GEAR RATIOS?
 

I have a 91 F350 4x4 CCLB 7.3 IDI E4OD and an 88 F350 dually CCLB 2WD 7.3 IDI E4OD. Are the rear ends the same gear ratio, provided of course that they are stock? I want to combine them to make a dually 4x4.

They could be 3.55 or 4.10 ratio.You'll need to look at the tag on the rears.The axle code is on the door jam so you can look them up that way first if you rather.Just be sure to check the tags at some point cus rears could of been swapped at some point.

Did the '88 come with a pickup bed from the factory? If you want to use that dually rear,make sure it's a DRW pickup and not a cab and chassis.I dunno if they offered a crew cab C&C in '88 anyway (i think probably?) but just know it's got to be a pickup or it's too narrow to use as a dually conversion.
You can sell that 2wd diesel E4OD as you'll never be able to use in for anything.Might want to hang onto the spare 7.3l though.
Your front 2wd dually hubs wont do ya any good.You can sell those.You'll need some (much more rare) 4wd versions and or,and what I used,arrowcraft aa-4 front adapters (rugged as all get out!) to convert your front.This way you got the front dually rims and matching tires..........Though this isn't necessary and not worth while for a yard,just a beater,dump run truck.If it's a long lasting project it's nice to make it proper.Your rims and lug nuts from the drw will go to the '91 convert.

Thanks, I replied the day you posted this. I'm not sure why it never made it to the thread. As usual you are a wealth of information and a reliable patient teacher to the newbs on this sight (unlike others who use these opportunities to feel superior). I pulled the trigger on one of two parts donor trucks I've been looking at for a while yesterday, It was actually an 89 not an 88 but it was a factory dually F350 CCLB pickup 7.3 w/ E4OD w/ a 4.10 rear to match my 91. It's on a trailer in my driveway now. I will steal the radiator, steering column and dually rear for my project. I have to check out the motor and trans before I decide what to do with the rest. It will either be parted out/scrapped or maybe even put back together as a SRW 2WD CCLB Flat bed. That will depend on how many parts I wind up stealing from it before I get around to making that decision. Given that it only cost me $500 I can't really go wrong.

Thanks again, you have guided in the right direction on several occasions.

Smoking deal! I had to pay more than that just for my dually pickup rear.Your welcome.

Thanks, I originally saw the truck on craigslist, he was selling parts off it. I offered him $1000 for the whole thing which he refused. That was at least 6 months ago. The only part that has been taken off since is the left rear dually fender. I ran into him at a gas station and he remembered me and walked up and said he needed the room at his bodyshop and said $500 would work. That's when I posted this thread. When I needed the radiator I pulled the trigger and brought it home. It fell in my lap just like my 91. I must be doing something right. :-huh

here we go...this is embarassing
I asked a friend to crawl under the 89 DRW donor and my 91 SRW 4x4 to compare the rear ends. (I am disabled) He said they were the same. Apparently he was lazy that day or couldn't read. The 89 is a 4.10 ( I think) and the 91 is a 3.55 limited slip. I'm pretty sure both are 10.25" Fords but the door tag is damaged on the 89 so I don't know how to confirm this. I want to know if I can just swap everything outside the face of the end of the rear housing and do the front conversion, will that work to get me my dually 4x4? Where else other than the door tag can I find the axle code for the 89? Are the hubs different? I'm in over my head, I've never dealt with Ford rears before?:-huh:-huh:-huh:confused:

Maybe these will help.

https://cimg8.ibsrv.net/gimg/www.for...512be165e5.png

91 on left, 89 on right

https://cimg5.ibsrv.net/gimg/www.for...1209806572.jpg
91 4x4 SRW ABOVE




https://cimg6.ibsrv.net/gimg/www.for...b1baacf134.jpg
89 DRW ABOVE

Top pic is 3.55LS and the bottom is 4.10 open.

Yeah,your correct. If you removed the bolt under the tags you would see there is a "3" just before the ".55" and there is a "4" just before the ".10"
They are both 10.25 rears cus that's the only option for these year trucks. See the next numbers over " 10 and 2 ? This means 10.25 ring gear.

So to answer your question.No.You can't change anything over from the outside of the 4.10 geared DRW pickup axle to make your 3.55 geared SRW a DRW pickup axle.
What makes the DRW axle fit two dually wheels is that it's much wider overall than the SRW axle.

Now you have three options .
1.Take both axles to a shop to have their ring and pinions swapped This will probably cost more than the donor truck.
2.Swap the axle in and keep the new 4.10 gearing but now you'll need to change your D60 up front to a 4.10 ratio too.You may find someone willing to trade if you make a post here in the marketplace but you'll each be paying some $ in shipping unless you get lucky and find someone local to trade with.
3.Sell the DRW axle and use the money on the sale to find one with 3.55 gearing.

The DRW pickup axles with the 3.55 are not as common as the 4.10 gearing and (side note) I'm convinced they don't exist (in drw pickup form) after '92.

Thanks... not what I was hoping for. l will probably swap ring and pinions. I have several friends with good mechanics in their employ of whom I rarely ask a favor. It might be time to use up a big favor.

Looking at two statements in two seperate posts causes me to ask out of curiosity... Is the DRW cab and chassis rear the same width as the SRW rear?
In other words does the width difference only affect the use of the DRW pick up bed or does it interfere with the frame? I ask because a narrower DRW would work if it's just fitting the bed that is the problem, I'm going to be using a flatbed or hauler bed anyway.
This might sound odd but I'm not really looking to increase hauling capacity or width, I'm looking for the security of having four rear tires. I once lost a rear tire towing with a SRW F350 and know from experience how nasty that can be with a long heavy trailer. It spun me around completely before I knew what was happening. I ended up facing the wrong way, trailer and truck, on the shoulder of I-95. Thankfully I didn't kill anyone. A few days prior my truck had fallen from a lift and bent a rim at a NAPA service center near Tampa. They never told me, I found out when the rear tire came completely off at 70 mph. I found out later that the lift had collapsed after dismounting from the slab below.

If width doesn't matter what are my options?

NEVERMIND... THE SUN CAME UP AND I MEASURED IT ALL. CRAP! LOL

The reason a DRW cab and chassis can fit two dually wheels,is because the frame rail spacing is set closer together,along with those trucks having narrower springs.
Those rear axles wont allow you to run duallies on a pickup truck,despite what bed type you use.If you cut and moved the shock mounts on one of those axles to bolt into a pickup truck,you would just be back to where you were with a srw axle.

I pulled off the swap in one day today (big job for this cripple) but I'm exhausted and in a buttload of pain. All in all, I think it was worth it. IIwill attack the front conversion when I recover from today's efforts. Thanks again to all who helped!
https://cimg8.ibsrv.net/gimg/www.for...a5f34e0840.jpg
https://cimg3.ibsrv.net/gimg/www.for...cc628bd850.jpg
https://cimg6.ibsrv.net/gimg/www.for...5c77b42085.jpg