Haven't posted in awhile
 

Hi All,

I sold my last square body about 3 years ago and haven't been around the website much. Mostly because my oldest car now is my 1991 Chevy Van. Haha.

But I thought I would share my 2006 GMC 4.8L 4x4 with (I think 3:42 gears) that is my daily driver. I've never really posted about it because I mostly use it to haul my camper. Which brings me to the reason for this post.

Can anyone tell me what are the best choices I could make as far as making this thing tow better? I'm sure most of you will say "drop in 5.3", but that is not an option for me right now. Should I re-gear the axles to 3:73? I figure that's a couple grand at least. Would I have to change anything with the computer?

I've read about Black Bear Performance and maybe I could have them re-program my computer for more performance? Thoughts?

Anyways, here are some pics so you can see what I am working with. Truck has 138,xxx original miles. I believe I am the 2nd owner and truck extremely well cared for by first owner.

Thanks!

Re: Haven't posted in awhile
 

I guess I should mention this is not a mid-west truck. I just moved to Chicago from Portland last year and brought it with me. I hate driving it in the snow around here because of the salt. There is zero rust on the truck and I was hoping to keep it that way, but I don't think I'll be that lucky.

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Crap! I posted in the wrong board! Can an administrator please move to 99-06 for me? Sorry! I'm rusty....

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Got it for ya Cort. Glad to see you back on again. I would think going with gears first would be your best bet. The 4.8 can handle the load.

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Thanks Bill! Yeah I was thinking gears might be the best investment too.

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Give it a really good oil spray underneath and that should help to keep the rust away

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Yeah I am a big fan of Boeshield T-9. I use it on boats a lot and it holds up very well. I try to spray it in the nooks and crannies of the door drains and fenders drains. We'll see how she holds up!

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It's a 4x4 so you have twice the gears to deal with.
You'll have to modify the gearing in the ABS Computer if it's an allowed gearing and the PCM. You can likely change the gearing with a Tech 2 if 3.73:1 was an option on that computer.

I think I'd change the engine oil cooler lines while the front axle is down. Access will be much easier. If you have an oil pan leak I'd get that at the same time.

Eric O from South Main Auto did a YouTube video on installing new bearings in a T800 front axle while re-using the gears. They're a little more fiddly than a straight axle but not impossibly obnoxious. New gears means you get to measure pinion depth and probably use two or three crush sleeves in the process... and I bet setting the end play is a real fun job too.


You can bump up the numerical gear ratio slightly by using smaller OD tires but this is a truck you want to use as a truck so lowering it with smaller tires isn't really a good option.

Re: Haven't posted in awhile
 

Thanks Hatzie,

I didn't even think about the computer issues. But I'll be having a shop perform the gear replacements on both axles and I'll ask them if they're aware of the computer changes needed. If they look at me with the deer in the headlights look, I'll go to another shop. Haha.

No oil leaks on this girl. At least not yet....

Re: Haven't posted in awhile
 

If you have a Tech2 or MDI with Tech2Win you can do the ABS re-coding... assuming GM has an option for 3.73:1 in the selection table.
You need a package like HP Tuners or something of similar capability to deal with the PCM.

If you have larger than stock tires you need to deal with that in both computers as well.

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OK sounds good. I believe tires are stock size. I only have a leveling kit installed on the truck, so couldn't go much bigger anyways.

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That's a super nice pickup you have there. My opinion would be to not drive it in the winter, keep it clean and rust free. Buy another pickup for hauling and work. But I know that's not always an option for us.

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Being in the rustbelt now, you should have no problem finding someone parting out a truck with 3.73 gearing and grabbing the front and rear diffs from them. I have a couple here now but wrong coast.

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Yeah, great idea! I'm still getting used to the area and haven't even looked for salvage yards yet.

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3.73 is a common optional gear on the 2500s.
How common were 3.73 gears on the 1500 trucks?

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I'm not sure at all. These days I most likely won't have the time to go to junkyards and/or perform the swap myself anyways. I'm just going to have a shop perform the install. I need to find a reputable 4x4 or drivetrain shop in the west chicagoland area that I can trust to do it right. I usually don't let shops touch my vehicles....

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3.73 was very common on 1500's. I have 4 parts trucks here now all with 3.73.

Look for code GT4 on the SPID in the glovebox to find it.

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The older rigs used 3.54 & 3.08 gears more often than not. It seems the 4.10 gears on the 3/4 ton trucks are still the most common gearset.

GT4 on the SPID tag is a good jumping off point. I'd still verify by pulling the cover on the rear and get the front axle from the same truck.

If you want to be nice to the next guy cross the gear ratio out with black sharpie and write GT4 on the SPID.