GMT400 Poor Man's Alignment Check

[dbrannon79]

Guys, I decided to pull my 95 into the back driveway and check and adjust if needed for a quick and dirty alignment job today. I have noticed since I had pulled the TT hearing tire tread road noise more so that it had before. looking at my tires I found that both the front tires were cupping on the inside some. reading online I am finding that for some tires this is a normal thing and others say it's alignment or shocks to blame. I figured I would double check and see if anything was going on.

Since I mostly do my own alignment jobs and seem to have had decent luck with it, I would do it again just to ease my mind. I leveled the truck as best I could with my driveway all uneven and cracking. found spots for the two front tires that my torpedo level is almost dead on going my the center of the radiator support, bed floor, and bed side rails. measured the camber on both front wheels placing the level on the rim's flat area below the bead up and down check both front and back of the front wheels. I found that both fronts needed to be pulled outward as they were leaning in towards the truck slightly. Got that done with keeping the same caster angle by moving both the front and back UCA adjustments the same amounts.

after that was done I rolled the truck back and placed two pieces of old floor tile with grease in between like a sammich to give the fronts wiggle room for adjusting the toe.
when I adjust the toe I normally set two jack stands forward of the front wheels and tie a long kite string to one wrapping back around the rear wheels and up to the other front to the second jack stand, pull it tight along with using a twig between the string and tire at the far rear giving a space so it's not touching the sidewall. Then use the rear rims to measure the distance front to back of the rim adjusting the stands closer or farther away to get the strings a straight and in line with the truck as possible. as long as the wind isn't blowing too much I can get it perfectly straight.

Then I move to the front wheels and use the rims to measure front to back of each wheel, taking the difference giving me my toe in/out measurement. also making sure the steering wheel is straight with the wheels. I did all this and I'm now perfectly straight with a 1/16" toe in.

something I ran into which the truck has been like this from the day I purchased it is the rear axle is off set to the drivers side by almost 1 inch. you can see this in the distance of the string on the passenger tire comparing to the drivers side. not sure if this can cause an issue or how I would go about fixing it if I need to.

 

[dbrannon79]

You can see my level sitting on the radiator support. Using this method I am sure that if my rear axle is not straight it's all gonna be off since I am using it as the reference point instead of the frame. I guess I can measure the distance of the back edge of the frame to the axle tube and see if that is straight. curious though if this can be an issue even if it's straight but shifted over to the left.

 

[JayTheCPA]

Definitely neat and nearly no expense, but still looks like a bit too much work for me

I went this route:

DIY Toe Alignment Tool

TMR Customs stocks the tools to get your off-road project finished! Check out the DIY Toe Alignment tool and save the cost of an alignment after a rough off-road use!

www.tmrcustoms.com

Have to admit that I had the local shop actually use the TMR tool on my beastie, but it worked well. For fun, I bought two of the exact same tape measures just to minimize any difference in actual measurement between the two.

Not sure about the GMT400, but my SOB dually likes 1/8" toe-in.


Bonus is that if the steering is not centered, the TMR tool can also help with re-centering. But this requires jacking the front, pulling the tires, and remounting the tool for each tweak while dialing-in the steering. Or, can do like my shop did of simply pulling off the steering wheel and re-clocking it.

 

[dbrannon79]

I’ve seen these tow plates. Would probably work better than my string method but for me it’s a chore to pull the wheels off with a breaker bar and reinstall. I had wanted to rotate the tires but was already too wore out for the day lol

I’ll just make an appointment for discount tire to rotate and balance them not sure if there open tomorrow. Then again I’m cringing just thinking about it. When they installed the rims later when o tried to pull one off the back I found out they somehow fubared every one of the lugs and studs on the rear axle. I had to replace everything. They must have spun them on with an impact or over tightened them. Just glad I didn’t find that out while I was on the side of the road trying to use a spare!!

 

[dbrannon79]

I did craw under the back and measure the ends of the frame rail to the axle tube and it’s almost an 1/8” off so I’m assuming spring hanger bushings are sloppy. Measured the distance between the leaf springs to the string just forward of the back wheels and that’s the same on both sides. Not sure if the axle can be shifted over though since the U-bolt brackets are welded to the axle. I’m sure the whole axle with spring are shifted at the hangers due to bushings or something.

 

[dbrannon79]

Took it out on the road (getting ready for fireworks tonight for my two boys). All that work and it drives the same as before I touched it. Tread road noise, has a slight wandering as it wants to follow and ruts. I’m thinking this is all due to the tire cupping in the front along with running 265/75 Pathfinder all terrain tires instead of the factory size highway tires.

Hopefully after I get them rotated some of that will to away.

 

[dbrannon79]

I never posted an update on this... last week I attempted to stop by discount tire to have the tires re-balanced and rotated. well that was a not no but hell no LOL there were so many vehicles in the parking lot I could not even park to go in and inquire. went back home and conned my two boys to help me rotate them... rotated the rears forward and flipped the fronts to the back on opposite sides so they would hopefully wear into the cupped areas and smooth out. I've been driving it and that seems to have put a stop to the wandering with the ruts of the roads. she drives straight but still has a little slop in the steering wheel. I did find that the joint on my pitman arm has a very slight movement in it along with the center link will move up and down when applying pressure on the steering. that can only be the idler arm again. I've gone through 4 or 5 of them already, each one with the same problem.

They no longer make the HD ones made for RV chassis so I don't know what to do there. If only there was a way to eliminate the inner tie rod ends making the center link a solid bar between the outer tie rods similar to how a straight axle 4x4 is or iirc some mid 90's dodge trucks are. I think the steering design GM did on these (same design as the 80's GM cars) are just weak in this area.

 

[MrMarty51]

Mount two arms about a 1/4” apart. Weld them to a piece of flat and drill a hole through both near the top, away from the plate.
Make a pointed piece of steel 1/4” thick and drill a same size hole through it.
You are building a teeter totter affair. Hole through the non pointed end, a relatively tough spring through that hole and make another loop from a washer, single chain link, etc and hook other end of spring to that.
Jack front of truck off ground.
Put the pointy end of the steel against the tire with spring pressure, holding the flat plate to the floor so it dont move.
Rotate tire to scribe a line all the way around it. Do the same to the next tire.
Lower vehicle then measure distance between scribe marks at back of tire.
Measure distance between scribe marks at front of tire.
The difference between measurements will be the toe in/toe out, so, now start adjusting.

 

[MrMarty51]

Here is a similar version of what I was trying to describe.

And here is another version.

Shove the point against the tire, it dont have to be in the middle and both front tires do not have to be scribed exactly in the same position. Just make the scribe deep and plain enough to be seen.
Might also do an internet search for tire scribe.
With one of these devices it matters not if the bolt pattern is a small four, metric, american, six or eight. Just scribe and measure.
Oh yeah, also, there are measuring sticks on legs with 1/32nd inch marks to make this a one man operation. Otherwise it will be a two person operation for a partner to hold one end of a tape measure while you, or another measures.

 

[MrMarty51]

Similar to this.


Slide it from back to front, front to back to get the measurement between scribe marks.

 

[dbrannon79]

I have done this before for getting the toe set. not too hard to do. my main issue is with the idler arm on the frame opposite of the gear box. seems to always get sloppy at teh pivot point. I've gone through 4 or 5 delco units now over the last couple of years.

Supersteer used to make this one but stopped production on them. it was the go to for this exact problem I have been having.

Part number is SS170

 

[dbrannon79]

These units from SS use tapered roller bearings like a wheel spindle does which stops all play. the OE units use a couple of bushings to hold the shaft for the arm. after a few hundred miles the bushings wear in and allow the arm to move up and down along with the center link causing the toe to never be correct. I can set my tow then drive and re-check and it will always be different.

when I jack the front wheels off the ground I can grab ether tire (passenger side more so) and wiggle back n fourth seeing my center link move up and down with this arm moving at the shaft on the frame.

I have pondered about fabbing up a bracket so I can possibly use the SS175 made for the GMT800 trucks.

Here is the SS175 mounted in the OE bracket on an 99-03 truck. only thing I need to find out is if the taper shaft is the same as the GMT400's
Instead of the GMT400 using three bolts through the frame, the frame has a bracket welded to it which has two bolt holes to hold this in place.

I'm sure I could use a couple pieces of 2" x 4" angle, drill the holes for it and to mount on the frame, then it would accept the GMT800 idler arms

 

[dbrannon79]

I reached out to Super Steer to see if they would provide the measurements on the taper shaft of both the SS170 (discontinued) and SS175.

I might have to venture out to the pick a part yard and get this part from a NBS truck so I see if it will work and possibly fabricate some bolt on brackets.

 

[dbrannon79]

Here is a link to the thread where I dissected one of these idler arm brackets and attempted to modify it. it worked for a couple months till it started getting sloppy again. replaced it with another AC Delco unit until now... again sloppy.

GMT400 Idler Arm Bracket

Good morning. as you probably have already heard, the heavy duty idler arm bracket with shaft that SuperSteer made is now discontinued. part number SS170. My truck has been eating these factory designed idler arms for dinner. Replaced 4 of them over a span of 2-3 years now. Currently I...

www.thetruckstop.us

 

[MrMarty51]

Here is the tire scribing device, cut pieces of scrap and weleded it all together, about a half hour.