4.10's to 3.55's - Should I do it?

[912504x4]

what about your extra parts

What are you gonna do with that Dana50 4.10-1 pig housing :Sly :Sly ?

I may be in the market for one in the spring when it will be warm enough to do the job. I had also hoped to find a 60 instead but if the price is right it will be worth it for me to use as a temporary fix.

Just checking,
Eric

 

[bikepilot]

I'll keep it till I'm sure I like the gear change, then most likely I'll unload it pretty cheep:Sly

I'll probably swap the diff's, but keep the actual "I-beams" that are on the truck in their place -whatever looks easiest when I start. Either way I'll have enough parts left over to assemble and entire D-50 front end with 4.10 raito.

 

[MIDNIGHT RIDER]

How on earth are you guys getting the types of fuel mileage that you do??

I have had my 85 F-350 4-sp 3.55's for 20 years and have never got over 10mpg pulling stock trailers - loaded or empty.

I have never had opportunity to check mileage of the truck without trailer; but it doesn't seem to be much better.

There are plenty of these trucks around here and most get mileage like mine; so I figure it must normal.

 

[highest_vision]

How on earth are you guys getting the types of fuel mileage that you do??

Join the party! I have 3.54 and never get above ~12 empty, no matter how I drive. Pulled a small trailer to nashville and got 9!
James

 

[912504x4]

Overdrive is a wonderfull thing! I am sure it has helped my mileage out alot.

 

[The Warden]

Overdrive is a wonderfull thing! I am sure it has helped my mileage out alot.

You can say that again!!

I just did a speed-run yesterday to L.A. doing 75 to 80 most of the way...and still got 16mpg. Granted, I was empty, but even still. I couldn't even get above 75 with the T-19!

 

[bikepilot]

Yep, OD here too. I run about 2250rpm at 75mph, just want to get that at or just below 2k rpm now

 

[Mikes91]

I'm running 285s with 3.55 gears. I've wished I'd had 4.10s on numerous occasions... especially when loaded with 10,000 pounds and trying to accelerate out of 30-50mph.

God it is just terrible between those speeds.

Keep your 4.10s and keep the speed down, IMO, unless you're doing lotsa interstate driving.

Now, that said... I *have* been getting roughly 18mpg unloaded at interstate speeds, and 12-13 loaded with the horse trailer at interstate speeds. Hanging with traffic--about 75mph. I guess it depends on how much highway pulling you do. I'd probably be most happy with a 3.73 compromise on my truck... might be something you'd consider.

Mike

 

[bikepilot]

That's the thing, I do 99% interstate driving with light trailer. Driving to and from FL at 55mph is no fun (I've done it). Sounds like 3.73's and big tires or 3.55's and stock tires would be a good setup.

 

[beretzs]

I think you would be fine with 3.55's, heck, you have gears in your transmission, you can always use a lower one if your load is too heavy. These engines make alot of TQ, so you can use it to your advantage, and get some good fuel mileage.. Looking back, I wished I would have kept my 3.55's and added the GV to that, then, I would have gotten good freeway RPM's and still been able to drop a gear or two and get some great pulling power.. Scotty

 

[bikepilot]

Makes sense

Though I'd love to keep the 4.10's and add a GV, but that's more $$ than I have or want to spend on the truck.

 

[beretzs]

No kidding, if I had to do it all over again, I would have left the truck stock height, put some nice tall 255/85R16's on the truck, put the GV's on behind the C6, and left the 3.55's. I would be getting dangerously close to that 20MPG mark and have a great cruising truck. Oh well, live and learn. Scotty

 

[beretzs]

You know, thinking about it, you maybe better off doing the exhaust upgrade for your turbo, getting your intake cleaned up a little, meaning more cool air and get a really good exhaust built up for your truck, and you should bring your economy up a few points. Reason being is the E40D when pulling weight and in the hills will really be straining with 3.55's. Don't know, hard call. You are getting really great mileage now, you may get a little better mileage with the 3.55's but you are going to negate it to some extent with driving faster and such.. Plus, if you ever get something heavier than the bike trailer, you will really want your 4.10's back. Man, I am indecisive enough for ya ha... I would throw your money at stuff that will get you more efficient power and you could gain your mileage. An intercooler would be great, should be able to pick up a MPG or two with some tweaking. Scotty

 

[shorthair]

fuel economy is directly related to my right foot, i'm not the quickest by far & i very seldom turn more than 2,000 rpm even when getting on the freeway when MT loaded i'll run er up over 3,000 if needed. so even stop & go on my daily commut i can get 18 mpg.

 

[bikepilot]

Good thoughts Scotty - my main point in thinking about going to 3.55's is to enable me to drive faster with less mileage penalty. I'm totally happy with 20mpg, but not happy with 55mph. Right now, if I drive 70-75mph I get 13mpg and even at 65 I only get ~15-16mpg. Its my hope that I can manage ~20mpg at 65-70mph with the gears like Soulpatch.

I do intend to do the ATS turbo housing/downpipe upgrade and make a better intake sometime, but right now I have very little to spend on the truck. I got the front end for free and if I can find rear gears cheep somewhere it will be a cheep and reversible experiment.

Eventually, I intend to have it set up so that it turns less rpm at speed and has the mods you mentioned. The only real decisions are how much less rpm, how to lessen the rpm (GV, tires, gears) and what order to do the stuff in.

I'd prefer a GV to gears, but it looks like I can do the gears for under $200, a GV would be a lot more than that. I like the looks of big tires, but don't really need the truck to be taller (or want the extra work when it comes to loading and unloading stuff, or want to put the extra stress on the steering stuff).


I'd love to go ahead and open up the intake, but I don't really have any sheet metal fabricating skills or equipment. Any ideas on that one? I've noticed that the stock intake is definitely restrictive. After towing up a decent grade the "dirty filter indicator" thing is popped half way, even with a clean new filter - indicating that there is a significant amount of vacuum being pulled in the air intake.