Gearing?

[Dalaigh]

Ok guys, I've got a question that is no-bout ask all the time, but I gotta ask again.
I'm looking to re-gear my truck, the thing is I'm not entirely sure what direction I'm going yet.
Right now the truck has a 6" lift and 35's and either 3.23 gears like the vin states, or 3.42 like the PO said. Either way it doesn't matter which it is because either way, they need to go, the truck sucks on highway, has no power, and sucks to much gas even for a lifted, carbed, hopped up truck.

The thing is, I'm thinking about taking some lift out and going down to 33's, because I use this truck everyday and it would be more practical alittle lower.

But, on the other hand I like the way it sits right now, well, I'd like to level it out abit, got the ugly cali lean right now. Other then that it looks great.

So on to the question. What gears do you guys think would be best for each situation?

I'd like to improve the trucks fuel economy (I know it won't be much, but anything is an improvement), give it some more get-up and go, and get the rpms in a better range on the highway (right know they are around 2500rpm at 100kms, I'd like to get it around 2000rpms at 100kms )

I'm thinking 3.73 or 4.11's for the 33's set up
and 4.11 or 4.56 for the 35's
Any help would be great.

Oh, and not sure if it matters but I've got a th400/np205 with a mildly built 350

[71blazerdetroit]

Your 3.23 gear is terrible for the current setup for sure.

Here is a gear calculator for any combination you want. http://www.grimmjeeper.com/gears.html

[Altec]

Are you sure your speedo is correct? With The gears, tires, and transmission you have (No OD) would result in 1922RPM at 100kph. For it to be 2500RPM you would have to have 4.11 gears. Which is about ideal for your setup.

If you want to get it down to 2000RPM you need 3.42 gears with 35" tires. Or 3.08 with 33" tires.

Either way, if you do turn out to have 4.11 gears, I would leave them. 35" tires, with the mild first gear of the 400 would be a real pig to get moving with anything smaller. Maybe a 700R4 swap is in your future? It is a OD transmission, and first gear has roughly .6 more reduction. Which would be more like having 4.56 gears (Well, more like 4.69, but nobody has that gear option...) instead of 4.11 gears. Not to mention the 30% overdrive. Which would bring your RPMs down to 1712RPM for 100KPH.

[Dalaigh]

No, I know my Speedo is off, I'm guessing thats what it was at, I don't even have a tach, So I could be wrong on all those. I just now that My trucks rpms a to low on the highway, and after reading my original post I realize I put the figures in backwards, I want to be at 2500 and I'm under 2000, I want the truck in it's power band, right now the rpms are too low and the performance and fuel economy are suffering.

I know the 700r4 is an Overdrive, but I have no intention of swaping out my th400 for a weaker transmission, I do tow with this truck. I should've mentioned that too.

[Altec]

Yeah, I was having a hard time following what you were saying. Only thing I could do was follow the numbers lol.

Being a tow pig makes a big difference. If it was mine I'd go with 4.56 gears. It'll put it in the 2700RPM range, and give you the grunt for towing.

edit,

Oh, if you are looking for a tach, I can point to some low buck options. If you know your gears, you don't even need a speedo if you can read the tach.

[Dalaigh]

Yeah I have a tach, just not installed in the truck. I have all new autometer gauges to install in the truck. But, I'm still building my workshop, so I have nowhere to install anything.
If I end up going to 33's will my rpms be at 2500 with 4.11's?

[lycominghunter]

What equation are you using to figure this out? I tried to figure it out the other night and wasn't able to relate rpm to mph/kph. Thanks alot!

I actually have a 6" lift and 35's on my k20. I'm not 100% sure what my rears are, and Ive got a sm465, but 2500 would be a good rpm for towing at 100 kph (JMHO). My truck isn't going to be towing or hauling too much, so I'm trying to figure drop my rpm's down for on the highway.

[Mr. 250r]

why not a 4l80e out of lets say a 91 suburban like mine in strength wise its a th400 with OD i love mine it pulls my 7in lifted, 38.5in tires fine on the highway

[Dalaigh]

Originally Posted by Mr. 250r

why not a 4l80e out of lets say a 91 suburban like mine in strength wise its a th400 with OD i love mine it pulls my 7in lifted, 38.5in tires fine on the highway

I have a 4l80e in my other truck, but I have a perfectly good, recently rebuilt th400, and I don't wanna deal with swappin over the computer and fabbin mounts for sensors to run he 4l80e on a carbed truck. Not to mention swapping the trans crossmember, shortening and lengthening the drive shafts, because it's longer then the th400. It's easier to just put new gears in, gonna need them either way. Eventually I'd like to swap in an NV4500, and do away with the auto's all together.

[Mr. 250r]

you make very valid points lol i wouldn't do all that either but im not a fan of driving a stick daily unless its a diesel and a 6spd for some reason
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