37s and 3:73s

[Ehall8702]

Have 35s in my truck right now and it's got plenty power , can easily hit brakes and tap gas and it'll spin rears no hesitation. Got 22mpg with my 33s , haven't taken a trip yet with the 35s and trans is jacked right now ( only 1&3rd) haven't out new trans in yet. Have 37s coming on a trade and wondering how my truck will do with em. Only mods right now r deleted the cats, added x pipe in thier place, ground off the baffle on my throttle plate and removed the vortec box on the intake tube. Have a CAI on the way and will be replacing the stock muffler with some magnaflows ( maybe 2 into tailpipe or just a single after a y pipe not sure yet, depends on how loud it is cause I don't want a super loud truck), going to do the 0411 ecm swap soon with a tune from black bear performance in the near future too. Down the road will get a cam/lifter/rocker setup and maybe headers and duals too. I'm just wondering if I should be saving up for a 4:55( or whatever gearing is applicable for the obs chevs) gear swap instead. I'm amazed at the power I still have with the 35s, tow my camper no issues , roll in 3rd gear at 65/70 at about 1500-1600rpm , I'd imagine about 1200 in OD when I put new trans in.

 

[df2x4]

I would definitely re-gear if you're going to run a tire that large. On another unrelated note...

Have a CAI on the way

I hope it's a Volant, otherwise you're going to have higher intake air temperatures than the factory setup. They're the only ones that make a sealed airbox that draws fresh air from the factory hole in the front fender, all the rest like K&N are an open box design and draw warm engine compartment air. I actually bought a K&N FIPK for my red truck and later removed it in favor of the factory intake due to the consistent difference in IATs. Not to mention the oiled gauze K&N filter was over-oiled straight out of the box and fouled my MAF sensor.

 

[Ehall8702]

It's not a volant, it's an eBay cheapie but already had the idea to Fab a sealed box to pull only cold air . I have a break and a decent mig setup so it'll be a relatively easy deal. I went through the same thing on my 87 mustang, iat temps were too high and was affecting the air)fuel ratios. Awesome you brought it up tho, cause most ppl don't know any better and eBay will sell ya sum junk with the promise of "xx" hp gains lol

 

[df2x4]

Gotcha. It's not just eBay parts that pull that gimmick, K&N actually have "dyno sheets" on their website for the FIPKs claiming 5-7HP on a stock 350 if I remember correctly. I've always speculated that they probably did a full tune up on the test vehicle in addition to swapping the intakes to get the before and after on those.

 

[Ehall8702]

How bad u think it'll be with a full tune and my few mods with stock gearing? I can't get a good idea with the 35s cause I didn't have em long and the trans **** out on me. I drive about 10 miles a day with it rite now so I really don't get to run the highway with hills and stuff and I only have 3rd gear at the moment ( my trip is just at 1 miles to work and I come home for lunch so all about 8-10 miles a day). The 33s it never really down shifted much even in our hilly ass area so I'd imagine wouldn't make much difference with 35s but 37s r quite a bit bigger than 33s . I may have to set aside the cam stuff and do a gear swap instead. I'm waiting on my body lift before I can put the 37s under it tho, have 3" suspension now and 35s only rub at full lock so once I get my '14 gmv Denali 20s back on the 37s shouldn't rub too much.

 

[df2x4]

I'm not the one to ask for personal experience, both of my trucks still run factory wheels and tires. I'd imagine the effects of switching to 37" tires would be pretty noticeable with 3.73s though. I think most people here running 35"s or larger recommend 4.56s. I'm sure someone else will chime in.

 

[Supercharged111]

I put 33s on mine with 3.73s and hated life. I can't imagine 37s on that gear.

 

[Hipster]

I have 285's(32.8 inches?) with 3.73 and would also say it's barely adequate.

Engines need to run at their cruise rpm. Lugging along at 1200-1500 rpm is hard on engines and transmissions and it's actually less fuel efficient then running at 2200-2500 where the engine is "on the cam" and producing much more torque. Especially if pulling a load. A bigger cam that moves the torque curve further up the rpm range doesn't fit the plan. Do gears first. Lugging is the destroyer of engines and transmissions.

If you think it has plenty of power now re-gear it. You'll be amazed and might decide not to do the other stuff.

I'm not buying 22 mpg's rolling around in an under-geared truck. Bigger heavier tires, more rolling resistance, more air under the truck blah, blah, blah. I don't think many or any of us could come close to making that claim.

 

[b454rat]

I second the mileage. Stock they didn't get that high. I had a 99 Tahoe that was lifted a total of 9". had 35s when I got it, with 3.73s. Wasn't horrible, but wasn't great either. Motor ran strong, tranny would snap your head back. I put 38s on it, and couldn't use OD inless going down hill bout 90. Regear to 4.56s, you will have more pulling power, not to mention save your tranny.

 

[Ehall8702]

I put 33s on mine with 3.73s and hated life. I can't imagine 37s on that gear.

I have 285's(32.8 inches?) with 3.73 and would also say it's barely adequate.

Engines need to run at their cruise rpm. Lugging along at 1200-1500 rpm is hard on engines and transmissions and it's actually less fuel efficient then running at 2200-2500 where the engine is "on the cam" and producing much more torque. Especially if pulling a load. A bigger cam that moves the torque curve further up the rpm range doesn't fit the plan. Do gears first. Lugging is the destroyer of engines and transmissions.

If you think it has plenty of power now re-gear it. You'll be amazed and might decide not to do the other stuff.

I'm not buying 22 mpg's rolling around in an under-geared truck. Bigger heavier tires, more rolling resistance, more air under the truck blah, blah, blah. I don't think many or any of us could come close to making that claim.

I didn't believe it either , why I did the math a handfull of times just because I figured there was no way that was right. Now I left out that was straight interstate riding from the UP to Rockford Illinois and then back. I don't keep track around town or on my daily travels as I honestly don't care about those numbers. As for the power issue, I could hardly pass a car going uphill with the stock tires on it (265/75r16 roughly a 31x10.50) untill I pulled my throttle plate and ground off the aluminum "baffle" on it, removes the vortec box at the same time so idk which made the difference but man did it make a HUGE difference. I stand by my highway claim of 22 mpg tho, a buddy of mine has a standard can long box with 3:42 on 305s ( 33s) and claims 21-22mpg. We don't really have anything but long open roads here with 55+ mph speed limits, not alot of "town" driving so that may help the mileage numbers some. I got two sets of rims so I'll put the 37s on and see what it feels like and if it's a dog they will come off and wait till I get sum gears for it. The option of SAS is there to but all I really have access to is 3/4 and 1 ton axles and damn sure don't think that'd be good daily driver setup.