Build thread - 3.08 to 3.42 front and rear gear change

Got it to my local tuner today to make the axle ratio adjustment. He uses TunerCats and there ended up being 100+ parameters changed. I thought shift points were just based on RPM, but actually they're based on mph corresponding to throttle position, hence the need for many changes. It drove OK on the way to his place, but definitely better on the way home! Very glad to have my rig back after almost a month being down.

This was part three of my plan to convert my soccer-mom, grocery-getter Tahoe to a more tow-capable rig.

1. Converted single speed t-case to 2-speed.
2. Added heavy duty cooling, e.g. factory-style aux trans and engine oil coolers.
3. Converted 3.08 AR to 3.42, front and rear.

Essentially I think I've added RPOs NQH, K5L, and GU6. (Please chime in if there's anything more I need to do!) Why didn't I just look harder for one with those options?? Good question. This one came along when I was looking after my '09 was rolled. It's in great shape, had new tires, and the price was unbeatable: I paid $7500 for it when similar mileage and condition at a dealer would have been in the neighborhood of $12K.

Next on the list:

1. Full flush on the brake system. I did some today - replaced fluid in M/C and got the system bled enough to have a firm pedal, but my Holt power vacuum bleeder just doesn't seem to be able to pull fluid through the back brakes. It pulls great through the front though, so I at least flushed out the front of the system. I have to decide if I'm brave enough to try the bleeding procedure with the Tech 2.

2. Need to flush the P/S system, too.

3. Install a decent quality brake controller.

DaveO9 said:

Got it to my local tuner today to make the axle ratio adjustment. He uses TunerCats and there ended up being 100+ parameters changed. I thought shift points were just based on RPM, but actually they're based on mph corresponding to throttle position, hence the need for many changes. It drove OK on the way to his place, but definitely better on the way home! Very glad to have my rig back after almost a month being down.

This was part three of my plan to convert my soccer-mom, grocery-getter Tahoe to a more tow-capable rig.

1. Converted single speed t-case to 2-speed.
2. Added heavy duty cooling, e.g. factory-style aux trans and engine oil coolers.
3. Converted 3.08 AR to 3.42, front and rear.

Essentially I think I've added RPOs NQH, K5L, and GU6. (Please chime in if there's anything more I need to do!) Why didn't I just look harder for one with those options?? Good question. This one came along when I was looking after my '09 was rolled. It's in great shape, had new tires, and the price was unbeatable: I paid $7500 for it when similar mileage and condition at a dealer would have been in the neighborhood of $12K.

Next on the list:

1. Full flush on the brake system. I did some today - replaced fluid in M/C and got the system bled enough to have a firm pedal, but my Holt power vacuum bleeder just doesn't seem to be able to pull fluid through the back brakes. It pulls great through the front though, so I at least flushed out the front of the system. I have to decide if I'm brave enough to try the bleeding procedure with the Tech 2.

2. Need to flush the P/S system, too.

3. Install a decent quality brake controller.

Click to expand...

Awesome! Congrats!

FWIW, I have successfully bled all of the brakes on both of my GMT900's using the old-fashioned tube in a cup method, with no problems. Just had to have a helper to push the brake pedal.

Driving comparison after you get enough time behind the wheel please!

x2 what Geotrash/Dave said,
or
I have teloscoping stick like tools to hold the pedal down (no second person necessay),
or
gravity, its slow and easy and a 1 person job.
also
a couple of times each yr, on a rainy day, I take all my vehicles out (I live in the country) and do a few panic stops so as to pump some fresh brake fluid thru the abs hydraulic control module.

DaveO9 said:

Got it resolved! Nice and simple - pass side rear sensor was unplugged! Must have happened at some during rear end changeover. Good thing it doesn’t seem to have any problems. Been driving around all day, no issues or warnings.

It was throwing a C0050 code - circuit issue on rear pass sensor. Chased the wire up on top of frame, found the unplugged connector.

Click to expand...

My passenger side WSS has done this twice since my swap!

Now I'm wondering if it has something to do with a different angle on a bracket or maybe the WSS attachment points on the 14 bolt are clocked at a slightly different time than the 10 bolt? possibly causing the wire to be pulled? possibly during suspension flex?

edit: Just to confirm mine pulled apart at the first connection, not out of the axle....yours same?

DaveO9 said:

Essentially I think I've added RPOs NQH, K5L, and GU6.

Click to expand...

and: AXN

DaveO9 said:

(Please chime in if there's anything more I need to do!)

Click to expand...

In order of importance- Non-Engine=
1. Hook up to a trailer and press send.... lol But seriously go feel it out, if you're not towing 7500# or more from Knoxville to Pittsburgh and back everyday, I think you'll be very happy with what you've done
2. Brakes(forgive me if already addressed?)
3. Torque converter
4. Torque converter
5. Torque converter
Engine=
1. Torque converter
2. Truck Norris cam(to best my research it gives most bottom end torque of cam options)
3. Small turbo= 67ish mm pushing about 6psi
4. Stroker
Of all these (brakes for safety-unless addressed) the torque converter and a trans tune to maximize it will be most beneficial

DaveO9 said:

Why didn't I just look harder for one with those options??

Click to expand...

imho, deja-vu is a sign reassuring that you are where you're supposed to be in life at that exact moment. imho, we're shown signs like this on a regular basis.....but and your eyes and your mind must be open to see them. This one really resonated with me yesterday. Went back and listened to it 3 times as day wore on.....but I didn't see what I was supposed to do with it until just now (from 14:05 - 15:30) :
Also, because you wanted/needed to build some trust with and learn some things about your tow rig; learn how to navigate the "aftermarket"; and learn that @swathdiver can find any part anywhere any day of the week! ...and most importantly: you empowered yourself to be less reliant on others! Gained confidence in your ability to overcome adversity and unforeseen issues. And added value to your personal and financial portfolio! [ $7500 truck worth $14k now ]

DaveO9 said:

I have to decide if I'm brave enough to try the bleeding procedure with the Tech 2.

Click to expand...

+ 1 on @donjetman solution. I use a 24" wood clamp with the roll pin removed so can turn clamps around and make a spreader. If you pump then hold pedal down w/foot, then place the spreader on brake pedal and pump the other end far enough into the seat cushion, when you open bleeder screw the cushion rebound will give you just enough of a pump on the pedal to do the job. * * IF you're using the Tech 2(or other bi-directional diag tool) to fluctuate the diaphragms in the ABS box, AS you open the bleeder * *

DaveO9 said:

Install a decent quality brake controller

Click to expand...

Pretty sure I'm going to get a lower dash panel w/factory controller on it from salvage, wire it in and make sure it's activate with Tech 2(if it ever get here). That means I have a never used Tekonsha P3 for sale, with GM wiring plug

5StarCustmSolutns said:

Pretty sure I'm going to get a lower dash panel w/factory controller on it from salvage, wire it in and make sure it's activate with Tech 2(if it ever get here). That means I have a never used Tekonsha P3 for sale, with GM wiring plug

Click to expand...

Dan, you can't add the factory controller without taking your truck apart, replacing the wiring harness and a bunch of modules and of course the programming. It truly is "integrated".

Geotrash said:

Awesome! Congrats!

FWIW, I have successfully bled all of the brakes on both of my GMT900's using the old-fashioned tube in a cup method, with no problems. Just had to have a helper to push the brake pedal.

Click to expand...

donjetman said:

x2 what Geotrash/Dave said,
or
I have teloscoping stick like tools to hold the pedal down (no second person necessay),
or
gravity, its slow and easy and a 1 person job.
also
a couple of times each yr, on a rainy day, I take all my vehicles out (I live in the country) and do a few panic stops so as to pump some fresh brake fluid thru the abs hydraulic control module.

Click to expand...

Thanks guys. Yeah the good old fashioned 2-person brake bleed is next on the agenda. I just ran out of time based on when I needed to get to the tuner. (And no one else was home at the time) maybe I’ll try the rod against the brake pedal trick but probably will just my wife or one of the kids help. I did try the gravity bleed method to no avail. (Actually one of my preferred methods on other cars) they started dripping right away, but I think it just drained the calipers and then stopped. Let them sit for like an hour - nothing.

5StarCustmSolutns said:

My passenger side WSS has done this twice since my swap!

Now I'm wondering if it has something to do with a different angle on a bracket or maybe the WSS attachment points on the 14 bolt are clocked at a slightly different time than the 10 bolt? possibly causing the wire to be pulled? possibly during suspension flex?

edit: Just to confirm mine pulled apart at the first connection, not out of the axle....yours same?

Click to expand...

Yep first connection up on top of the frame. I will definitely keep an eye on it, thanks for letting me know.

5StarCustmSolutns said:

and: AXN

In order of importance- Non-Engine=
1. Hook up to a trailer and press send.... lol But seriously go feel it out, if you're not towing 7500# or more from Knoxville to Pittsburgh and back everyday, I think you'll be very happy with what you've done
2. Brakes(forgive me if already addressed?)
3. Torque converter
4. Torque converter
5. Torque converter
Engine=
1. Torque converter
2. Truck Norris cam(to best my research it gives most bottom end torque of cam options)
3. Small turbo= 67ish mm pushing about 6psi
4. Stroker
Of all these (brakes for safety-unless addressed) the torque converter and a trans tune to maximize it will be most beneficial



imho, deja-vu is a sign reassuring that you are where you're supposed to be in life at that exact moment. imho, we're shown signs like this on a regular basis.....but and your eyes and your mind must be open to see them. This one really resonated with me yesterday. Went back and listened to it 3 times as day wore on.....but I didn't see what I was supposed to do with it until just now (from 14:05 - 15:30) :

Also, because you wanted/needed to build some trust with and learn some things about your tow rig; learn how to navigate the "aftermarket"; and learn that @swathdiver can find any part anywhere any day of the week! ...and most importantly: you empowered yourself to be less reliant on others! Gained confidence in your ability to overcome adversity and unforeseen issues. And added value to your personal and financial portfolio! [ $7500 truck worth $14k now ]

+ 1 on @donjetman solution. I use a 24" wood clamp with the roll pin removed so can turn clamps around and make a spreader. If you pump then hold pedal down w/foot, then place the spreader on brake pedal and pump the other end far enough into the seat cushion, when you open bleeder screw the cushion rebound will give you just enough of a pump on the pedal to do the job. * * IF you're using the Tech 2(or other bi-directional diag tool) to fluctuate the diaphragms in the ABS box, AS you open the bleeder * *

Pretty sure I'm going to get a lower dash panel w/factory controller on it from salvage, wire it in and make sure it's activate with Tech 2(if it ever get here). That means I have a never used Tekonsha P3 for sale, with GM wiring plug

Click to expand...

Thanks for the kind words and encouragement! I don't think I'll quite get to the level of the guy in the vid with fabbing my own lift kit, but this was a pretty significant job for me. (Not the worst though - it took me two years to get through engine rebuild and complete front end rebuild in my '76 Corvette 13ish years ago.) but it always does feel good to get big projects like this done on my own (albeit lots of help from y'all here!)

As for your list, LOL. Yep, torque converter, I get it. My rig has 202k on it. Not sure if trans is original, carfax doesn't show a replacement, but who knows. It doesn't drive like it has 202k on it, that's for sure. Pretty flawless shifting from what I can tell. Better than my '09 with 6L80, also with a lot of miles. But anyway, I've been told not to do TC with the unknowns on the trans. So I'll probably do them together. Not sure if I'll wait till one of them goes, or do a preemptive rebuild. No turbos or superchargers for me - if I do anything it will be a 6.0 from a same-vintage 3/4T Silvy. I am interested in the Truck Norris cam though. I'd like to keep VVT - is there an option for that?

I had the same idea about adding the OEM trailer braker controller. Looked it up here and found a different thread about someone wanting to do that. But I saw that someone had posted an answer similar to @swathdiver 's (maybe it was Swathdiver) - i.e. that it would be very difficult to do so. Bummer. Love doing things OEM when I can.