Hey mate just had a look through your thread here.
Interesting stuff, but as others have said - make sure all the pieces you're using are strong enough to hold up against a 2-stroke motor.
I'm not familiar with the parts you're using, but I dare say that anything that came out of a smaller RC car won't do the job for long.

Maybe start at the beginning and not worry about suspension and diff for now and just try to get 4 wheels and a motor to move, and then let the build evolve.
You say that you don't have money to spend on this project, but it doesn't have to cost a lot.
You've seen my builds, and the only thing I've spent money on really is the radio gear and the wheels, and you have all that already so you're halfway there.

Have a look around the scrapyards and second hand shops for old motors, bits of aluminium, powertools and anything you can pull apart to use bits from.
Places that repair powertools will usually sell you a broken drill or drinder for a couple of bucks.
Most of the time the motor is burnt out but all the gears are ok.

Keep your options open, and try to always have "2 of everything" when homebuilding, as the first attempt usually never works.
3mm aluminium plate is plenty for a chassis if you put some angle bracing along the edges.
It's easy to cut and light.

One thing I do recommend investing in is an assortment of small nuts and bolts.
Saves a lot of time to have them all there in front of you as you need them.

Be patient and expect to fail a couple of times, and you'll get there in the end.
It took me almost a year of tinkering to get something that worked.
And it's still way off being a good car.