Build thread - 3.08 to 3.42 front and rear gear change

[DaveO9]

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.

 

[Geotrash]

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.

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.

 

[mikez71]

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

 

[donjetman]

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.

 

[5StarCustmSolutns]

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.

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?

 

[5StarCustmSolutns]

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

and: AXN

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

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

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

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 ]

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

+ 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 * *

Install a decent quality brake controller

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

 

[swathdiver]

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

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".

 

[DaveO9]

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.

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.

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.

 

[DaveO9]

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?

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

 

[DaveO9]

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

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.

 

[Geotrash]

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?

Yes. Texas Speed makes some good VVT cams for these engines. That said, I deleted VVT when I did my cam upgrade on my 2012 and haven't missed it. I get to drive my stock 2007 with the L92 (has VVT) back-to-back with my cammed 2012 all the time, and the difference is really stark. I'm running the Cam Motion Stage 2 Truck Cam which was ground specifically for the 6.2 (3-bolt, no VVT), and it's so much more satisfying. The power is instant and strong, even at low RPMs.

Best I can tell from hours of reading, is that the VVT system was mainly put in for fuel economy reasons and it's only good for maybe 15 ft lbs down low in stock form. That said, those that have VVT on larger cams (which come with the penalty of needing a phaser limiter to avoid bending valves), seem glad they kept it. All I can say is I don't miss it. The 6.0 and 6.2 have the same 823 rectangular port heads - legendary.

Note that the Truck Norris and Cam Motion cam I mentioned both have very similar specs except for the LSA. The Cam Motion is 117 vs 107 for the Norris. That Norris will have a choppy idle as a result, which I found to be most unpleasant in daily driving. The surging at traffic lights got really annoying with my previous BTR stage 2 truck cam at 111 LSA (generally the lower the LSA, the more idle chop there will be).

 

[5StarCustmSolutns]

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".

Even if mine has the factory wires for it?

The Tekonsha is installed and fully functional, just hasn't been used to tow yet... Wires were factory buttoned up and labeled under steering column... I bought the plug, soldered and sealed it on and P3 worked?

Thanks for the kind words and encouragement!

You're welcome, you earned 'em

it took me two years to get through engine rebuild and complete front end rebuild in my '76 Corvette

I have a 1980 with 53,116. Only thing not original is the radio...and two of them showed up 10mi from me 2weeks ago. Couldn't believe my eyes. Guy wanted $20 a piece lol

I've been told not to do TC with the unknowns on the trans. So I'll probably do them together.

me too and in my case I would say that is a law. Nov will be 3yrs since I first started experiencing TCC lockup, I have a LOT of time in research on the JMBX TC and it's assoc issues.. But if yours is performing that well, and you feel like you need more pull power, I wouldnt hesitate

I am interested in the Truck Norris cam though. I'd like to keep VVT - is there an option for that?

Truck Norris > VVT by wide margin, but needs tuned for optimal performance. Very good friend, Avionics Eng, always says "it takes more than one thing to bring down a plane" ... VVT is one of the culprits responsible for TCC lockup issues. But, yes there are VVT cams available Texas Speed and Mast are two I know, prob several more

Bummer. Love doing things OEM when I can.

OEM is item specific for me. OE brake control is far more aesthetically pleasing than aftermarket.. Tekonsha is better system, but eyesore.. One of top reasons I came over rom CAFCNA(Avalanche) was: unlike most automotive brand specific forums, the braintrusts here understand that auto engineers are kept in a box by the greed of the stakeholders. Which forces them to use inferior ____(options). Unfortunately, those same greedy dudes own a bunch of the aftermarket companies too lol(but not really funny). There's also many aftermarket items that don't perform as claimed, are inferior to OE, or are complete scams! I want to think EVERY part of every automobile is the best it could possibly be (because that's how it should be)....I now know better.. I also used to think wickedness only lived in the darkest corners of a basement somewhere....I now know better

Imho, (much like life) it comes down to ones own ability to discern what is good/beneficial and achieves the desired goal from what is/does not? ...and I agree.....it sure helps to have a resource like this one

 

[swathdiver]

Even if mine has the factory wires for it?

No you don't, not for the factory one. We all have the wires for an aftermarket one. A GMT900 truck originally equipped with the integrated trailer brake controller will have RPO JL1.

 

[5StarCustmSolutns]

No you don't, not for the factory one. We all have the wires for an aftermarket one. A GMT900 truck originally equipped with the integrated trailer brake controller will have RPO JL1.

10-4 that's a copy! ....and thanks for crushing my dream of an ergonomicallly correct aesthetically pleasing cabin


What you do with that gear pattern??

 

[DaveO9]

I have a 1980 with 53,116. Only thing not original is the radio...and two of them showed up 10mi from me 2weeks ago. Couldn't believe my eyes. Guy wanted $20 a piece lol

I've had my '76 for 23 years - July of 2001. Bought it just a few weeks before my (still) wife and I got married. I've done a lot to it over the years, including paint, but I brought it BACK to the original silver, matched to the paint code in the door jam. Block is original, but it's bored, and I have vortec heads on it from a late 90s truck. I still run a q-jet, but not the original one. Still have the original and plan to rebuild it with parts from Cliff's Hi-Perf some day. Great driver car, but not much more. Just there to have fun with. Oh, and my radio IS original. but I have a FM modulator installed inline with the antenna so I can plug my phone in or an MP3 player.

 

[swathdiver]

10-4 that's a copy! ....and thanks for crushing my dream of an ergonomicallly correct aesthetically pleasing cabin


What you do with that gear pattern??

Sorry man, but I would have felt worse if I saw you spending money on something that wouldn't work.

I've decided to send it. Still sitting on the work bench, waiting for the weather to cool off a bit and the rains to stop or slow down to get the axle dressed up with new brackets, brakes, etc.

 

[5StarCustmSolutns]

Sorry man, but I would have felt worse if I saw you spending money on something that wouldn't work.

I've decided to send it. Still sitting on the work bench, waiting for the weather to cool off a bit and the rains to stop or slow down to get the axle dressed up with new brackets, brakes, etc.

Send it! The way I understood it, if you cant hit dead center on drive side, you're better to be a few hundred thou more toe than heel. IF there's wear over time it's more likely to be drive than coast which will, in effect, move the ring away from the pinion a couple 0.00001's(not much), which is what one would do in yours if they had a magic wand...

Sorry I don't have the photos of mine yet to share...

I've spent virtually all my spare time in the last few months:

Prepping for my 6L80 tear down and rebuild. It was pretty rough goin early... Then I finally reached out to the first man I ever saw use HP Tuners to breakdown the way GM has the TCC slip rate %'s setup, and show how he corrects the issue....Mr Hiram Gutierrez. Didn't hear back for a couple months... Then bang....he replied, sent me both GM build and tech manuals, advised about concerns, etc.. We've become modern day penpals since lol

Learning as much as I could get builders to explain to me about torque converters...

Then 62 days ago stumbled onto Backroads of Appalachia and the 24hr Rally events and have been flat buried in off road suspension geometry since... Kingpin angles and scrub radius as pertains to off-road (totally different than on road!) , 3-links, 4-links, triangulated 4-links, SAS, leaf packs, inverted leaf packs, coil/shock, full air, rebuilding high end off-road coilovers and shocks, the pro's and cons of the different styles of lifts, what actually is the most beneficial for clearance/wheel travel/articulation/durability/etc, long travel vs mid travel, wheel size, tire size....you name it!

....and to be honest: This suspension stuff and deciding how I'm going to maximize my GMT900 platform for on /off/tow/performance has been the coolest most intriguing research Ive ever taken on

 

[5StarCustmSolutns]

Best I can tell from hours of reading, is that the VVT system was mainly put in for fuel economy reasons and it's only good for maybe 15 ft lbs down low in stock form. That said, those that have VVT on larger cams (which come with the penalty of needing a phaser limiter to avoid bending valves), seem glad they kept it. All I can say is I don't miss it. The 6.0 and 6.2 have the same 823 rectangular port heads - legendary.

Note that the Truck Norris and Cam Motion cam I mentioned both have very similar specs except for the LSA. The Cam Motion is 117 vs 107 for the Norris. That Norris will have a choppy idle as a result, which I found to be most unpleasant in daily driving. The surging at traffic lights got really annoying with my previous BTR stage 2 truck cam at 111 LSA (generally the lower the LSA, the more idle chop there will be).

These two pararaphs contain the type of info you generally only find behind a paywall!

A+