which gears best for me - 3.55 or 4.10 - Diesel Forum

RoyLC · 11-24-2003, 03:53 PM

I have had some input on this already but would like to get a second opinion (no offense Bob)

Planned vehicle:
E350 EB class B motorhome (Sportsmobile conversion)
fixed high top
6.0L Diesel
weight - around 8500lb
4X4 (Quadvan)
stock size AT tires
typical cruising speed - SLOW - 55 to 60 mph
towing possible but not likely

What gears would give me the best hiway mileage?

I read somewhere (here?) that to get the best mileage you need to have this motor at about 2000 rpm. If I am driving 55-60 would the 3.55s put me at too low an rpm? If so, would not using the overdirve put me in the right rpm range or would that gear me down too low? Does anyone know how to figure engine rpm vs speed - given gear ratio and tire size, with and without overdrive?

HeyBob · 11-25-2003, 03:52 AM

[ QUOTE ]
I have had some input on this already but would like to get a second opinion (no offense Bob)

Planned vehicle:
E350 EB class B motorhome (Sportsmobile conversion)
fixed high top
6.0L Diesel
weight - around 8500lb
4X4 (Quadvan)
stock size AT tires
typical cruising speed - SLOW - 55 to 60 mph
towing possible but not likely

What gears would give me the best hiway mileage?

I read somewhere (here?) that to get the best mileage you need to have this motor at about 2000 rpm. If I am driving 55-60 would the 3.55s put me at too low an rpm? If so, would not using the overdirve put me in the right rpm range or would that gear me down too low? Does anyone know how to figure engine rpm vs speed - given gear ratio and tire size, with and without overdrive?

[/ QUOTE ]

Towing possible but not likely. 3:55 gears are what you want for the best mileage.

At www.differentials.com there is a program that figures gear ratio, tire size rpm etc.........

No offense taken. A 4:10 rear end in a standard van is for hard core towing only in my opinion.

Yardbrew · 11-25-2003, 03:54 AM

Roy,

Run a search on this forum and you'll find all the stuff that we have discussed previously on this topic. [img]/ubbthreads/images/graemlins/smirk.gif[/img]

Yardbrew

Larry M · 11-25-2003, 04:52 AM

Roy,

WELCOME [img]/ubbthreads/images/graemlins/biggrin.gif[/img] ... you've found the best place on the web to get all your questions answered by those that have been there and done that and the members here that actually own Vans are the greatest and most helpful group of enthusiasts you will ever find ... on to your question ....

As Yardbrew has indicated do a search in this forum using "3.55 and 4.10" using the "AND" search option and for all dates and you will get a wealth of prior discussion on your question. While all these discussions are for the 4R100 tranny the final drive and OD are the same on both the 5R110 and 4R100. If you look <font color="red"> HERE</font> is a table of the gear rations of the two trannys. Thus dropping out of OD in with either tranny should increase your rpms by approx 1.4.

With the 4.10 rear you will be right at 2000 rpms at 60mph which is were like you I also do probably 95% of my driving both towing and unloaded. Unloaded all freeway holding the speed to 55/60, I have seen upwards of 18.5+ mpg with my 4.10s ... not bad for a 4ton brick [img]/ubbthreads/images/graemlins/wink.gif[/img] However, I bought and spec'd out my Van specially to tow my 6.5K TT and driving habits (60mph) and I tow close to 50% of the miles I put on my Van and am absolutely satisified with my decision. Also, I can't remember, but I thought I could only get the LS in the 4.10 which for me was another consideration for my particular situation and is another decision that I am glad I went for.

With that being said and never having owned a 3.55 PSD (BigBob has both) it's really sort of up to you. I will say if you're not going to be doing much towing and want to scream around at 70/75mph most of the time you will be better off with the 3.55's.

Larry

msnunes · 11-25-2003, 10:32 AM

[ QUOTE ]
A 4:10 rear end in a standard van is for hard core towing only in my opinion.

[/ QUOTE ]

...or if you want oversized tires.

HeyBob · 11-25-2003, 05:17 PM

[ QUOTE ]
[ QUOTE ]
A 4:10 rear end in a standard van is for hard core towing only in my opinion.

[/ QUOTE ]

...or if you want oversized tires.

[/ QUOTE ]

Absolutely!!!!! [img]/ubbthreads/images/graemlins/biggrin.gif[/img] I couldn't agree more!!
[img]/ubbthreads/images/graemlins/smokin.gif[/img]
Now why didn't I think of that? [img]/ubbthreads/images/graemlins/shrug.gif[/img]

toalpi · 11-26-2003, 11:59 AM

A 4x4 Sportsmobile EB with a high top is NOT a standard van. Tony

RoyLC · 11-26-2003, 08:14 PM

Thanks for the help and welcome, guys. I will search the archives and get back to you if I have furthre questions. Tony, you are right that the Sportsmobile high-top is not a strandard van. Do you think that the 4.10 is more appropriate becaus of the size and weight of this vehicle?

kaleo · 11-27-2003, 03:43 AM

I would go with the 4.10. If you are like me you want 4x4 to get off the beaten path, sooner or later 31"s aren't going to be big enough.
If you don't ever plan on going with bigger tires or only care about MPG then the 3.55 is the was to go. I bought my van used with 3.55 and 245/75/16, it pulled good and got good MPG even for a 7.3 NA. Now it's got 35" tires and it's really a dog now. Can't save up fast enough for a turbo and new gears.