What did you do to your NNBS GMT900 Tahoe/Yukon Today?

[j91z28d1]

Decisions, decisions!

In our case, we already have the gears for the rear axle and everything to overhaul it, just have to do it and then figure I'd pick up a junkyard front differential with 3.73s and stick it in and overhaul the original at my leisure. PLus, we're taking the truck out west later this year. Do I make the trip with 3.42s or 3.73s? LOL

what brand gears did you go with.. I used to be the gear guy at a shop for a year as a kid. only because I was the only that would do them lol.

I found if you use motive gears in a gm(they supply gm) or Ford Motorsport gears in a Ford. they are 95% a direct swap shim wise. just reuse the stock shims that you took off. slap it together, measure backlash and check wear pattern and it was good to go. pull apart, clean up and final assemble.

any other brand you might as well start from scratch and take it apart 5 times to get it right haha.

 

[swathdiver]

yeah see. mines the 6.0 hybrid with the 2ml70 tranny. it's so different then anything I've have modded before. makes it interesting to me and I only tow maybe twice a year and not a big rv but I would like to upgrade to enclosed car trailer at some point.


these have 3.08 gears in my year but back earlier the caddy had 3.42 gears. but they all switched to the common 3.08 about 2010. no tow rating change, still the small diff size and over all better mileage.

the high gear is 4th and I've have to double check but I believe it's a 0.74 ratio. which if I want the higher rpm of a 3.73 I could just tow in M4. there's no actual overdrive or lock up in a converter. just the veriable ratio of 1.7 or something like that, if I remember right can bring that 0.74 down to a 0.50 to keep rpm down. I've read how this works like 5 times and still can't fully wrap my head around it. it uses planetaries and the speed of one the internal electric motor to change the ratio to almost anything of that planetarie. it's kinda a cvt that doesn't wear out that is constantly changing to bridge gaps between the 4 main gears and produce over drive too.

but when on the interstate it basically trys to keep the rpms the lowest for mileage. on flat ground it would roll along at 0.50 ratio (it shows the ratio in the scanner) but as you go up and down it looked like once it opened the TB to 50% even if you don't move the throttle pedal much, it raises the ratio and the rpms go up. while watching mpg fall. so after a few hours of watching this it got me wondering if i could add hp to the engine at less throttle opening if it would say in (high gear) longer getting better mileage.

so like these are the modes.

View attachment 402231

View attachment 402230

and this is what you get ratio vs speed.
View attachment 402232


as someone that's never liked automatic trannys. this one scares the hell out of me plus is also very interesting.

Cool stuff for sure. Just be careful and take care of that transmission. Nobody wants to work on them and parts are getting hard to come by.

As for the engine, yes, you can make more power with it but you want torque down low and that's a supercharger or displacement increase thing. A mild camshaft, very mild will make a little more power without sacrificing low end torque.

 

[swathdiver]

For what it's worth, we've run into a handful of other campers now who told us they worked their way up to a 5th wheel and then decided it was too much and went back to a smaller bumper pull. They cited costs, maneuverability and overhead clearance in places like gas stations, difficulty finding campsites big enough, and some found that they just didn't need or want the extra space like they thought they would.

We need an office and my wife wants room for 20 guests! LOL I need to bring her to the local RV dealer for a reality check.

A smaller one has to be able to handle my fat behind, those 5/8" floors would be protesting with me walking over them, not to mention pulling the screws out of the floor on the john!

 

[swathdiver]

what brand gears did you go with.. I used to be the gear guy at a shop for a year as a kid. only because I was the only that would do them lol.

I found if you use motive gears in a gm(they supply gm) or Ford Motorsport gears in a Ford. they are 95% a direct swap shim wise. just reuse the stock shims that you took off. slap it together, measure backlash and check wear pattern and it was good to go. pull apart, clean up and final assemble.

any other brand you might as well start from scratch and take it apart 5 times to get it right haha.

Well, since the axle is from AAM, that's what I bought for it, AAM ring and pinion, parts and u-joints. I'm still on the fence on whether to go with 1415 u-joints and a new driveshaft. I want to enter her in a sled pulling contest someday!

 

[Geotrash]

We need an office and my wife wants room for 20 guests! LOL I need to bring her to the local RV dealer for a reality check.

A smaller one has to be able to handle my fat behind, those 5/8" floors would be protesting with me walking over them, not to mention pulling the screws out of the floor on the john!

Yeah, the extra office/bedroom on some of the 5th wheel floorpans is real nice. If my wife and I are still remote workers in 6-8 years, we may want that option too.

 

[j91z28d1]

For what it's worth, we've run into a handful of other campers now who told us they worked their way up to a 5th wheel and then decided it was too much and went back to a smaller bumper pull. They cited costs, maneuverability and overhead clearance in places like gas stations, difficulty finding campsites big enough, and some found that they just didn't need or want the extra space like they thought they would.

I could see that, my coworker upgraded from a 5th wheel to a full class A. he's used it twice in about 4 years. where they used to use it 4 times a year. but they don't really go anywhere, just part of a local rv club and never more than an hour or 2 drive away.

the big one now just sits at a storage lot. he wants to sell it and be done with it, but his wife keeps thinking they are going to use it again.

 

[j91z28d1]

Well, since the axle is from AAM, that's what I bought for it, AAM ring and pinion, parts and u-joints. I'm still on the fence on whether to go with 1415 u-joints and a new driveshaft. I want to enter her in a sled pulling contest someday!

makes sense. my theory was always that whatever company that makes the gears has its own tolerance and hopefully are all pretty close, but change brands totally different. so buying what's in their already makes sense.

lol. normally I'd say the drive shaft is fine but sled pulling everything goes out the window haha.

 

[j91z28d1]

Cool stuff for sure. Just be careful and take care of that transmission. Nobody wants to work on them and parts are getting hard to come by.

As for the engine, yes, you can make more power with it but you want torque down low and that's a supercharger or displacement increase thing. A mild camshaft, very mild will make a little more power without sacrificing low end torque.

yes.. I've changed the fluid as soon as I got it. and sent off a sample when I got back.. I am leaning towards dumpping it one more time and switching to amsoil before this next trip. after that, eh keep in cool and change every few years.

I half wanna pick up a spare when I see one for cheap just incase. I usually keep vehicles way way to long haha.

cam is funny, it's got its only special cam too, because of course it does haha. hp tuners doesn't have much definited, so I'm not sure I could tune for a cam anyways.

boost would be the way, as I can tune the open loop PE fueling, just not tweak the closed loop stuff a cam would need.

 

[iamdub]

Good process of narrowing down any parasitic drains from the stuff you've added.

I've had some mixed results with AGM batteries behaving in exactly the same way in older vehicles. Most recently in our '05 Infiniti G35X. It acted EXACTLY like there was a parasitic drain, and the AGM battery was maybe 18 months old, IIRC. It would go dead within 48 hours and I spent a ton of time trying to find parasitic drains. Swapped it with the cheapest Autozone conventional battery I could find, and now it often sits for 2-3 weeks without being driven, no problem at all.

One theory I have is that the factory alternators on our trucks (and most pre-2015 cars) don't charge AGM batteries in the way that they need to be charged for longevity. It's purely a theory, but when I replaced the alternators in both of mine with new Chinese units and new AGM batteries, I haven't had a problem since and it's been 4 years on one of them now. Prior to that they both ate new, expensive, German AGM batteries within a year.

Well, this is a bit concerning. I installed a new German-made AGM EverStart about 6 weeks ago. But I also installed a 220A alternator from a much newer (2019, I think) truck.

 

[j91z28d1]

Well, this is a bit concerning. I installed a new German-made AGM EverStart about 6 weeks ago. But I also installed a 220A alternator from a much newer (2019, I think) truck.

do you have hp? it sounds like you can go in and change the settings on the battery voltage so that it runs what agm likes all the time?