I've got a '90 F-250 4x4 w/a 351 and 5 spd trans. I went to a 10.25" full floater from an '89 F-350 but still have the 3.55 ratio. The problem is that I have no traction. It came with some good street tires but they were worthless in the snow. I have since found some 245-75-16 knobbies that are substantially more aggressive. I live on a steep gravel road and had to use 4wd to get home even in the summer. The knobbies helped in that I can use 2wd but I have to put it first and tractor up and even then, will still bounce & spin. Down hill is the same story. 350 lbs and a full tank makes no difference.
The shocks are reasonably good but do I need to go with some killer duty ones to control things? I had an '85 Bronco II that would go anywhere and my old 2wd '73 F250 didn't bounce as bad as this. I bought this truck to combine & replace the other two but am worried about this winter. Suggestions?

 

Does your "new" rear axle have limited slip or is it an open differential?

 

The stiffer 3/4 ton suspension and tires probably contribute to the bouncing. What air pressure are you running in your tires? My tires call for 80 psi max, but I run them at 40 psi when the truck is empty. I could probably go lower than that and you may want to to stop the bouncing.

I doubt different shocks will help you. The stiff springs aren't moving enough with no load (and 350 lbs isn't a load as far as those springs are concerned).

If dropping the tire pressure doesn't do it for you, well that's what 4WD is for. If you have trouble in 4WD it won't be due to bouncing.

 

I would get the f250 springs for sure in those driving conditions. These trucks are pretty heavy anyways and the springs aren't stiff enough for the truck IMO. It should handle better w those. I don't think he has those springs. I'd do that first. They're much stiffer and progressive

 

You can experiment by putting more weight in the bed.

Like others have said. Your springs are probably to stiff when empty.

 

I had a K5 Blazer with 9" lift and and 39.5 Swampers and it wouldn't go up a hard-packed gravel mound in 4-low without struggling due to MINIMAL suspension travel due to stiff springs.

My Cherokees with soft springs could go up in 2-hi.

Softer springs and/or a locker will help. Spring mods can be cheap or free if you can experiment with changing leaves in the pack.

 

It's got the non-locker but both wheels spin fairly evenly so I don't think it'll help much. I did back off the air to 50 psi without a whole lot of difference there either. Loosening up the springs would most likely help but then that defeats the purpose of having a 3/4 ton truck. I hauled 1900 lbs of manure last spring and it worked great but it's not something I'd want to do every day. I was doing the 4x4 thing but getting out and locking the hubs every time is kind of a PITA. I was just checking to see if there was some kind of magic trick I didn't know about but I guess there isn't. Thanks

 

Try dropping your air pressure even more. At least to 40 psi, maybe even 30 empty. 50 psi is over inflated for what little the back end of an empty pickup weighs.

 

What gear ratio was your original rear? I beat a set of 4:11 or 4:33 would stop that spin.

 

Get a few yards of stone dust and spread it on your driveway.

Better traction due to it eventually turning into sandpaper rather than the marbles you drive up now!

 

Nice, thats the first time I heard that, good one

 

If you don't have a limited slip rear end, which ever tire has more traction will stay in one spot and the other will spin. Path of least resistance, really. A limited slip rear will let both tires get power.

I really don't think your problem is the suspension, I've put my truck up some steep, slick inclines and not lost grip.

Also, I run my tires at 50PSI.

 

I brought up the suspension and tire pressure based on the comments I pulled above from the original post. If he can "put it in firrst and tractor up" it doesn't sound like it's basically a traction problem, it sounds like he can't keep his tires on the ground. Soft suspension and soft tires won't bounce as bad as stiff suspension and stiff tires.

And yes, I also think a working limited slip or locker would do better. He noted that both tires seem to spin fairly evenly, so it might not help a lot. But I've never seen an open diff work as well in poor traction situations as a limited slip or locker.

 

I see where you're coming from on that. But I think we might not be looking at the real problem, and broncoderek might have been on the right track...

OP...have you thought about maybe smoothing out your driveway some? If it's really that hard to go up that you can't pull 2nd gear because the truck hops all over the place, you might want to invest some time into your driveway...

 

The "driveway" is a mile long common road that costs about $8K /year to maintain. It's always bad this time of year as there needs to be a certain amount of moisture in order to be graded properly. It came with the 3.55s which are great street gears but lousy off road. I'd just as soon buy another truck than change ratios. I've kicked it into low range but that bumps up the torque & will bark them at the slightest blip. I didn't go with a larger tire which might work better because of the gears.
I'll drop the pressure even more & see if that helps. I have an old air shock compressor that I can carry in case I actually have to haul a load. The locker sounds enticing but if the rear end is in the air, it really doesn't matter how many wheels are turning. Even going downhill it will bounce so bad that the rear will try to pass the front. Does someone sell a 1/2 track conversion?