I bought a truck that was originally a single wheel which was converted to duals (I did not know this till last night, 2 months too late). It has a 3" adapter on the rear to offset the inner dual so that it will not rub the leaf springs then the wheels are bolted to the adapter. I know this isn't a good thing, and am rather annoyed that the guy I bought it from didn't tell me about this. The front was converted the proper way, but the rear worries me, will be pulling a gooseneck with equipment (tractors, bobcats, etc.) and need to know it I should replace the rear with a true dually rear.

 

Need more info. What year what model, tranny, engine gears etc.

In general you cannot really boost your tow capacity by using bandaids. You really need to look at the truck as a system with many components all contributing to the tow rating. Changing only one system does not increase your load capacity.

You can bandaid things and increase one or two systems but usually the rating does not increase overall.

Your dual conversion sounds like it is just a wheel adapter kit. If so, that is more cosmetic than load enhancing I think.

If you are serious about increasing the capacity(Not necessarily the legal rating) I would look at brakes, wheels, tires, axle, gears, cooling capacity, springs, shocks etc. Your biggest safety issues would be brakes, springs, shocks, wheels and tires. Durability issues are involved with all systems.

Note I have never seriously tried to increase my tow capacity, other than helper springs and that was when I didn't know better. So you could say I don't have any real world experience with these bandaids. I just read a lot. I do tow an 8,000# trailer with my F250 with correct ratings and I can speak with more experience there.

Good Luck,

Jim Henderson

 

I wasn't trying to boost the towing capacity. I didn't know it was like that until last night. I know that the kits pretty much suck and that only a true dually rear is the way to go, I just would like to know if this will hurt my towing capacity or will it stay factory.

Truck info
1990 F-350 4x4 Crew cab 7.3L ATS turbo, 3" exhaust, 5sp trans, no lift, believe 3.55 gears.

 

FireMarshal:

If you really have a 3.55 rearend, this is your limiting factor. My 94 F350 7.5l (gas) CC LB had a factory 3.55 diff and is rated for less than 8k towing. The previous owner changed the rearend to 4.10 and the manual says that a similarly equipped truck has a bumper pull capacity of 10k and a 5th wheel/gooseneck capacity of 12k. The extra rubber in the back won't hurt your capacity, but it won't add to the capacity if your still turning them with a 3.55 diff. Since the axle has been modified, he may have changed gears as well.
Determine your RPM at a given speed, and do the math to determine the gear ratio. My Excursion with 267/75R16 and a 3.73 is going over 70mph at 2000 rpm, but my F350 with 235/85R16 and 4.10 is going about 65mph at 2000 rpm. If you've got a 3.55 you should be going close to 75mph at 2000 rpm in OD.

Dan

 

Well, mine must have the 4.10 gears then. It isn't the fastest. I am running about 2500 rpms at 70 mph. I haven't found the tag on the diff, so it may have been changed or whatever. Thanks for all the help guys.

 

Assuming the dual conversion is not a weak link, then your truck will have the same rating as before. I just worry about the cheapie dually conversion kits and whether they have at least stock strength.

Good Luck,

Jim Henderson

 

As stated, your truck will still have the same GVWR as before the conversion.

 

I guess the first thing would be to find out who made the adapter by taking it off. If it says made in CHINA you might want to think twice about it running it just street driving.

Personally, I would not run an adapter on any tow vehicle. Using the adapter you are placing the load out beyond the axle instead of over it. It is a question of leverage and why on all DRWs I have seen (Ford and Dodge) the rear wheels come in over the axle and not out from it.

Also, there is the question of the adapter's strength and the load it places on the OEM studs.

From the sounds of it, this adapter has DECREASED the stock load rating, not added to it.

If you have real DRW rims, I would suggest a junkyard axle, rebuild it with maybe a locker/LS and once it is installed, sell the SRW axle and recover most of your money.

 

Alright, I have deicided. I have this posted in the pre-powerstroke forum also, and was given some very detailed info on sizes, widths, etc on doing this the right way. I will run them for the time being till I find another axle. Then do the conversion. However, I am still considering going back to the single wheel and putting a lift with maybe say, 36" on it . But I will wait and see what I can find.

Thanks for all the advice and help.