1991 super duty rear ratio

[towcat]

Just to clarify it is a 1991 F-super duty DRW chassis cab. It now has a 10.5' utility body with a 4k lbs. capacity crane. For my purpose I like the larger storage of the DRW utility body and the crane. As I said I am not interested in towing heavy equipment etc. The truck is in great condition with 106k miles. It will last me many years. As it is with a regular (for me) working load first gear is useless. So it is like having a 4 speed trans. In the next month I am going to order 4.10 gears and give it a try. Unless someone who has done it can tell me that they tried and it just won't work for whatever reason. Two manufactures of aftermarket gears have reviewed the build number of my rear and say their gears will work. I won't trash the 5.13 gears and can always put them back if I hate it for some reason. Thanks for everyone's input and I will report back when the swap is complete or found to not work. Doug

if you can get part numbers, i'd appreciate it.
what is the tare on your truck? my carrier is at 10k/lbs empty. 1st gear starts is not an option.

 

[Shadetreemechanic]

if you can get part numbers, i'd appreciate it.
what is the tare on your truck? my carrier is at 10k/lbs empty. 1st gear starts is not an option.

Yes, I am interested too. If someone is making aftermarket gears for this axle that would change my opinion of my parts truck.

 

[franklin2]

If they are making a custom "thin" gear, it may work. Like I said, you need a larger pinion gear, so they must be making the ring gear thinner so in effect, they are making room for the larger pinion.

 

[Drollins]

I really wish I could purchase the R&P from all three of these company's. All of them were helpful and professional. They all have parts for pre 1998 Dana 80 rears. It is a busy season for us at work so the F-super duty is really a winter project. It doesnt really need anything except a paint job to match other company vehicles. I am excited to install the new drive ratio. But I am not sure when i will get to it. The case break is 4.10 and up to 5.38. A 3.73 is available for the high ratio case using a "thin" ring gear. The low ratio case is 3.73 and down but a 4.10 is available in a "thick" gear. I have ordered the 4.10 gears. I think that will get the RPMs down to a reasonable level at highway speed. About 2000 rpms at 58 mph. I wanted to go with the 3.73 but I was afraid that might not have enough power starting off a heavy load. So I think the 4.10 will be best for my needs.
http://www.ringpinion.com/
http://eastcoastgearsupply.com/
http://www.nationaldrivetrain.com/
I really appreciate the input of those interested in helping.

 

[1466IH]

if you decide not to mess with it i would be up for a trade for my sig truck

 

[Drollins]

I don't think I am interested in a trade but tell me what you have. Mine is super straight no rust, clean, not abused, fleet maintained, and 100% stock w/106k miles. The only down side is no A/C but we will probably install that in the spring. I don't think the truck is wrong for my application. I like the larger storage and crane. So if a trade was considered I would be keeping my utility body w/crane.

 

[riotwarrior]

Watching this close as this type of scenario and information is good to know once proven out.

Now as for the OP swapping rear diffs, that would entail he then has to carry two spares as the truck should have 10 bolt wheels. Swapping to a different diff, say a 10.25 or 70 means that he's got 8/10 bolt combination so lets not go down that road, plus the loss of resale value, plus most important, lesser brakes.

If they tell you you can purchase a R&P for your truck say 4:10 and nothing wrong with that gear set at all, then I would also ask them if they can recommend a qualified shop to do this install for a warranty worthy installation.

That is if you your self are not qualified to do the installion and such.

Well just thinking out loud here cause warranty on workmanship and parts is well worth the investment sometimes!

JM2CW

Al

 

[1466IH]

oh i wasnt really serious i have too much work into my bed and truck the only way i would trade is for a 2&1/2 ton truck with a 10k crane mine has the auto crane 6006eh now its rated for 6k

 

[Drollins]

Al, I totally agree with your comments and thanks for your input. Installing a different rear was not something that interested me and I would have probably just lived with the high revs. A 4.10 gear set will be a great ratio for this truck. After using the calculator on www.ringandpinion.com I can see it will leave plenty of low gearing to start a heavy load. Just not the stump pulling of the current 1st gear that is useless 95% of the time. I will do the install. We do a lot of that type of work with marine transmissions and outdrives. So things like bearing preload, proper contact pattern and shim adjustment are a regular thing for us. However I have never done a differential before so it will be fun to learn something new. I will report back when it is completed.

Watching this close as this type of scenario and information is good to know once proven out.

Now as for the OP swapping rear diffs, that would entail he then has to carry two spares as the truck should have 10 bolt wheels. Swapping to a different diff, say a 10.25 or 70 means that he's got 8/10 bolt combination so lets not go down that road, plus the loss of resale value, plus most important, lesser brakes.

If they tell you you can purchase a R&P for your truck say 4:10 and nothing wrong with that gear set at all, then I would also ask them if they can recommend a qualified shop to do this install for a warranty worthy installation.

That is if you your self are not qualified to do the installion and such.

Well just thinking out loud here cause warranty on workmanship and parts is well worth the investment sometimes!

JM2CW

Al

 

[Drollins]

towcat, I will keep all the necessary info and post here when it is complete. I see your carrier is basically the same set up. We are only looking at about $450 worth of parts for the gear set and shim and bearing kit. It should not need the pinion bearings but it will save time and be easier than removing the old bearing from the pinion shaft. I am not sure of the tare weight. I just purchased the truck a few weeks ago and we won't use it much until it gets painted and lettered to match the other trucks. I do have a few of scrap engines to take to the recycler and maybe I will take the new truck. Then I will get a tare weight when I am unloaded. Thanks!

if you can get part numbers, i'd appreciate it.
what is the tare on your truck? my carrier is at 10k/lbs empty. 1st gear starts is not an option.

 

[Drollins]

I am not sure where you are going with this. There is not much tare weight difference between an f350 DRW and a f super duty with my utility body and crane on either chassis. A 150 or 250 would not accommodate the utility body with crane that we have. I don't feel like I made any mistakes. I like the truck just not the gearing. I was asking for opinions about gear ratio change to make the truck suit my needs just like most others on here have done with other mods. I find you post interesting coming from someone who bought a f250 SRW and tried to turn it into a f350 DRW. Do I hear a little chassis envy?

agreed.a mistake was made in the purchase of the vehicle.no need to continue on,when it's likely it could be sold and the correct truck (f150-f350 pickup) bought for about the same money or less than trying to make an f-super more pickup truck type hwy friendly since it's gross weights are just not required.sometimes is cheaper to admit our mistakes and simply move ahead rather than live with them.

 

[FORDF250HDXLT]

I am not sure where you are going with this. There is not much tare weight difference between an f350 DRW and a f super duty with my utility body and crane on either chassis. A 150 or 250 would not accommodate the utility body with crane that we have. I don't feel like I made any mistakes. I like the truck just not the gearing. I was asking for opinions about gear ratio change to make the truck suit my needs just like most others on here have done with other mods. I find you post interesting coming from someone who bought a f250 SRW and tried to turn it into a f350 DRW. Do I hear a little chassis envy?

the info about the utility bed wasn't posted until latter.
i didn't try anything.i did convert to a dually lol.if i wanted a heavy 2wd super duty id buy one.i was sincerely trying to help.not tell you what to do.

The only down side is no A/C but we will probably install that in the spring. I don't think the truck is wrong for my application. I like the larger storage and crane. So if a trade was considered I would be keeping my utility body w/crane.

 

[Drollins]

The OP stated the utility body. I was only making the point that my opinions about what makes the truck better can be different from yours. Negative comments like "downgrading capabilities" and "a mistake was made" are only an opinion and not helpful. Others may view it as upgrading capabilities since it will improve highway drivability. Clearly there is a trade off involved.

the info about the utility bed wasn't posted until latter.
i didn't try anything.i did convert to a dually lol.if i wanted a heavy 2wd super duty id buy one.i was sincerely trying to help.not tell you what to do.

 

[PackRat239]

Good Info

 

[Drollins]

Towcat,
Just unload a bunch of scrap metal yesterday. My truck was 10,400 lbs. with a normal load of tools etc. in the utility body and the bed empty. So just about the same as yours. What sort for fuel mileage does your carrier get with the 5.13 gears?

if you can get part numbers, i'd appreciate it.
what is the tare on your truck? my carrier is at 10k/lbs empty. 1st gear starts is not an option.