88 f350 gears?

[troy]

On a flat highway going 55mph in 5th gear my tach reads 2000 rpm. I know that some guys can go 70 at 2100 rpm. My tires are 285/70/16. I dont know if the recent owner regeared the truck. But I think this is a little high. I do know that he was running 35" tires . i recently bought a set of 22x11 rims. They have 37x13.5 toyo m/ts but 2 are worn and need to be replaced.

I dont know if i should buy 2 more 37 tires or buy a whole set of 35s due to the question of what gears are in the differentials?

Would any of you be able to calculate if these are just the stock gears or aftermarket? I dont want to drain and remove the diff. covers to read the numbers . the truck has a 5spd tranmission, 5th gear being the OD and it is 4wd

 

[troy]

Also i live on the big island of hawaii and it is mostly mountain here so majority of the driving is up hill and down hill .when it comes to long dist driving its somewhat flat

 

[Waystro]

Sounds like it has 4.10 gears what is the axle code on the door say?

My parents just bought a piece of land on the big island Pahoa to be exact basically it's a uncleared lot we plan to go over in March to start clearing.

 

[troy]

Waystro it says C5 under the blue word axle...so im guessing thats it

But wow pahoa is nice country. There seems to be more trucks like these on that side of the island .but they are either parts trucks or beat up ranch trucks

 

[riotwarrior]

2 people job w sidewalk chalk.

Mark tyre at road mark drive shsft mid poitn horizontilly one guy drives slow.... one watches drive shaft n tyre counting eavh time drive shaft goes round til tyire makes 1 revolution...easy peasy

 

[troy]

Riot warrior ... because i don't have stock size tires... Would there be a misreading?

 

[Waystro]

Ok according to this http://www.ford-trucks.com/forums/1053951-axle-codes.html
you have 4.10 limited slip. Rpm's still seem high for having a zf5 but I've never had a zf5 so can't say for sure. I know it's a different make but my Suburban in Sig has 4.10s and at 55 it's around 2000 Rpm's running bigger tires too.

Yeah a lot of farm trucks pretty decent prices too
Beautiful land over there.

 

[MtnHaul]

My axle code is C5 and it is a 10.25 with 4.10 and LS. Your RPMs sound about right. Check out one of the many RPM calculators online to figure your approx rpms at different speeds with different size tires. Just my two cents.

 

[riotwarrior]

Riot warrior ... because i don't have stock size tires... Would there be a misreading?

Not possible...once around of tyre = ×.×× rotations of drive shaft regardless of tyre size.

 

[MtnHaul]

dang--typed too slow.

 

[troy]

Ok being that it sounds like i have 4.10s . is it possible to run 35s without seeing too much of a performance drop? I have a feeling in my gut that if i put on 37s ill be climbing hills at 30mph in 3rd gear

 

[Waystro]

Personality I would go 35"
Bigger tires more resistance smaller less resistance.

 

[troy]

Yeah thats what ive been considering lately.. The 37s will clear the fenders when i make full turns but you are right Waystro that having the bigger tires will be more strain on the truck

 

[Waystro]

Might have missed it but size lift are you running? I would think at least 6" to clear 37s

 

[troy]

Idk the lift the guy put on is a bit wierd it has a 2" block with 2 shims that look like cut pieces of 1/2" steel and instead of only being 2 leafs theres 4 so and add a leaf kit and a 4th spring.
Im guessing it was a 6 in lift when it was new...but by the sag it has probably 4-5 now .but the tires did clear with a full 1¾ rotation on the steering wheel and theres ample clearance for suspension travel
There is a sticker on the drivers visor. It is a Superlift warning sticker about the raised center of gravity and larger tires and that will handle differently