The issue is that you are having spring wrap/axle wrap up (basically the leaf spring is becoming an S when you accelerate) on the front part of the leaf spring. Extremely common on all Ford vehicles as they positioned the axle in the middle of the spring. On Mopar products the axle was always positioned forward of the middle point in the axle, making the front part of the spring short and the rear part long, from where the axle is located. It is difficult to wrap up a short leaf spring, but the longer it is the easier it is to wrap it up and get wheel hop. Old school trick was to put a bunch leaf spring clamps on the front of the spring, to try and make the front leaves as close to a solid piece as possible, that will limit the spring wrap up and wheel hop. Make sure that you have good shocks, as if you shocks are bad you will wheel hop no matter what. Also make sure that you have your pinion snubber on the top of your 9". If you can set your pinion snubber at 1"-2" from the floor it will also help limit the axle wrap up, you may have to play with the distance as sometimes they can become a pain, if as you are driving they hit the floor constantly. You can definitely get some Cal Trac Bars, or some other type of traction bars, which will not let the spring/axle wrap up. Here is a good video illustrating spring/axle wrap up:
Here are some of the traction bars on the market, they all basically accomplish the same thing:
Good info from 71ProjectJunk (as usual).
As I say, I'm no expert, but I too had this issue on my 71 M code Mach 1. But this was not due to too much power, but worn out 50 year old springs and the fact it was just a "one-wheeler-peeler".
What I did at first was to replace the springs with a set of 4 1/2 leaf Grab-A-Track. The extra 1/2 leaf definitely helped and that is about all I can say good about the GAT's.
Later, I had my axle rebuilt and added a Traction-lock but retained the 3.25:1 ratio. Then I dumped the garbage GAT's and went back to Eaton Detroit Springs and bought a set of Boss 351 springs which are thicker 5160 spring steel at 153 lbs spring rate. Although with a 3.25:1 ratio, it's harder to "lay rubber", I don't have the wrap-up and wheel hop I once had. As far as I'm concerned, this fixed the issue along with adding a 7/8" rear anti-sway bar. To me, traction bars don't do it for me, just for looks alone.
You could look at having a spring specialty shop add a half leaf with clamps and that will help I'm sure.
Much in line with what others have said; Solid/polyurethane front spring eye bushing, extra half leaf, spring clamps (not quite tight), pinion snubber and stop, and a good pair of 50/50 rear shocks. This set up was good for 4600 rpm launches 7000 rpm shifts on 9 inch slicks with a 1972 R code (with mods). It ran consistent 12.70s. Not quick by today's standards but, was considered to be a fast street car in 1978. Chuck
bill 1 101,
All good stuff here, do you have staggered rear shocks ? that was a big part of the equation for me.
I also added sub frame connectors and under-ride traction bars.
Having no wheel hop does not you will have traction, BFG's are for smoke shows, drag radials are for traction.
I understand what is happening, but am not sure about the best way to go about fixing it. Back in the day I bolted a set of traction bars to my mustangs and that seemed to fix it. I really don't want to do that now.
I do not have staggered shocks and have stiffer springs . I think the torque is overpowering the suspension. I am not a welder and was wondering if there was a fix that didn't cost a lot. I hear everyone about the added leaf and keepers, is there anything else?
Get 2 leaf spring clamp kits, and clamp the front of the leaf springs in between the 2 factory clamps that you should have there. Here are some clamp kits from Jegs, the are only $14.19 a pair, you will need two of them one for each side:
Buy JEGS 60883 at JEGS: JEGS Leaf Spring Clamp Kit Locks Leaf Springs Together for Stabilizing. Guaranteed lowest price!
Hopefully your factory pinion snubber is still there, if it is not get one, and try to see if you can get it about 1" to 1 1/2" from the floor by spacing it. This may just be enough to cure you wheel hop issues with little funds involved. You should be able to use a traction bar snubber on the 9" rear end pinion snubber bracket, those come in different lengths from the aftermarket. If they are a little long you can always get a hack saw and chop a bit off them to get the correct height.
Here is a good video on cheap leaf spring mods to get rid of axle wrap and wheel hop, from an old school guy:
bill 1 101
There are 2 ways to go for staggered rear shocks, one is expensive and requires sheet metal and the other is dirt cheap and only requires a trip to the hardware store and salvage yard.
from the salvage yard, you will need to get 2 lower shock mounts from a mustang with staggered shocks.
the competition lower mounts also have the provisions for a rear sway bar (mine came from a 1973 Q car).
Next you get a length of square bar ( 1'' is what I used } and 4 pieces of flat stock for plates ,you will be making a crossmember and be using one of the previously removed lower mounts to fabricate a new upper shock mount that gets cut and welded welded to the square tube stock.
My setup has been on my car for about 5 years with no ill effects what so ever.
One cannot even tell that the crossmember is even there unless you really look for it.
I looked on the net today for the specific instructions but came up empty.
Having staggered rear shocks really helped with my wheel hop.
brand new shocks, tires are 255/45/17 . I have more room so could probably go to 275 tires, pinion snubber is on the body correct? It appears to have about 2 inches travel. I have grab a trac rear leafs. Thanks for all the help
I can't weld but I had traction bars installed. I forget where I got them from, it was 30 or so years ago. I bought them and had a shop weld them in. They replace the lower spring plate. What I liked about these is they are not obvious like the slapper type traction bars and they also eliminate wheel hop when braking.