Technical HELP, car acts squirrelly when stomping throttle. Not good things. Something is wrong.

This may or may not be your issue. Way to many years ago I had an OT car that I swapped in a 4 speed and took out the AT. Every thing was fine as long as I drove normally. When I stood on it, it would take up 3 lanes and had a severe shake. I forget what happened, but I installed a different 4 speed. I tore the first one down and found that one of the internal shafts was slightly bent. With the 2nd transmission there was no lane changing at all under full throttle. The lesson I learned was to never buy a trans out of a wrecked car.

Hope this might help.

Len

 

Well, this is an old thread, but I hate reading stuff like this and not seeing an answer. QUICK UPDATE:

1. Thank you to all of those that have made suggestions. MUCH appreciated!

2. 24riverview, yes upon closer inspection, the car was tearing the right front leaf spring perch off.

3. I did check the rear axles to make sure they weren't rotating in the housing. No sign of that...

4. Can't imagine any problem coming from the transmission as it is a new Tremec TKO600.

So now, I have made a BUNCH of changes (I know, not the best way to diagnose, but I am getting tired of this...) First of all, I welded up the cracks and fully boxed the front spring mounts. Then I swapped the old 8.5 10 bolt 4.88 rear end for a rebuilt 12 bolt posi with 4.56 gears and a new pair of heavier leaf springs. The axle housings are fully welded to the center. I switched out the McGaughy traction bars for a set of Caltracs with aluminum front bushings. New drum brake components and new 50/50 shocks were added. EVERYTHING is new back there now.

Haven't set the pinion and run the brake lines yet, but as soon as I do, I will go for a drive and report back. If it still does it, it almost HAS to be narrowed down to the front suspension or the frame.

Stay tuned!

 

Appreciate the update, still curious what it ends up being, hopefully the boxed spring mount and the stiffer leafs get it sorted. Lots of power makes all sorts of things act strange.

 

curious, did you carefully inspect the rear spring perches and the locating bolt on the spring? I had a similar problem with my 55 years ago, I let the U bolts get loose, and one of the perches got wallered out.

 

Squirrel...

Yea. The other springs were perfect when pulled out. No issues that could be seen.

The rear spring perches were new before with new poly bushings. I pulled them apart, painted and lubed everything appropriately before putting it back together. Anxious to get it off the lift and back on the ground.

Freaked a little when I looked at the date of my first post on this thread. I am losing good car time! Hope to provide an update soon.

 

Assuming you've checked & eliminated all the previous possibilities, then what about...
Tire pressure?
Driveshaft U-joints?

 

Just wondering if the weight transfers to the opposing side as the air bleeds down from one shock to the other. The air transfers to the other side. All the lines should run back to a solenoids that are controlled by pressure sensors. The computer maintains the preset pressure selected and won't allow air to transfer fro side to side.
Alternatively the saddle on the housing may not be aligned with leaf spring, I had a car years ago that did similar under load and the entire car squirmed. I eventually established that the hole in the differential saddle was larger that the centrebolt on the leaf spring causing movement under acceleration due to movement. Support the rear of the car on stands and loosen the U-bolts and check this. It's a PITA and takes time, might be the solution; it could be that the front spring eye may have failed or a leaf has cracked?

 

My first thought when I read the thread title was...Better check the engine mounts. Sounds like you've checked everything by now.

 

The fact that the car squats in the rear in a highly unusual manner can only in my opinion point to the rear of the car,( frame flex , one side of the axle not providing torque reaction etc.)

 

Yep. Tires are good condition and properly and equally aired. The driveshaft was custom built for the car by an experienced shop. U-joints have been inspected, replaced anyway, and are properly phased and greased.

Nutty, eh?

 

I have most suspected the previous posi. Was thinking it was dragging on the left side and pulling on the right... causing it to turn like a Bobcat...

When I opened the case, everything still looked very good, so not sure about that...

Anxious to get the little things tidied up and see if the replacement rear did the trick.

If not, I'll move forward in the car.

Thank you so much everyone for your comments. Very very appreciated.