Dog tracking and throttle steer

[440racer]

This is my first post so please bear with me.

Also, this may should be in suspension forum but I'm not sure.

I now am the 4th generation family owner of a 65 c10 I purchased from my father-in-law.

The truck was in a bad front end collision and repaired before I bought it.

When I got the truck it had a crate 350 with TH400 transmission, manual steering and brakes.

I had a 1985 front suspension (cross member down) installed to add disc brakes and power steering.

Since then I have replace the spindles with drop spindles, new factory spec front coil springs, new DJM upper control arms, new power steering box and idler arms on front and Capt fab steering box plate.

The only modification to the rear is 1969 Chevelle coils springs (all specs are the same as stock but spring rate is lower) this creates a little drop in the rear and a smoother ride with an empty bed.

****My first problem is that the truck dog tracks down the road with the rear tires rolling a couple of inches to the right of the front.

I have used a plumb bob to check squareness of the frame and none of the measurements are more than 1/4" different. However, this is the first time I've ever tried this so the results may not be perfectly accurate.

****The second problem is that the truck veers to the left under acceleration and then veers back to the right when lifting the throttle. It brakes straight so the veering is not related to the brakes I don't think.

I had the front aligned by an "old school" guy that has been doing alignments for 50 years and was very highly recommended. The truck rides down the road straight with the exception of throttle changes and he said the rear trailing arm bushings were good with no play.

Any help/advise is welcome.

[chevy_mike]

First, welcome to the forum!!!!

Have you measured the wheelbase on each side? Center of the front spindles (with the tires straight ahead) to the center of the rear axles. Both sides should match within an 1/8" If not, something is not square and would cause the dog legging. This dog legging will also cause the on/off throttle veering.

Just because the front end is aligned, does not mean front to rear is square.

[440racer]

Thanks for the welcome.

Great idea on the wheelbase. I haven't checked that and I now see how that could also create the throttle steering.

I'll check this weekend and post results.

Thanks again.

Originally Posted by chevy_mike

First, welcome to the forum!!!!

Have you measured the wheelbase on each side? Center of the front spindles (with the tires straight ahead) to the center of the rear axles. Both sides should match within an 1/8" If not, something is not square and would cause the dog legging. This dog legging will also cause the on/off throttle veering.

Just because the front end is aligned, does not mean front to rear is square.

[BR3W CITY]

I'd suggest lifting the truck up and seeing what kinda condition your trailing arms are. They can erode, the center of the stamped pieces can "Split" like old lumber.....yet remarkably still hold together. The more destroyed they are, they can allow flex and sway. You'll see some of the high performance guys stitch weld them to stiffen them up, box them, or replace them with tubular or fab unit (or just repro's).

Also, if your truck has the 85 front stuff with power steering, the pump will be spaced off the drivers frame rail anywhere from 1/8-3/4 of an inch because the frame wasn't setup for it originally. This will result in your steering usually going 1/4-1/2 turn LESS to one side...this isn't a huge problem for most vehicles, but the uneven center point can really screw with someone setting up the tierods and center link if they aren't aware of it from the get go.

I'd also suggest (as the others have mentioned) taking the truck to a higher-end suspension or alignment place that has the capability of taking the alignment in 3d space. "old school" alignments, and front-only alignments won't track ALL the axis on both sets of wheels; basically, you can be plumb/square from one observed measurement, way off on another in relation to it.

Most of the time the simple alignment is all you really need after a lowering, or to touch things up after potholes or something....but when you compound 50 years of history, at least one larger incident, lowering, and who knows what other repairs or changes over the years...its worth the money to know for sure. You'll be eating tires, and all around dangerous if your tracking poorly at highway speeds.

[68racer]

You need an adjustable panhard rod on the rear. When you lowered it the axle moved to the right. This can be corrected with the new one.

[440racer]

Great suggestions BR3W City an 68racer.

I will check the trailing arms in detail.

You are correct about the steering box location and it's effect on centering. I had noticed the lack of right turn and increased left turn. The alignment guy explained the steering box offset is the cause and the reinforcing plate adds to the issue.

I will find a alignment shop capable of checking all axis.

I will also be looking for an adjustable pan hard rod. That is something I considered as a possibility.