 brake conversion tie rod discussion

Big T

Big T

Well-Known Member
Messages
11,897
Reaction score
26,290
Location
Fullerton, CA
Ferm, could you use that solid adjusting sleeve for the GMT-800 brake conversion by purchasing one to fit the smaller GMT-800 tie rod thread and drilling and tapping the other side for the larger GMT-400 tie rod?
 
I'm sure you could get something made to work. Not sure how well they would work for the swap though as gmt-800 outers use a female thread, and gmt-400 uses a male threaded tie rod end.
 
THEFERMANATOR said:
I'm sure you could get something made to work. Not sure how well they would work for the swap though as gmt-800 outers use a female thread, and gmt-400 uses a male threaded tie rod end.
Click to expand...

It's a matter of what's cheaper: 1) having the mods done at the sleeve so that the threaded rod to the GMT-800 tie rod is uniform, or 2) modifying the cut-off piece of GMT-400 tie rod to fit the GMT-800 tie rod female end and the sleeve.
 
Big T said:
It's a matter of what's cheaper: 1) having the mods done at the sleeve so that the threaded rod to the GMT-800 tie rod is uniform, or 2) modifying the cut-off piece of GMT-400 tie rod to fit the GMT-800 tie rod female end and the sleeve.
Click to expand...

The challenges are the rod/thread size difference & one side of the adjuster sleeve needs reverse threads. Guess you could get a blank hex billet & drill each end the different size to make your own sleeve, but then you need to reverse thread one side. Then cut the inner GMT800 tie rod & thread the end of that shaft.

I had a set of billet aluminum adjuster sleeves traded to me for powder coating services, but like the steel versions Ferm used better for durability.

I have wondered about how similar the GMT800 center link geometry is to GMT400. The pitman arm is quite similar if not exactly the same geometry - looks a bit heavier built. The Rare Parts heavy duty versions of the GMT800 are available & look stronger, but that gets into considerable additional $ - haven't heard enough reports to know if or how much more durable they actually are though.
20160115_114622.jpg
 
Why again can't you use the GMT-400 outer tie rod end with the GMT-800 knuckle? Was the taper different? Or was it the offset that was different? Might be better off to find a tie rod end that uses the same thread as the GMT-400's, but will fit the GMT-800 knuckle. Since the tie rods of the GMT-400 trucks uses the 11/16X18 thread, there is ALOT of tie rod options since this same thread was used in so many GM cars like the CAMARO and several other full size muscle cars. The solid sleeves I used were not listed to fit the GMT-400 trucks, but instead for numerous early muscle cars. Just so happens they were the same dimensions, so they work. Might be able to find a tie rod end for an early full size car to take care of this issue instead of the adapter.
 
The tie-rod hole/taper in the GMT800 knuckle is bigger - from a rough quick measurement: 9/16 -> 11/16" As compared to the GMT400 tie-rod's 1/2 -> 5/8"

I spent some time looking online looking last winter, but maybe should look more. Need to find a Moog or other table showing all the outer tie-rod ends with 11/16-18 threads.

Suppose there might be taper bushings as I know some dirt track racers adapt various steering component's that way. But finding an already engineering, mfg'd, & time proven tie-rod end would be better than this adaptor that goes down to M14 diameter (had a co-worker turn mine down at work), but that cut, plus threading does make things weaker than a full 11/16" forged tie-rod end shaft.20160115_134740.jpg
 
THEFERMANATOR said:
Why again can't you use the GMT-400 outer tie rod end with the GMT-800 knuckle? Was the taper different? Or was it the offset that was different? Might be better off to find a tie rod end that uses the same thread as the GMT-400's, but will fit the GMT-800 knuckle. Since the tie rods of the GMT-400 trucks uses the 11/16X18 thread, there is ALOT of tie rod options since this same thread was used in so many GM cars like the CAMARO and several other full size muscle cars. The solid sleeves I used were not listed to fit the GMT-400 trucks, but instead for numerous early muscle cars. Just so happens they were the same dimensions, so they work. Might be able to find a tie rod end for an early full size car to take care of this issue instead of the adapter.
Click to expand...

That would be great if one of you pros could find a tie rod end that worked to eliminate the machining on this portion of the GMT-800 brake conversion. The last part would be the reaming out of the spindle/knuckle to accept the ball joints and that I can do.
 
I'll definitely do some more looking as eliminating the adaptor with a ready-made tie-rod end would be better. On Monday, I'll call the customer service line from that website with Moog database.

I intend to use the GMT800 forged lower control arm & the matching Moog balljoint. I don't see any dimensional differences in the lower arm, with the geometry of my '95's stamped/welded steel lower arm - but will wait to confirm it works when I have the GMT800 arms in place. I've got the reamer to do the top taper in the knuckle to match GMT400 upper ball joint.
 
It looks like there is 2 choices for an outer tie rod end for the GMT-800 swaps. One is .68" shorter, and the other is .62" shorter. The 1st option is an ES409R. It is 6.75" long, uses the 11/16X18R thread, and appears to use the same taper angle from what I can find as the GMT-800's, the primary difference is it uses a 9/16" instead of 14MM stud. The other option is an ES2218R. It is 6.81" long, also uses the same .687X18R thread, also uses what appears to be the same taper, and a 9/16" stud instead of a 14MM. The primary difference between the two is the length of the taper/stud. The ES2218R uses a 1.27" long tapered portion, and the ES409R is .66" long. I have only been able to find limited dimensions for the newer tie rod ends, so this is as far as I got with it. Provided the tie rod to knuckle orientation is similiar between the GMT-400 to 800, the 3/4" shorter tie rod shouldn't be much of an issue as I had about 1.5" of thread into my sleeves on each tier rod end when I did mine, so 3/8" less should be a non issue. Just need to find the correct taper length, and should be golden.
 
SmithvilleD said:
I'll definitely do some more looking as eliminating the adaptor with a ready-made tie-rod end would be better. On Monday, I'll call the customer service line from that website with Moog database.

I intend to use the GMT800 forged lower control arm & the matching Moog balljoint. I don't see any dimensional differences in the lower arm, with the geometry of my '95's stamped/welded steel lower arm - but will wait to confirm it works when I have the GMT800 arms in place. I've got the reamer to do the top taper in the knuckle to match GMT400 upper ball joint.
Click to expand...

I hope your not offended by this request, but can I get sloppy seconds on your reamer? I mean, I'll pay you a rental fee to use your reamer. Nothing urgent. Just planning out this project.
 
Thanks much Ferm!

Both the GMT400 & GMT800 knuckle's tie-rod pad measures around 1.31" thick, so the second one with the 1.27" long taper may work if the big/little diameters & taper (don't know if tie-rods are commonly 10 degrees?) are right.

Too tired tonight, but tomorrow, I'll see if ES2218R has the right taper & report back.
 
I think I've got a solution - still needs to be bolted on the truck & aligned to confirm. Tie rod combination measures right.

So got the O'Reilly store brand ES409R to mock up & see if it could work. The taper didn't fit the GMT800 knuckle as is. I had an Allstar Performance 9.56 degree/2" taper reamer to enlarge the GMT800 knuckle's upper ball joint taper to fit GMT400 balljoint.

So in addition to reaming upper balljoint hole, I reamed the GMT800's tie rod hole to fit the ES409R tie rod. It fits tight.

I'm not certain if this tie-rod is 10 degree or 7 degree taper? Not easy to discern that 3 degree difference. May do the math on big/small diameters & see which it comes out to.

Dirt track racer friends tell me it won't matter as a mismatch 7 to 10 degree taper interference fits tight regardless? Anyone have experience with this?

The tie rod stud has a castle nut/cotter pin, so have same safety backup as stock setup.

20160116_161438.jpg
 

Attachments

  • 20160116_161404.jpg
    20160116_161404.jpg
    107.7 KB · Views: 30
SmithvilleD said:
I think I've got a solution - still needs to be bolted on the truck & aligned to confirm. Tie rod combination measures right.

So got the O'Reilly store brand ES409R to mock up & see if it could work. The taper didn't fit the GMT800 knuckle as is. I had an Allstar Performance 9.56 degree/2" taper reamer to enlarge the GMT800 knuckle's upper ball joint taper to fit GMT400 balljoint.

So in addition to reaming upper balljoint hole, I reamed the GMT800's tie rod hole to fit the ES409R tie rod. It fits tight.

I'm not certain if this tie-rod is 10 degree or 7 degree taper? Not easy to discern that 3 degree difference. May do the math on big/small diameters & see which it comes out to.

Dirt track racer friends tell me it won't matter as a mismatch 7 to 10 degree taper interference fits tight regardless? Anyone have experience with this?

The tie rod stud has a castle nut/cotter pin, so have same safety backup as stock setup.

View attachment 46924
Click to expand...

Yay! Parts listing please, using Moog's Stuff and the part # for that adjusting collar. Now we're getting much closer.
 
The Moog number for the tie rod end I got with be the same ES409R. My weekend days off work are Fri/Sat, so I'm done for now, but will get back at it again next weekend.

The aluminum adjusters in the pic are from ProForged and believe the part # was listed for my '95 K2500 - search Summit Racing's site if you want these adj sleeves. I'll have to see what I think when everything is assembled. I do like the idea of a solid steel part there instead of Al.
 
I haven't mis matched automotive taper joints and don't know the real world tolerances but I would think you would want them pretty tight. Even 2 degrees included taper mismatch seems like a lot. Isn't that what keeps the stud from turning the close locking taper. Its the close taper that makes the stud a "short stud" or short cantilever. A slight mismatch as long as the taper in the male was faster would still hold tight from draw pull of the nut. It would create a releasing taper but would hold tight as long as the pull kept the taper locked. But it would not be quite as strong and have a smaller contact area. You would go from a plane contact to a line contact theoretically. Real world if angles were close it would distort and get a wide line contact. It may wear faster and may "woller" out the female taper???.

I think a faster taper would hold tight and be as good as say a heim joint or better but again wouldn't be as good as a locking taper fit.

What say you guys that have seen worn tapers ??? Last time I did tie rod joint ends you couldn't tell any wear at all since they were locking tapers. I have seen old lathes and drill presses with thousands of in ands outs of locking tapers and they still fit locking tight. I have never seen how a mis match tapers wears out ?????
 
Not sure how many degree's out you can be, but my neighbor has a MF tractor that peels the nut off due to wear. His son is a shop teacher and built a bushing to my measurements and I welded it in place. This spring will tell if it works.
 
That's my question/concern also. I've more often heard my dirt track racer friends talk about a tie rod reamer being 7 degrees. I will do more checking this coming week.
 
NVW said:
Not sure how many degree's out you can be, but my neighbor has a MF tractor that peels the nut off due to wear. His son is a shop teacher and built a bushing to my measurements and I welded it in place. This spring will tell if it works.
Click to expand...

I know they make ready made mismatch bushings that racers sometimes use.

We had an IH 706 top of the spindle nut that held the tie rod down, that finally wore (tractor had ~ 17,000 hours - not a typo) to where you couldn't keep the nut tight. After we'd had enough of it loosening up, we just pulled the nut off, & ran a good hot penetrating bead around the top of the shaft & tie-rod. Still tight now, but tractors don't go down the road at 70 mph :)
 
You must log in or register to reply here.
Back
Top