3.42 vs. 3.73 GEAR RATIO ???

GEP · Jul 10, 2003

Hi, I am looking at getting a used Chevrolet truck w/ 5.7L eng. and I can't decide what gear ratio to go with. I will be towing a 24' camper at times and a tow dolly. Do the 3.42 gears do a good job for towing power?
Any info will be helpful.
Thanks.

jwstewar · Jul 10, 2003

I can't say for sure, but I sure wouldn't want to go to that high of gear ratio - especially if you car going to be towing much. I'm guessing your camper weighs around 5500#s (which is about what our old 24 footer used to weigh). I used to pull our 31 footer with my 5.7 Z71 w/ 3.73 w/o any problems but I don't think I would have wanted to go w/ any less power either. I've now got a Silverado w/ the 5.3 and I went back with the 3.73. I think it is the best compromise between power and gas mileage. I also think w/ that high of gear ratio you may have problems w/ wheel spin in rain or snow.

BubbaJr · Jul 10, 2003

I totally agree. Another thing you may want to keep in mind is, if you are getting an overdrive automatic, and driving in the hills, your transmission will be constantly shifting in and out of overdrive. That is hard on it, so what you end up doing is putting in drive, and there goes your gas mileage.

shado · Jul 10, 2003

If you're going to tow something like that in moderate use, I would always go with the 3.73 or higher, especially when pulling up hills. But I have a 4.10 ratio in my 3500 Silverado Dually & I just hate it. I really don't pull that much very often, city driving is really bad on the gas mileage, at 35-40 MPH, the truck transmission stays in a lower gear, the RPM runs at 2000, same as if I was on a highway at 60MPH, & I'm basically on level ground. The overdrive does help some on the highway mileage, but I wish the 3.73 was an option for the truck when I bought it. Ford offered this ratio for theirs, but not GM. (Truck is a 4X4, would hate to change out ring & pinions, 2001 model) There are a few aftermarket companies that sells an 'overdrive' attachment that goes on the back of an automatic transmission (not the OEM overdrive), but last pricing I saw on this thing was at $2500! I'm too land-poor for that kind of gizmo.
J.W.

F350Lawman · Jul 10, 2003

I think with that motor the 3.73s would be better, you will also do better getting the trailer started and up hills.

I have 4.10s in my Ford PSD dually and have no problems with them. Unless you cruise on the highway at 80mph+ all the time the motor will be plenty happy to cruise along at 75mph and 3500 RPMs. My mileage doesn't differ much at 55mph and -2000 RPMs so it's OK. The truck is prettyquick of the line with the 4.10s.. Can come out of the toll booths with a pretty big trailer and run with the cars, they hate that /forums/images/graemlins/grin.gif

Guess the point is it all depends on your driving style.

Chief · Jul 11, 2003

GEP, in your case for what you may tow; definitely get the 4.10's. Yes you could get by with the 3.73's but I assume you will be towing with an automatic transmission and the GM automatics excluding the Allison lock up the torque converter in OD & D ONLY. If you get on any semblance of a hill your transmission will have to shift down to 2nd gear to maintain speed and then let the transmission roast begin! I had the 4L80E and 4.10's in my Suburban with the 5.7 liter and constantly had problems overheating the trans. fluid towing the Sea Ray. I always towed in D and never OD. I reduced the occurances by adding a Mag-Hytech transmission high capacity transmission oil pan, auxiliary trans. oil cooler,and synthetic trans. fluid but it would still get hot on steep hills. The problem was that it just could not hold 3rd gear on hills and would shift down to 2nd and out of lockup. An automatic transmission is NOT what you want for towing but if you have to make due, get the 4.10's, the heaviest duty transmission option available, an auxiliary trans. cooler, and a good synthetic fluid. I finally fixed the problem the right way like I should have and bought a Dodge Cummins HO diesel with the NV5600 6 speed manual transmission. Now there is not much I can't pull. You are pulling a pretty stout load with a 24' trailer and a car tow caddy. Good luck and be easy on the hills.

s1120 · Jul 11, 2003

I have 3:55's in my Ford van, and that is just about perfect for my use. [towing a 5000lb boat] But thats also with 15" wheels. If the truck has 16's, or tall offroad 15"'s I would say you would wan't ATLEAST the 3:73. Probably more like a 3:90, or 4:10. Remember with todays overdrives, the 4:10 are not as bad on the hiway as they were in the old days, and if you are loaded alot, you will probably get better MPG with that setup.[not lugging the truck as much]

fishman · Jul 11, 2003

3.73 with auxiliary transmission cooler should do just fine as long as you don't want to pull the load at 80 mph.

You need to look at how often you'll be pulling the load and where to. Very frequent towing of a 5500 lb load up and down mountains will be hard on any half ton automatic.

We currently have 2 trucks at work with 5.7 l engines and 3.73 rear ends. They regularly tow 3500 to 6000 lb boats a lot more often than not. We lock out overdrive anytime we get into rolling terrain. Both have over 100 k on the transmissions with no problems.

Whatever you do, don't get the 3.42 gears. You will be disappointed.

GEP · Jul 11, 2003

I won't be towing the trailer and the dolly at the same time.
Probablly towing the trailer only 3 times a year about 120 mi. one way.

Glen

cowboydoc · Jul 11, 2003

I agree with fishman. You will be fine with the 3.73. I don't think 4.10's are necessary unless all you do is haul with the truck. The 4.10's make a pretty big difference in fuel mileage to the negative. If your tranny starts hunting gears on hills just lock out overdrive.