I have a 95 F250 4x4 that I converted from a 5.8 auto to a 7.3 5 speed. The truck currently has 4.10 gears and pulls like a freight train. I am going to change from the ttb front to the dana 60. I have a kingpin 60 with 3.55's. I need it to pull a 7000 lb camper through the hills of WV but other than that all of its towing is here in north east OH where there are no real hills. Does anyone have any thoughts on the 3.55's or should I look to trade it off on a 4.10 front ? I have both rears so other than loosing my limited slip rear it is no big deal.

 

For towing, I would stay with the 4.10s. I live in WV and I love my 4.10s for towing. Even on flat ground I'd rather have them than 3.55s. My son-in-law has 3.55s in his '97 CC PSD, and he used to like them, but he has started towing with it a lot and now he wants to swap to 4.10s.

 

I'd keep the 4.10's

 

I tow about 5-10k somewhat regular in Columbus, Oh with 4.10's. absolutely love them for towing. I also drive this truck everyday and a lot of that is with a load a 1/2 ton could easily handle. I still wouldn't trade for 3.55's if you paid me. Just my .02

 

I agree with the majority, 4:10's all the way with towing. Look at my signature picture.

 

IMO, going to 3.55s with your 5 speed would be fine for towing and will give you better mileage when empty. Keep in mind that an E4OD w/ 4.10s has about the same final drive ratio as the ZF5 w/ 3.55s. They cruise at close to the same engine speed in overdrive.

Auto with 4.10 guys. What RPMs are you turning @ 65mph and with what size tires?

4.10s are nice pulling gears, but without having that OD ratio of the auto or a gear vendors I wouldn't like them b/c of cruising engine speed. If pulling is 95% of the trucks life, 4.10s fo sho. 7000lbs isn't all that heavy though..

 

Not sure if it helps the conversation, but I have the auto tranny and 3.55s and I run at about 1700 rpms going 67 on the highway. I get about 18mpg regardless of where I am driving. In the steep hills its a little worse and i am going to Florida this spring on a trip and will get to see what it does on the flats. It pulls pretty good but I am not a big tow person so I don't have a lot to compare it to. FWIW

 

My '96 is 3.55 5 speed and 7000 ain't heavy in WVa. Since I live near there, It is when I'm
' pulling twice that is when I would rather have the 4.10. I plan to add a second 5 speed for gear reduction. If I was looking at changing both differentials perhaps 3,73?

 

Here's some quick calculations I did... All calculations done assuming 31" tires.

E4OD, 3.55s- 1776 rpm @ 65 mph
E4OD, 4.10s- 2051 rpm @ 65 mph
E4OD, 4.56s- 2281 rpm @ 65 mph

ZF5, 3.55s- 1901 rpm @ 65 mph
ZF5, 4.10s- 2195 rpm @ 65 mph
ZF5, 4.56s- 2442 rpm @ 65 mph

Guys that like 4.10s with the auto should like 3.55s w/ the ZF5 plenty good. Guys who like 4.10s with the 5 speed should like 4.56s with an auto. LOL With a ZF5 and 3.55s you would have to run about 70mph to run the same engine speed as an auto with 4.10s running 65.

 

With my auto, brand new Cooper 285/75/16's and 4.10's, I'm seeing around 6200 at 65. 70mph and higher and I can watch the fuel gauge to down.

 

I don't think you meant 6200 rpm or 2600 rpm. How many rpms are you turning? LOL

 

Poor motor. Lol

 

Fingers must've gotten ahead of myself...hell no, my truck revs like a 4 banger! Lol.

2200 @ 65

 

Mine went from 2030rpm at 75 with 3.55's, to 2360 with 4.10's. 65 was 1750ish iirc to about 2050.

 

Have you checked your speedometer? From what I'm coming up with for your truck, with 4.10s, 0.71 OD ratio, 32.8" tires, 2200 RPM puts your truck at 74mph. LOL. Every 4.10 auto truck I've driven has been barely over 2000 RPM at 65mph.