I have a 1975 GMC C15 shortbox with a 454. I built it myself and use it for drag racing only.
It originally had a 350 so I automatically swapped the front springs for springs from a C10 that
had the 454. I have hoosier 30x9 slicks and seem to have good traction off the line witha 2 sec 60' time. Not great but a good start I think.
Mid-track in the 1/8 mile it starts spinning and can get scary. It is stock ride height
and has stock style shocks. I was planning on removing some leafs in the rear leaf spring to help it squat and also add some traction bars. Does this seem like a good idea? What do you recommend?
Also, the front end seems stiff. should I go back to the 350 springs? Oh, and I can't afford getting rid of the leaf springs.
Traction with a pickup?
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I'm wondering exactly what is going on at mid track that is causing it to spin. Does it do it on every pass, or is that a once in a while deal? Is this happening at the 2-3 shift? How much pressure in the slicks? Is it possible you're feeling them walk around due to low pressure instead of spinning?
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Thanks for the interest in my problem.
It isn't just a feeling because you can see it from outside the truck I am told. People tell me I am all over the place (exaggerated a little I am sure). It does happen all the time.
I started tire pressure at 18 and went down to 12. This did help as the times went down. For a while I had a problem with shifting late into second which would break the tires loose. Then I fixed that and I think they start to spin before the 2-3 shift. Not totally sure though. but yes the third gear is spinning them bad. It is strange though that I can have traction from a stop and not while I am moving. Maybe the converter stall is low enough to cause this. I was thinking that the loss of traction was a weight transfer issue. Also, what is the proper burnout for hoosiers? I spin them in first gear only and don't get any smoke.
Oh, I can't forget to add that I took the rear bumper and tailgate off and it was real bad so I put the tailgate back on and then also went down to 12 psi at that time.
It isn't just a feeling because you can see it from outside the truck I am told. People tell me I am all over the place (exaggerated a little I am sure). It does happen all the time.
I started tire pressure at 18 and went down to 12. This did help as the times went down. For a while I had a problem with shifting late into second which would break the tires loose. Then I fixed that and I think they start to spin before the 2-3 shift. Not totally sure though. but yes the third gear is spinning them bad. It is strange though that I can have traction from a stop and not while I am moving. Maybe the converter stall is low enough to cause this. I was thinking that the loss of traction was a weight transfer issue. Also, what is the proper burnout for hoosiers? I spin them in first gear only and don't get any smoke.
Oh, I can't forget to add that I took the rear bumper and tailgate off and it was real bad so I put the tailgate back on and then also went down to 12 psi at that time.
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Agreed, the stiff front springs are probably not helping matters.
You'll probably have better luck putting more heat in the tires. Do your burnout in high gear to generate some wheel speed, just start in 1st if you need to in order to break them loose then 2nd then 3rd quickly before the tires hook up. At that tire speed say 5 or 6000 rpm for a couple seconds should get them good and warm. That might make quite a difference just in getting the tires hot.
Most 3 speed tranny builders tell you to do your burnouts in high gear to avoid sprag damage in the transmission.
You'll probably have better luck putting more heat in the tires. Do your burnout in high gear to generate some wheel speed, just start in 1st if you need to in order to break them loose then 2nd then 3rd quickly before the tires hook up. At that tire speed say 5 or 6000 rpm for a couple seconds should get them good and warm. That might make quite a difference just in getting the tires hot.
Most 3 speed tranny builders tell you to do your burnouts in high gear to avoid sprag damage in the transmission.
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