4:10 vs 3:55 rear

[Diesel Boy]

I have the opportunity to purchase a 2002 4x4 truck. It has all options and the color I want. However, it has a 4:10 vs 3:55 rear and automatic trans. What fuel milage difference will I see and RPMs on the highway? My current truck has the 3:55 and gets 20 hwy in summer and 15 in winter. Will hwy RPMs be like running my current truck out of OD?

 

[georgej]

Here in the NW I'm currently getting 15+mpg up from about 13. 5-14 last year when the truck was new. It's a 3500 with 4:10s and auto. Last summer 19. 8 empty,13 towing at 60-65,10 towing over 70. The trailer weighs 7000lbs. ready to roll!I do drive like the 62 year old I am!









George

 

[JBevans]

I don't have the auto so I don't know if this will help or not. I have a 2001 with the 3. 55/ 6-speed. I usually run 2000 RPM at 70mph and get around 15-16 mpg in the winter and 18-20 mpg in the summer. So far I am pleased. Love my truck.

 

[Barry]

That truck has the perfect set-up. Sooner or later you will probably have larger tires installed. If I were a stocking dealer I would never order an Auto/4X4 with 3:55s unless it was a sold ordered unit. Get it before it gets away.

 

[KatDiesel]

I would go for 4. 10. If ya don't like the rpm's you need to run then you can just put some bigger tires on to compensate for it. The auto + 4. 10s is a really nice setup.

 

[NVR FNSH]

I've got 4. 10s & 315/75s on my '00 6 spd. I'm doing 66mph at 2000rpm. I'm seriously considering a Gear Vendors.....



Brian

 

[chuck3]

My auto with the 3. 55 gears runs 2000 rpms at 75 mph, I like it because in 3rd lockup I can run 55 mph at about 2100 rpm.

 

[Okie-Go]

I have a 6spd and 3. 55's. I have talke to people with auto and 4. 10 and they love it. If I ever buy an auto it will have 4. 10 in the rear.

 

[Fireman Dave]

I'm with Chuck...

I like my 3:54s for the same reasons as Chuck. They're great for the long bobtail highway trips at 75mph, and they're also nice for towing out of OD. If I were planning to put on bigger tires, then I'd probably go with the 4:10s.

 

[LSMITH]

I would not even consider another automatic with 3. 5 gears. I think Barry is right, an auto NEEDS 4. 10 gears IMO regardless of what you use it for. The auto with 3. 5 gears is miserable unless you upgrade the TC and VB. The ETH/DEE combo is the same price as an auto, that is a no-brainer to me now that I have put 90K miles on mine. I have 33's on mine and would like 35's but it is too high geared already with the 3. 5's. With a manual transmission I would get the 4. 10 if a 5 speed and a lot of towing, with the 6 speed I would get the 3. 5 regardless of tire size. I would not even consider another automatic transmisson either, I hate mine. The manual trans is the way to go IMO.

 

[NVR FNSH]

Towing my 36ft/14K gwr 5th wheel the 4. 10/315s/6spd work out great. Normal driving is where the 4. 10s are a drag and the 3. 54s or GV would be the way to go. 315s are not tall enough to make a significant dent in rpm - I figured they would be... ... Hence, the reason I'm looking at a GV.



Unless you are towing heavy all the time I would seriously consider the 6spd/3. 54 combo and mildly bomb the engine to make up for the gearing. Chuck Arnold at the Power Shop talked my dad out of a GV for his '96 5spd/4. 10 - went with a Banks kit and my dad is very happy towing his 36ft/15k 5th wheel.



Brian

 

[Snow man]

I have the 4. 10,and automatic in my 2500 4x4,quad cab. I feel its perfectly geared. You will see about2200 rpm at 70 mph,2500 at 85 mph. The 3. 55 is ok with 245 tires,but the new trucks have 265 tires,and i put 285's on mine,which makes the gearing equal to a 3. 90,perfect for my driving. As for mileage, i get 15-16 in mixed driving with a heavy foot,i drive 80+ in the interstate,and i let it idle a lot

 

[MikeR]

The . 69 overdrive in the auto is too steep as it is with 3. 54 gears. If you ever ask THE transmission guru, he'll tell you that 4:10's is the better choice in the auto.

 

[RADdodge]

It's Just Right!

Most replies here have hit the nail on the Head. If you even vaguely think you might want larger tires on your truck someday, go with the 4. 10. I run 35" tires and run about 73mph at 2000 rpm. It's a nice ride. Great too in 3rd in the mountains when you can't keep it in OD range above 62 mph.

 

[dewdo]

If you plan to tow or haul with it I would go for the 4:10. It is easier to replace the tires than a rear end in case you decide to haul or tow at a later date. Also I thin the 4:10 has better resale.



Dewdo in the other Washington

 

[24V-DSL]

Yeee..haw

DTT auto, 4. 10's, and 285's.

 

[Turbo Terry]

Get the 4. 10 with the auto. Wish I did. 3. 55 lug to much. IMO

 

[vinconco]

Will the larger (285)s fit the stock wheels?

 

[Alan Reagan]

Check out the article by Jim Anderson (?) in the new issue of TDR. That may help with your decision. I had the 4. 10 in my 98 auto and now in my 01 with a 6 speed. As Mr. Anderson points out, the sweet spot on the 24 valve engine is around 2200 RPMs. That's 70 mph with the 4. 10. I get 21. 5 empty. Towing mileage varies with load and type of trailer (wind resistance). Towing I get as low as 14 and as high as 17. But with the 4. 10, especially on the two lane roads, I don't have to down shift very often. At 55 I tach around 1800. That's a good range to tow on two lanes. Any lower and I would lug when I hit the hills.

 

[kchristopher]

I think almost everyone will agree to go with 4. 10s if you have an auto, expecially if you want to go with bigger tires.



The disagreement comes into play with the manual transmission.



If you tow more than half your time and have a 5 speed, you may want to consider the 4. 10s. It would make the 3-4 split easier.



If you tow more than half your time and have a 6 speed, I wouldn't be so quick to jump on the 4. 10s because the gear splits are pretty good.



If you tow infrequently and have a manual transmission I wouldn't consider the 4. 10s, even if you were considerend a swap to the common 285 or 315 tires.



Look at my truck specs in the sig. For those who aren't familiar, the 255/85 tire is the same height as the 285/75 that alot of people are switching to (but don't really fit well on my puny 6. 5" wheels), they're just narrower. That means I can drive 60mph in 4th gear at about 2100-2200 rpm. Or I can drive 70mph in 5th at 2000 rpm. Since I don't tow that often, I don't want to give up reduced revs at highway speed (see the NVR FNSH post). Intead, if I'm not on the interstate, I can simply drive in 4th gear. If I'm on the interstate, I'll probably tow at a speed that will allow me to use 5th gear. If I were to tow in mountainous terrain (east coast style) and had trouble using 5th, I would pay the $300 to get a new camplate before I would go with the 4. 10. I understand that the 24v people can also upgrade at similar, but maybe slightly higher prices. This may or may not work on west coast style mountains, as I've never driven out there.



Key point - I think that some people forget that just because you have 5 or 6 gears doesn't mean you have to use all of them all the time. If you can't tow in OD, drop to direct. Yes, the split in the 5 speed isn't the greatest, but everybody I talk to how has upgraded power says it makes it a breeze. The 6 speed split seemed great to me as is.



My ultimate combo - my truck with #11 plate and USGear OD. Then I could tow in 4th over, which is just slightly lower than 5th and not worry as much with lugging it. 5th over would be a good highway gear when empty - that would put me at about 1600 rpm @ 70mph, right about torque peak in a 12v.