Gears for tow / haul

[Gregs71]

Hey guys, just purchased a 3/4 ton V20 Silverado w/ th400. In talking with the PO, he said the original owner put 3.18 gears in the truck for better mpg?

Anyways, I purchased this 3/4 ton with the idea of towing and hauling. Now I am debating between 4.10 gears and 4.56??? It currently has 265x70x16.5 tires. Probably won't ever go bigger than 33's.

It will likely see a lot of driving at the 65-70 range.

Give me your experiences and opinions!!

Thanks,
Greg

[xtreme80]

With a TH350 and 3.73's I'm floating in the range of 3000 rpm at 65-70mph. I have a feeling the 4.10's or bigger will be a little much with only a 3 speed in it. Granted your tires are taller, but I can't expect it to help that much.

and btw, welcome to the boards

[68K20 x Drill]

unless you always have a heavy load both ways, I'd steer clear of the 4.56.

[old Rusty C10]

I use my trucks to tow and haul loads and ive used the stock rears for years and it hasnt been any problem for me.. i dont try and push the truck up hills and it doesnt go fast up hills
id see how it goes with the gears in it. For towing you have the better transmission and heavy springs but id make sure that id throw a trans cooler on there

[79Silv4x4]

The 4.10 will be a good choice with those tires. The 4.56 are a bit much IMO.

Look here for more info.

[Thumpin455]

What engine it have? Is it stock? A mildly modded 454 that makes a ton of torque around 3000 rpm will pull the gears you have. By a 'ton' I mean 400-550ftlbs. It would be tough to get a 350 to do that, or any small block for that matter.

If you have a sbc then more gear will be needed, if you have a rat, then you can make small improvements and have plenty of power and still get decent mileage. Living in California will make it more difficult and expensive to modify stuff, but it can still be done.

My 87 camper special had 4.10 gears and a 454 with Th400, it would pull anything but got around 5-8 mpg. Mostly due to needing a tune, but I doubt in stock form if it would have gotten better than 11 mpg. It has 35" tires on it and it wasnt over reving going down the road. A mild cam in the range of 224-234 duration at .050 lift along with a better intake manifold would make more power in it, and probably increase mileage. More torque down low means its easier to move the vehicle, and it will use less gas provided its tuned right.

The 87 will probably go Diesel or get an L92/LQ9 swap and become a tow rig, preferably with an electronic overdrive auto behind it. Too bad you cant do that in Nor Cal due to emissions..

What all that means is the 4.10 will work for you with the right tire, but it depends on a bunch of other things as well.

[James McClure]

Originally Posted by Gregs71

Hey guys, just purchased a 3/4 ton V20 Silverado w/ th400. In talking with the PO, he said the original owner put 3.18 gears in the truck for better mpg?

Anyways, I purchased this 3/4 ton with the idea of towing and hauling. Now I am debating between 4.10 gears and 4.56??? It currently has 265x70x16.5 tires. Probably won't ever go bigger than 33's.

It will likely see a lot of driving at the 65-70 range.

Give me your experiences and opinions!!

Thanks,
Greg

Greg: Unless your pulling a heavy trailer (over 7000#) you aren't going to need much if any gear change. Keep in mind any "range" change will force you to change the carrier assembly also (pumpkin) and if it's a locker it will COST you. By range I mean going from 2 series to 3 or 3 series to 4. DON'T use a spacer to accomplish this, you'll be sorry and out a bunch of money. My truck is a 84 K20 with a 350M engine and a HD 4 speed stick (rock crusher). The rear axel ratio is 3:08. I regularly pull a 17' utility trailer just under 7000# and have had it over 8000# with 2 1\2 skids of concrete mix with out any trouble at all. Unless you have expirence overhauling rear end's and doing the setup, don't bother, just drive it. If you do have some expirence go to the highest 3 series gears you can get (3:73 in this case) I run about 2300 RPM at 65 with 3:08. 4:10 will give you 3000 at 65 so 3:73 will fall real close to 26 to 2700. I agree with Old Rusty where trans coolers are concerned BUT, install a temp guage someplace for sure. Trans oil failure starts at 270 degrees F. I know what your thinking, "where". I don't know what to tell you there, it's going to be your choice, but anyplace you put it isn't going to be easy. This may help. Highest temp readings will be in the line going TO the cooler. Coolest temps will be in the pan. I would find a way to plumb into the cooler line as close to the trans as I could myself, but thats just my opinion. Does it have TCC?? (Transmission controled clutch) If it does AND it's working trans temp's will drop dramaticly because most of the heat is generated by the torque converter. Let us know, Jim

[Roper]

I haul horses with my 350/th350 and 4.10 gears with 285x75x16" tires. Its only a two horse trailer. Really 4.56 gears would be better. Example on the flat im okay(barely) but on any kind of grade or strong head wind im driving around in 2 gear because I need the rpms.
BTW pulling a load you will get better fuel mileage with high rpms than you will with low rpms. Like in 3rd gear I have to keep the gas floored all the time. In second gear I hardly have to give it much gas.
My truck originally had 308 rear ends. When I upgraded to one ton axles with 4.10 gears my fuel mileage greatly increased.
With a 454 motor im guessing 4.10s would be better but with a 350 I would go for the 4.56 gears. Haha With the 350 pulling a big load your not going to be able to go fast regardless of what type of gears you have in your rear end.
PS A gear spliter like gear venders overdrive would really help. Like with a 350 you just dont have any power unless you keep your rpms up.

[Gregs71]

Thanks for the help guys.

The dilemma is that I will likely be pulling a 5th wheel cattle trailer (8-10k) 2-3 times a year on relatively flat ground.

But, I'd like to buy a camping trailer (maybe a slide in) for the family too, which would mostly be used going to the Sierra Mountains. With the cost of gears, I don't want any regrets or "should of's".

The motor is a 350.

I am very surprised to hear you guys say keep the 3.18's. I always considered those a relatively high gear which is why is was considering 4.10/4.56's.

Thanks for the input & keep the advice coming.

Greg

[Pyrotechnic]

3.18 gear ? Never heard of it.

I've heard of:

2.73
3.08
3.23
3.42
3.73
4.10
4.56

At least for stock GM rears any way. I think you need to investigate further and verify what gears you have. I would go with 3.42's or 3.73's.

[Gregs71]

Ya, sounded funny to me too(maybe he meant 3.08's), but that is what the PO said. He said the truck originally had 4.10's but the original owner put in something taller to help with gas mileage years ago.

Based on what others have said on this post I am wondering how a tall gear (like the 3.08 +/-) would pull 8-10k.

Thanks,
Greg

[Roper]

Originally Posted by Gregs71

Thanks for the help guys.

The dilemma is that I will likely be pulling a 5th wheel cattle trailer (8-10k) 2-3 times a year on relatively flat ground.

But, I'd like to buy a camping trailer (maybe a slide in) for the family too, which would mostly be used going to the Sierra Mountains. With the cost of gears, I don't want any regrets or "should of's".

The motor is a 350.

I am very surprised to hear you guys say keep the 3.18's. I always considered those a relatively high gear which is why is was considering 4.10/4.56's.

Thanks for the input & keep the advice coming.

Greg

Haha I used to have a 5th wheel stock trailer. Was to much trailer for my truck. Thats why I bought the smaller two horse trailer I have now. So your going to be hauling cows? Do you know how much they weigh? I do(grin). Hahaha Like I said before go with the 4.56 gears. Even with 4.56 gears your sure not going to be cruising down the highway like the modern diesel crowd does.
Also your fuel mileage is going to suck big time pulling a stock trailer regardless of you gear ratio.
Honestly if your going to be pulling cows you might as well forget it with this truck and get a Cummins. Fuel bill will kill you. Im not running junk either. My truck has a new crate motor, new edelbrock carb, etc.

[Roper]

PS Factory one tons where only availible from the factory with either 4.10 or 4.56 gears for a reason. Also back in the 73 to 87 years big stock trailers where not common. Back in the 70s a bumper pull two horse trailer was considered a big load for a one ton truck.
People moved cattle with 3 ton or bigger trucks. Example they had stock racks on the back of the truck.
These trucks were never designed to be pulling big stock trailers like todays diesels are. Plus gas was what? 50 cents a gallon 30 years ago.

[spudz]

with 33s...u need 3:42-3:73, 35s= 4:10-4:56, 38s....4:46-4:88s... The higher gear feeling like it has less power and tourqe but will get the job done and spin less RPMS on the hwy.. But the lower gear will have be the manly way to go...lol I mean hell new trucks even though they have an overdrive come stock with 3:73s. mostly.

[cochino12]

go with the 4:10

[68K20 x Drill]

Well, with 4,10sband 35" tires, I turn 3000 RPM at 75, 2200 at 55MPH.
Towing a truck on a trailer, I really feel it in the hills, but can go as fast as I dare on the flat. It sounds like you have maybe 7~8K loaded? pretty similar.
I had 4.56's, but I didn't like shifting to second halfway through intersections.


Your current tires with 4.10s puts you at 3000 RPM at 68 MPH, or 2450 RPM at 55MPH

4.56 gears will give you 61 MPH @ 3000, 55MPH @ 2700

There is a calculator here;
(CLICKY)


EDIT; The 1995 will have a much more expensive transmission, and a better radio.

[Roper]

The 5th wheel trailer if I remember right was only 16 feet and rated for 12,000lbs. I used to haul 2 horses in the back and it had living quarters in the front.
I live in the foothills of SW Alberta. The worst hills are right on the ranch here. Around the ranch I drive in 4x4 low range because of the hills. Once you get off the ranch its basically flat with hills every now and again. But whats as bad as the hills is the wind. The wind blows here most of the time really hard. Example a 45mph wind is just a breeze. We can get wind storms here when the wind blows hard enough to move 1200lbs round bales of hay.
I used to tow all the time when gas was 50 cents a liter but as gas goes up I dont tow as much. Example gas right now is currently about $1 a liter or $4 a gallon. When you hook up to a stock trailer your gas milieage goes all to pieces regardless if you have a new Dodge Hemi or an old school truck like we drive. Example with my truck my fuel mileage would drop atleast in half pulling a trailer. My speedometer is off so I cant tell you my exact mileage. But say for me to leave here and go to Fort Macleod. Well without a trailer it takes about an hour and a half round trip. Hauling 2 horses it would take atleast 2 hours for the same trip and I would burn a tank of gas (15 to 20 gallons)doing it. With the 308 gears my fuel mileage was much worse. Example I bought a horse up in Caroline which was a 6 hour round trip. It took 5 tanks of fuel to make the trip and it was on good roads to.Even with a new Cummins your mileage isnt going to be great, but its going to be way better than any gas truck. Example my friends cummins averages about 13mpg according to his computer and he pulls a 24 foot stock trailer about half the time.
With my current 350 motor, 3 speed auto and 4.10 gears its a good rig for hauling a two horse bumper pull occasionaly. Example any kind of a hill or in windy conditions im in second gear. On the flat or on a reasonable calm day I have good power and have no trouble driving in third. But for hauling I would much rather have 456 gears. BTW 456 gears are not all that low. One friend of mine has a 70s Dodge one ton and that came from the factory with 4.88 gears. A neighouring outfit has a whole fleet of 60s era Dodge Fargo 4x4s that they use for daily drivers (on the ranch)and I dont know the gearing but they are extremely low. Example these are one tons with 440 motors in them.
Truck campers
I used to have one years ago on a 88 Ford with a 5L, 5 speed and 3.55 gears. Truck campers catch a lot of wind. That truck IMO wasnt big enough to haul that camper!
Anyway for the loads and driving conditions you describe im sure you could make out with 410 gears but I would still rather have the 456 rear end if it was me.
If you want to be able to fly down the highway empty then get a overdrive transmission or another truck that your not going to use for hauling.
See there is no cheap way of hauling a stock trailer. Get your old gas truck set up for hauling and then its not all that great for a daily driver. The higher you gear it say for use as a daily driver the more its going to suck as a hauler. Go out and buy a new diesel and then you will have a great daily driver and a hauler but a new diesel costs a fortune. Haha I have put a lot of thought into this over the years. If any of you know of a cheap truck thats a good daily driver and thats good for hauling horses , please let me know about it.
Anyway at first when you where talking about hauling a 5th wheel stock trailer I visioned a 20 foot or bigger trailer packed with cattle. Not just a few steers going to the feedlot or to the local auction mart thats a half hour drive down the road.
About the 95 doing the job so why cant the 87. Im not up on the new trucks but if the 96 is only pulling light loads then im sure it could do the job. Also wouldnt a 95 have the higher output vortec engine? Wouldnt it have an overdrive transmission? If it had an overdrive transmission with low gears then that would really help it.
You know years and years ago I used to drive a couple of gas tandem gravel trucks. They had Chevy 366 and 427 gas engines. The little gassers could haul the weight because both trucks had a 5 speed transmission with a 4 speed auxilery transmission. In other words both trucks had 20 gears. It was the gearing that enabled them to haul the weight. Without the gears they would have been no better than our pick up trucks.

[shrtbx]

This is a great thread answers alot of questions for me as well. Im curious though. While i was reading through the archives about rear end ratios i saw that one or two people said they got better gas mileage when they swapped out there 3:08 gears for 3:73s. I always thought that no matter what you suffered when you went with higher ratios. Only reason i could come up with is that with 3:73s you dont have to stay on the gas as much to keep up your speed on the HWY.(or is that totally off the mark)

[Gregs71]

Shrtbx,

Changing the gears has a lot to do with "how hard" the motor is working at a given speed. If the gears are set properly with the motor for a certain type of driving, then the motor isn't over working and you get ideal mileage.

Roper,

Ya, of course I'd love to have a crew-cab duramax / allison set up. BUT, cost of the truck, I could buy 15 years worth of fuel if not more. I know this isn't an ideal set up, but its close enough (at least for the pocket book).

It sounds like 4.10's would about right. 4.56 would be nice on those steep mountain roads with a camping trailer / slide-in. But I don't think I can live with 3000 rpm 61 mph (thanks for the math 68K20 x Drill).

Greg

[68K20 x Drill]

How hard the motor is working is a funny thing. If you get the chance to drive a diesel with an EGT gauge, watch it as you drive. it's a direct indication of engine load, and it still surprises me sometimes where it is best to shift gears. It has a lot to do with where your cam makes peak efficiency.

Unless you really go crazy, most camp trailers are way less of a load thatn your stock trailer, so it will be less of an issue.
I got a '67 Coleman pop top trailer that weighs about 800LB. I put everything for 4 people to go to Burningman for a week in it and my Suburban, probably another 1000LB, maybe even more. I figure my turbo 6.2 diesel is pretty equivalent in power to a good small block, and with 3.73's I was able to maintain 55MPH(top of 2nd gear sometimes) from Sacramento to Reno which you probably know is a fairly wicked hill. On the flat , 75 was no problem. I still got about 15MPG for the trip, my small block won't do that unloaded.

A thought I just had is since you don't tow that frequently, get a set of cheap wheels with small heavy duty tires, and put those on when trailering. Get a nice set of 32s for driving around the rest of the time. If you patiently watch Craigslist like a hawk, you can get amazing deals. I got myself a set of cherry WELD alloys with 60% remaining on some BigO tires for $300, then got hundred back selling my old wheels.

[shrtbx]

Im talking regular highway cruising Without towing. As far as hauling with a trailer I would go with 4:10s at the most. Of coarse that all depends on what you are consistently hauling. In reality you just want enough torque to get onto the hwy and merge on safetly after that you shouldnt really be trying to pass anyone thats going a decent speed. You are going to eat up gas regardless if you are towing something.

[Roper]

Shortbox

I dont see how its possible to get better fuel mileage with 308 gears if your hauling a load. Like I said my truck originally had 308 gears, then I swaped in one ton axles that have 4.10s and my mileage definately got better. But mostly when I use my truck im hauling something.
Maybe the people who got better mileage with the 308 gears who dont haul tend to cruise down the highway 80mph? See im mostly on gravel roads and im never really in a hurry to go anywhere these days.

Greg
Thats just it, about a new diesel truck. You would have to be hauling a trailer a lot of miles to ever justify the cost of one.

[shrtbx]

I didnt say you could get better gas mileage by having 3:08s and hauling a load. I actually stated 4:10s would be the way to go.

[Thumpin455]

With a 350 pulling you will be working that little thing to death no matter what gear you run. When you are towing, especially on grades, you want your cruise rpm to be just over your torque peak, that way you have some power left a bit lower for hills. If you are only working with 250ftlbs at the flywheel it wont matter what gears you run, it will be a pooch with any of them.

If you are serious about a pulling rig based on your old truck you need to change more than just the gears. More torque with less throttle angle will pull better and not burn fuel at a kill more dinosaurs rate. How do you get more torque? Make your engine more efficient for one, make it bigger for another. The 80s engines are weak suck in stock form for the most part, but upgrades are available and you can retain smog legality to an extent.

Using your 350 as a base I would suggest a few changes in addition to a set of 3.73 gears with 33" tires. First freshen the bottom end, bore it .030, use quality rings and gaskets, dont go gapless with the rings. Have it balanced because that will help with longevity and they also seem to run much better when balanced.

You can pick up a new set of Vortec heads for the small block for around $400-$500 ready to bolt on. You can get them drilled for your 87 intake, that way you can use the TBI and keep it looking smog legal. No Holley for you in California. They are the best factory head you can find regarding flow, combustion chamber, and availability. its tough finding a set in a junkyard that isnt cracked, so just pony up for a new set. The stock springs are good for around .450 lift, but that works since you dont want a huge cam in there.

Speaking of the cam, a Comp XE262 will give you plenty of power and it wont lope at idle. Alternatively you can run an inexpensive Summit Racing cam with 224/228 degrees duration at .050 lift. It might be a bit difficult to get that to pass smog though, and those are the biggest cams you will want to run anyway. More duration will move the power band up in RPM and you will lose torque under 3000 rpm with a 350.

If you can find some smog legal headers that fit your truck, then that would be advisable too. Otherwise run the stock stuff, it wont hurt the bottom end at all. You wont be spinning it to 5000-6500 rpm anyway.

Next up is the trans, the Th350 will work for a while, but a Th400 would be better. A 700R4 would still work, although you shouldnt tow in OD with one. The 700 will cost more than a TH350/400 to build and install, but the OD when you arent towing will be nice. I can get you a list of upgrades to use in a 700 if you like. Stay away from the cheap tiny coolers and get one that has some surface area. A quality converter is a must, a stock stall speed and a tight coupling will limit heat generated by slippage. You could use an L88 Corvette style converter, they stall around 1900-2200, are full size converters, and can be picked up at any trans shop. They are tight for the stall speed and use a full size 13" case. Otherwise just use a stock stall speed. Th350s and Th400s use the same converter, the 700 is different and will not work. There was a Th350C that had a lock up converter but they were problematic and you really dont want one.

The high dollar alternative is a 4L80E, for about $3k you can have a bulletproof trans that will take any abuse you throw at it, with an overdrive. Its computer controlled so it needs a controller to use one. There have been threads about them here if you are interested. The 4L80E is a descendant of the TH400 but with an overdrive and electronic valvebody.

A lock up converter simply has a clutch plate inside it that connects the input shaft to the engine with no slippage when its applied. This cuts down the heat generated by the fluid shearing inside the converter, it also picks up some mileage in addition to reducing heat. All OD auto transmissions since the 80s are lock up converters from the factory.

Now if you move up to a 454 with a mild cam like the XE262 or even the XE274 it will make enough torque to pull almost anything. its relatively easy to make 500ftlbs with a rat or any large displacement engine (455 Buick, Olds, Pontiac), the problem with the alternative engines is smog, not cost. No matter what anyone tells you, a rat is pricey to build and actually if done right the BOP 455 can be built for much less and make the same or more power. You just cant stuff one in there and stay legal. You will also need to move up to a TH400 at the very least, yes a manual is nice but a clutch can burn up as easily as an auto.

If you want a really nice but expensive upgrade to your drivetrain, a Duramax swap from a newer truck would be perfect. It wont be cheap but that engine and trans will pull anything and get decent mileage doing it. We pull 34ft boats, and two car trailers with 3/4 and 1 ton 4x4 Duramax trucks, no matter what we put behind them we rarely see under 18mpg and usually its around 22mpg. Pulling a loaded 8000lb car trailer through the hills around Atlanta the 3/4 ton 4x4 didnt have to kick down very often. The new 6 speed 07 is even nicer to pull with. That is going to be expensive to swap in though, at least $5k if you can find the parts cheap enough and do all the work yourself.

The basics are more torque on the bottom, easier towing and better mileage all the time.

[Thumpin455]

Almost forgot, you could also swap in an L92/LQ9 6.0L, actually that wouldnt be terrible expensive considering what you get. I have read about some junkyards selling those engines for around $1000-$1500, you will need a computer for it but you can get aftermarket stand alone systems. HOTROD did an article on them a while back, they got 500hp/tq really easy from one, just a mild cam and a set of headers. Now that would end your towing problems right quick.