I bought a 86 F250 a few weeks ago. Its got a T-19 trans and a 10.25 rear end. I noticed that when I'm doing 65 or 70 it just does not seem like I'm actually going that fast. So I tested it with my GPS. At 70 I'm actually doing 60. I checked the rear axel and found out its got a 4.11 gear. It should have a 3.55 gear.
If I was doing a lot of towing I would say ok thats good. But all I tow is a 18 ft boat on the weekends. This truck is going to be a daily driver and I need to get some MPG's out of it. (I drive 70 miles a day)I've started looking for a 3.55 ring and pinion for it but a friend suggested I get a 3.08 gear. Can I get a 3.08 gear for a 10.25 axel? If so would this be overkill? Does anyone else here have a 3.08 in they're truck? I would like to see what my MPG would be with that vs. a 3.55 gear.

 

3.08 is available for the Sterling, would it be over kill ... that would be debatable.

The 3.55 is a good gear for all around use IMO.

-Enjoy
fh : )_~

 

David85 has 3.08 gears, he likes them. Keep in mind that he pulls a trailer with those, and his transmission is an E4OD with a 2.71 ratio in 1st gear - your T19 has a ratio of 5.11 in 1st, so methinks you'll have no problems getting the truck and boat to move even with 3.08 rear end.

 

Thanks.... I think I will try the 3.08 gears. I'm really shooting for MPG's. I just want to make sure I can still pull my boat out at the boat ramp. I'm not sure when I will get to change the gears but when I do I will update. Hopefully in about a month.

 

i have 3.55 knock down to a 3.07 active ratio cause buy my 37 inch tires with a t19 i have no problem geting started on linclines and pulling my dads 25 foot ranger boat out of the boat launch

 

what size tires are you running polacko?
how much does your boat weigh?

 

how hard is it to swap 4:10 for 3:55 I don't tow anything ginormous and need to get better mpg

 

with your 4wd dually,you would want to buy gears and have a shop with the proper tools install them front and rear.

with a 2wd truck,you can simply swap the whole rear axle with 3.55's from a salvage yard.
i could suggest doing this with at least the rear,but with a dually axle they cost more.
still i sure would be pricing it each way.keeping in mind new vs used,the potential sale of current DRW axle etc.

its not something to take on yourself.special tools required,and skill.
swapping the whole axle however,front/rear both you can do that yourself of course.

it will take a lot of miles to pay back a gear swap in a 4wd DRW from 4.10's to 3.55's with a OD trans.
personally,i wouldn't do it.however if you could run taller tires,this will bring your gearing down.personally i wouldn't do that either as the taller the truck is,the harder on the back it is when loading the truck.
if thats not a concern,consider gear swapping using tall tires.this would be your best bet.
a tire height of 36.5" would bring your gearing from 4.10's to 3.55 (3.56)
so say you could fit a 37" tall tire under there,you would have a 3.51 actual gear ratio.
however,you don't want a wider tire either,as they hurt fuel economy (so does going up in general as well.so as you can see,a gear swap and stock height is best fr fuel economy gains.)

whats the tallest tire you can fit under the stock f350......anyone?

realistically powerstroker,your kinda stuck with 4.10's unless you want to pay or swap both axles,then sell current axles.likely,wouldn't cost much swapping both axles,and then selling yours with lots of time hunting the deals.however thats some work involved.

short answer for your truck: difficult or just expensive.you pick.
DRW is also hurting your fuel economy vs same rig w/SRW.

 

i got a 3:55 10.25 i trade for 4:10 -4:11

 

polako, is your truck 2wd or 4wd?

While I do tow with 3.08s, I have a low stall torque converter that keeps me from burning any clutch on hard uphill starts. I also have a transfer case I would wonder if you would have any issues with that boat in the ramps. I can pull our 18 footer rather easily in high range with my auto, but haven't heard of anyone running a T19 with 3.08s in one of these trucks so I can't be sure how it will perform. If there will be a problem, it will only be in the sub 20 MPH range.

I think there might be a way for you to figure out if your truck is still drivable under those conditions.

I'll need some confirmation from some of you guys because I am not 100% sure of the gear ratios found in the diesel T19 transmission so let me know if my assumptions are wrong.

With 4.11 gears and your transmission in SECOND gear, your final drive ratio is 9.9051 (assuming 2.41:1 2nd gear ratio)
With 3.08 gears and your transmission in 1st gear, your final drive ratio is 12.3816:1

How does your truck pull away right now in 2nd gear? can you live with how it performs like that? If so, you should be fine with 3.08s and using all 4 forward gears because 3.08s in 1st gives you more gearing than 4.11s in 2nd. I tested this myself before going ahead with my own 4.10-3.08 swap since I had no one else's experience to go on. So far no regrets. If you can actually get away with 3.08s in your truck, you will be amazed at the difference.

 

ouch looks like I'll stick with it then hhaha

 

Ratios should be as follows:
1st gear is 5.11
2nd gear is 3.03
3rd gear is 1.79
4th gear is 1.00

So with the 3.08s his overall ratios shifting through the gears will be 15.74 -> 9.33 -> 5.51 -> 3.08 whereas with the 4.10s he currently has 20.95 -> 12.42 -> 7.34 -> 4.10 so yes you are correct in that if he can currently get things rolling in 2nd gear then even with the 3.08s there will be no issues starting to move under load.

 

I thought the diesel had:

4.02
2.41
1.41
1

But whatever gearing set is assumed the spread between 1st and 2nd seems to be close enough to still use that test. Its hard for me to remember very well what mine was like with 4.10s and the C6 with all the traumatic memory suppression happening but I seem to recall 1st gear being basically useless. 30 MPH I was already in top gear and beginning the wind out RPM climb........what a horrible nightmare....

 

ouch! i do feel bad for people with this economy running that dated setup.
4.10's with OD isn't so bad,but 1.1 with them is worse than i figured it would be.holy cow.
my top speed would be 45 mph max (40 when i could get away with it) at all times for fuel economy if i had to live with that setup.

polacko,
have you considered a zf5 swap?
overdrive is worth its weight in gold with fuel at these greedy prices today.
a DD @ 70 miles per day screams E40D or zf5 swap to me,along with 3.55's.
id do the OD swap,and swap the whole axle from salvage yard back to 3.55 personally.just another idea to consider.

 

yeah with the c6 and the 3.55's she'll move anything she can get enough traction for I have no idea why you'd have wanted the 4.10's

one thing to consider is that it may be cheaper and easier to buy an axel with the 3.55's and swap em then to buy a ring gear and set it up.. depends a lot on if you have the skills to install axle parts