Dump Conversion -hits the differential with full load+bumps

[monoblock]

I have a 93 D250 DUMP conversion -from Pierce Sales. I have not posted about the conversion and the numerous adaptations required to get it to fit/work. It was so difficult I really didn't want to encourage any interest in the conversion !
One of the many difficult adaptations I made was to raise the bed height 1"+ to make the dump hinges function. The other objective was to get the dump mechanism higher - to clear the differential under full load+bump. I failed.
The first 'full' load of rock that I hauled ,rolled gently over a whoop-tee-do at walking pace and the bounce smashed the dump scissor mechanism on top of the speed sensor that fits into the top of the differential. Of course that put the ABS and brake warning light on. The axle may have just kissed the bump stops. When I say "fully laden" obviously that is a guess. There is about 2+" between the bump stop and the axle but only 1" between the scissor arm and the speed sensor. To complicate matters(or help ) it has air suspension at the read and I was running at 15psi. I have now increased that to 25psi to raise the ride height.Obviously the un-laden ride quality has suffered but the clearance is better.
I had fitted a steel bracket above the speed sensor to protect it but 3/4 ton(?) of bouncing load 'modified' it's shape in one wallop!

Here are my questions
1. is there an alternative location to fit the speed sensor that is in a less vulnerable location? No, I didn't think so.
2. how can I 'hack' the system so the ABS still works without this sensor? Put one on the trans? No, I didn't think so.
3. Is there a more compact one I can fit instead of Dorman #970012 ?
And a helpful hint for others who need this part. The price is almost $80 on some sites.Rockauto has it for less than $10 if you use their discount code.
Grateful for any comments on the speed sensor issue. I really dare not comment on the Pierce Sales dump conversion kit because sadly ,I have nothing good to say about it!

[PToombs]

#1 and 2 you have answered yourself. #3 I don't know, probably not.
I'm going to throw a few things out here, maybe something can help you.

If you aren't in love with the ABS, unplug the box behind the glovebox and the lights will go away.

You could use an air leveling valve from a big rig to adjust the air bag pressure. As the truck drops, more air is added to the bags to keep it at the same height. I had this on my truck to compensate for whipped springs. It took 40 psi to hold the truck level with the bad springs, but if I added any load, the pressure would go up more to keep the truck level. I had a load of firewood on once and I had 120psi in the bags. I shut the compressor off because the pressure was climbing and the bags are rated 120psi. I drove it home with no problems. You could set it for 0 or a few psi empty, and keep an eye on it as you load the truck to watch pressure and clearance to the axle. It will still bounce when you hit a bump, but it should have more clearance than before.

Are you able to put a spacer on to raise the hoist sub-frame any? I know larger trucks all have a wooden spacer (usually 2") between the main frame and the sub frame whether it's a flatbed, dump truck, or whatever.

Hope something here helps you out.

[monoblock]

Mr.Toombs,
Great ides!
The air leveling valve+compressor is a great idea. I already have a 12v compressor that I carry in the truck for the purpose you suggest but it would be a great modification to make it a fixed+automatic device. With a pressure gauge and control valve in the ab it would be pretty slick!
There is not any more space for spacers unfortunately. I did some radical surgery just to get it the way it is. I'll try your other suggestions and that may suffice. Thanks for the suggestions.
I hope other Forum members may be able to take advantage of the low price I found for the speed sensor.

[DodgeFreak]

I wonder if you could relocate the sensor to the rear cover?? If you're good with measuring I'm sure you could do it.

[monoblock]

Good suggestion.Thank you.
The rear cover would have been a much more protected location from the outset. I wonder why they did not use it? Perhaps the tone wheel teeth can not be 'seen' by a sensor entering from the rear cover. You would have to measure on a partially stripped down diff. The clearance between the tip of the sensor and the teeth is critical. Interesting idea nonetheless. Thank you.

[PToombs]

I have a Viair compressor on my truck with a 3 gallon tank and air horns. Putting on the bags was a no brainer. I replaced the springs last spring ( ) and removed the bags and the truck rides better. I may put them back on for more load capacity. I have a pressure switch in the system, on at 120 and off at 145psi, it just does it's own thing and I don't worry about it, the tank is always full. It's funny when people say, "something is running on your truck!" and then it shuts off or it is off when they get back to it.

If you want to measure the clearance to the rear cover, put some Playdoh in between the tone ring and the cover and bolt it down, then pull it back off and measure the distance in the Playdoh. It's how they check piston to valve clearance in engines.
And the rear cover is a worse spot! It gets hit with brush, mud, and whatever else is in the way when backing up.

[monoblock]

Thanks for the info. I found a suitable Viair system based on your description:
http://www.viaircorp.com/10000.html

[DodgeFreak]

And the rear cover is a worse spot! It gets hit with brush, mud, and whatever else is in the way when backing up.

I wouldn't say it is a worse spot because brush and mud wouldn't damage it as much as a piece of steel coming down on top of it. You could always build a shield around it and bolt using the cover bolts. If it were mine I'd unhook the abs.