1slow01Z71

iTrader: (36)

Like the title says, is it worth it? Im putting a new rear end in the truck and pulling the front diff isnt that big of a deal since I can work on it at my leasure.

2000 Tran Zam

iTrader: (2)

im not sure for a truck, but i hear it makes a world of difference on a f body.

bboyferal

iTrader: (9)

I'll let you know soon... I just made that same switch.

1slow01Z71

iTrader: (36)

Sweet thanks. I already got alot of weight on you guys so that helps load the turbo too. I a 6L sts gt67 setup going in right now. I have a 418 sitting on the engine stand that I need to rebuild for boost and it will have an 88mm on it then so even if it may not really benefit me right now would it later for that setup?

detroit_903

iTrader: (8)

I went from a 4:10 to a 3:50 ratio and it made a huge huge difference. With the 4:10 gears. As soon as you heard the turbo kick on you would have to shift right away. Now with those 3:50 gears you can actaully hear and feel the difference.

00ls1

iTrader: (8)

i have been thinking about it, and i think i am going to end up doing the same thing

1slow01Z71

iTrader: (36)

anyone else got anything to add

Turbo LS1 SS

iTrader: (7)

i will be doing the same swap

bboyferal

iTrader: (9)

When I went to a 12-bolt, I thought it would be cool to have a new gear set, something other than 3.42's... What a big mistake that was. I will find out exactly what the difference in spool is, and I'll be able to have more exciting 5th gear pulls.

Silverback

You’ll go fastest if you’re geared to go through the traps at the top of your 1:1 gear (probably 3rd with an auto), no matter what that does to “building boost” in first…

Big Geek

iTrader: (2)

Turbos like to be loaded. That is why you see so many turbo cars with a numerically lower gear (3.08, 3.27, 3.42, 3.55) unless one is running a Powerglide tranny or a VERY tall tire. I say make the swap so long as you don't have a large by huge camshaft and I bet you will find that the car will trap a higher MPH as it will keep it in the torque range of the camshaft. Good luck to you.

Jim C.

vanillagorilla

iTrader: (1)

You have to make sure that you don't get too caught up with choosing a high gear in a truck. Not only from the weight standpoint, but the fact that we run a lot taller of tire. With you being a 4wd, I assume you're around a 32" tall tire, and 3.42's would give you an effective gear similar to an f-body with a 26" tall tire with 2.73's. My effective gear is similar to a car with a 26" tall tire running 3.73's. It's a catch 22 though when it comes time to run slicks at the track. I learned this the hard way. I run a 31.9" tire, but now that I have the power to need slicks I can't find any that tall for a 16" rim that aren't like 18" wide. So do I run a high gear all the time like 3.23's and have it be a dog on the street so it builds boost faster and runs a better time at the track when I put a 28" slick on? 3.23's would almost make 6th gear useless for me with a 31.9" tire while obeying all speed limits.

Silverback

Yes, more engine load = more exhaust gas which amounts to faster spool… if it’s strictly a street _car_ then sure, go for it if you think you need to to get it to spool well, of course, if that’s the case you’re probably running too big a turbine housing.

If it’s a street _truck_ that actually gets used as a truck then I’d suggest you keep the gears steeper. Partially for the same reason that vanillagorilla mentioned, that you’ll be running bigger tires on it (my K1500 has 3.42’s stock and I run 33” tires on it, which mathematically works out to be about a 2.69 gear… low enough that I actually see the same gas mileage in D that I do in OD, and if it wasn’t for the 3.06 low gear it would probably suck to drive in traffic. As it is I have it rigged so that I can put the transfer case in 4LO and disable the front axle with a switch on the dash for tight maneuvering with a heavy trailer or on a hill), but more so, because these things are heavy and may be heavily loaded, both of which will make the thing very detonation prone. Boost makes that even more so, and it also makes it a bigger problem. You can usually run cheaper gas with a heavier load in the same truck with more gear. Also, when adding the turbo, you’ll want that lighter load on the drivetrain so the turbo doesn’t spool on light grades on the highway, which will hurt gas mileage, feed into that detonation problem and make it annoying to drive.

Lastly, like I already said, shallow gearing to get the turbo to spool faster at the track is a waste of time. Gear it so it finishes in at the top of it’s RPM range in the 1:1 gear and you’ll run faster then if you go with shallower gears that allow the turbo to spool faster but say, the transmission shifts into your 1:1 gear just before the finish line.

SuperZ

iTrader: (2)

I know a guy with a truck and he still has more gear in it because of the wieght but on my car going from 4.10s to 3.42s made a huge difference in a good way