Trying to get my info straight... (axle/driveline specs) ...potential project

layinbody31

Original poster
Member
Apr 2, 2012
4
Ok, so what I've gathered from reading on here and other sites is that there are 3 different rear ends that were put into the TV trucks.

The major breakdown between them all comes by model year due to differences in the ABS. The 2002-05s do not have any ABS sensors on the axle, but the 2006-09s do (02-05 uses the speed sensor in the trans/transfer case to control the ABS for a 3 channel setup, whereas the 06-09 has a 4 channel setup).

The standard 113" wheelbase trucks have an 8.0" 10-bolt rear end in them with 3.42 (GU6), 3.73 (GT4), and 4.10 (GT5) ratio's available. Was this rear end still used even if the truck got the 5.3 V8?

The EXT (129" wheelbase) trucks have an 8.6" 10-bolt rear end in them with the same ratios available. (I'm thinking these were also put in the 5.3 V8 standard wheelbase trucks, but not sure). This rear end shares many internal components with other GM 8.5" 10-bolt rears but the outer housing is different

The SS trucks have a semi floater 9.5" 14 bolt rear that is the same as found in 2500/HD fullsize trucks as well as other GM vehicles (granted the suspension mounting points, width, bolt pattern, and brakes are all specific to the TB and also the SSR's that got the 6.0). They were only made available in the TBSS's with the 4.10 ratio (GT5)


As far as transfer cases go, the SS's got the AWD NR9 transfer case. Were there any other models besides the SS that this tcase got put in? The non-SS trucks then either got the NP4 or NP8 tcase. Can anybody tell me what the difference is between the two?


Lastly, when it comes to the front differentials, is there any difference in size of those between standard wheelbase/EXT/5.3/SS? Or did every TV get the same size one, just the ratios are different to match the rears?




What I'm wanting to make sure is if my '05 TB LS 4.2 4x4 standard wheelbase has the 8.0" rear. By everything I've read it should, but I'm hoping there's some chance I'm wrong and it has the 8.6". I come from the S10 world where the 8.5" rear is the holy grail of stock S10 rear ends, and if my TB has the 8.6" (which is essentially the same as an 8.5") it would work out well for me.

What I am wanting to do is upgrade my rear in my TB to a 9.5" like the SS's have. Instead of buying an expensive SS rear (which is '06up and would mean I'd have ABS sensors built in that would be useless to me), I was thinking of trying to just find a rear out of a 2500 pickup. They can be had for much cheaper and then I could actually find a rear that has either a 3.42 or 3.73 ratio (to match what my TB already has, because I'm pretty positive it's on of those and not 4.10s). Then I'd also not have to purchase gears to change a TBSS rear to match my front gears (or regear the front diff to 4.10... I'd rather stick with one of the lower ratios anyway). If I swap rears in the truck I plan to narrow the new rear 1" per side from stock, since I'll be bagging eventually and that will be necessary to tuck, so having a fullsize pickup rear that's wider than a TV rear won't be an issue since either rear will get narrowed anyway. Narrowing means I'd need new axle shafts too, so redrilling from fullsize pickup bolt pattern to TV bolt pattern would be a non-issue, as I'll just have the new shafts made up with a TV bolt pattern. I would just need to verify that the brake mounting flange/pattern is the same so that my TV brakes would mount up, and also that the Ujoint size is the same so that will fit as well. I realize I'll probably need to either have my driveshaft shortened or get a driveshaft out of a TBSS when I do the swap. Then I'd simply cut the 4link/panhard/shock/spring mounts and bumpstop pads off my current rear and re-install them on the new rear and be good to go.

Now, that brings my to why I'm hoping my rear is an 8.6". I have a project S10 that I need a new rear for, and have always just planned to find an 8.5" S10 rear (plenty strong to handle the power I want to put through it). Well I also plan to narrow that rear, so that opened up more possibilities of rears I could use (I could branch out into 4x4 S10 rears and especially ZR2s). It also led me to think that if I have my current rear out of my TB sitting around, and it's essentially the same as an S10 8.5" (if it's the 8.6"), that I would just narrow that and use that in the project S10. Of course narrowing would mean an easy change on the bolt pattern, just like putting the 9.5" into the TB. Secondly, my daily driver S10 has an 8.5" that I swapped into it, but it is a 3.42 ratio and I'd like to switch it to 3.73, and it's also an open rear end and I'd like to add a locker/limited slip to it since it's 2wd and isn't good in winter with an open rear. Since all the internals in the 8.6" are the same as the 8.5" it would allow me swap the carriers and gearsets from my 'old' TB axle into my 8.5" rear that's in my S10 and gain my ratio change and locker/limited slip all in one. And then the 3.42 open rear would be in the project truck which won't be getting a motor for a while so it really wouldn't matter that it's that ratio or an open rear.


I guess if my TB really is an 8.0" rear it's not that big of a deal, as I could get an 8.6" 3.73 G80 rear from an EXT in the junkyard, swap the carriers/gearsets with my S10 8.5", and then put it in place of the 8.0" that's in the TB until I get around to doing the 9.5" swap (Provided my TB is a 3.42 ratio so it matches the front diff. I'd then sell the 8.0" rear). Although that would mean that the TB would have an open rear for that duration of time. But with it being 4wd and having much more weight on the rear tires than my S10 has I'm not sure an open rear would be a problem. I think I did read something about needing conversion bearings or something when putting the 8.5" rear internals into the 8.6" rear housing, so that may be an issue that would prevent the whole thing. And I guess I could also just get an S10 8.5" rear that's 3.73 with a limited slip to swap those internals into my daily and use the housing with the 3.42 open rear for my project truck and then not even have to mess with the TB, although going that route would leave me no rear end to sell at this point to make back some of the cost involved


Then as far as the transfer cases go, if I wanted to switch to the NR9 AWD case and make my TB AWD would there be anything involved in that swap other than switching the tcases?


Sorry for the novel, just trying to wrap my head around some things here. Thanks for any and all help

-Brent
 

The_Roadie

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Nov 19, 2011
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layinbody31 said:
Ok, so what I've gathered from reading on here and other sites is that there are 3 different rear ends that were put into the TV trucks.
My goodness you've done a BUNCH of research. I'm impressed. :thumbsup:
Was this rear end still used even if the truck got the 5.3 V8?
Nope. V8 SWB got the larger diff. There is also an axle spline count increase for the larger one.
..I'm thinking these were also put in the 5.3 V8 standard wheelbase trucks, but not sure
You're right.
As far as transfer cases go, the SS's got the AWD NR9 transfer case. Were there any other models besides the SS that this tcase got put in?
Nope. It's a very special Torsen design with no electronic control. It's more like an automatic limited slip transfer case where the non-SS units use internal clutch packs that can lock up.
The non-SS trucks then either got the NP4 or NP8 tcase. Can anybody tell me what the difference is between the two?
The NP4 RPO code (also called the NVG (New Venture Gear) 126 transfer case was only used in the Bravada and platforms that were full-time AWD. The TCCM fiddled with the clutch packs to transfer torque forward when needed, but their splined disconnect on the passenger side of the oil pan was permanently collared together with no shift fork to disengage it for 2WD mode. There was no 4WD mode selection switch on these AWD platforms. The NP8 (NVG 226) transfer case used different TCCM algorithms, a mode selection switch, and also had a 2.7-to-1 LOW range in the transfer case. For more reading on the theory of operation of the splined disconnect and the NVG226: Offroadtb.com Front Axle 4WD Disconnect and Offroadtb.com Transfer Case Operation: NVG 226 (NP8)

I'm sure there are theory of operation documents out there for the SS Torsen, but I didn't bookmark those.
Lastly, when it comes to the front differentials, is there any difference in size of those between standard wheelbase/EXT/5.3/SS? Or did every TV get the same size one, just the ratios are different to match the rears?
All fronts are the same other than gear ratios. The splined disconnect for AWD is different.
Then as far as the transfer cases go, if I wanted to switch to the NR9 AWD case and make my TB AWD would there be anything involved in that swap other than switching the tcases?
Nobody's ever done it, but as I understand the Torsen is passive and needs no TCCM or electrical involvement. You'd be the pathfinder.
 

layinbody31

Original poster
Member
Apr 2, 2012
4
Wow... thanks for the reply with all the great info! :thumbsup:

It's nice to have the knowledge about the transfer cases now. I found a TBSS AWD NR9 case on craigslist that has less than 500 miles on it and the guy wants $250 for. I'd love to swap it into my TB, but the fact that mine is used to having to control the Tcase via the TCCM and knowing that the TBSS case needs no input for control leaves me wondering if it would cause issues to install it. Would I be able to put it in 2wd via the selector switch in the dash (so no control is being input out of the TCCM) and then just unplug the switch? I'd assume I'd need to leave the TCCM plugged in or I'd have dash lights coming on, but I can't imagine that unplugging the switch would have any such ill effects.

Secondly, I know that the front disconnect is not the strongest, but what if you were to install one on an SS (or if I left mine in place after converting to the NR9)? Would it be able to handle the power/torque of the 6.0L in the SS or would it grenade sooner than later? The reason I ask this is because I love the idea of a true torsen style limited slip AWD system like the SS has, but I also like the ability to function in 2wd. I have a different project S10 than the one I mentioned before and that one is AWD and will be using a Bravada/Syclone/Typhoon AWD Tcase (which operates very similar to the TBSS Tcase, although it's a clutch/governor type setup vs. a torsen design) and I plan to leave a standard 4wd disconnecting front axle in it, so that when engaged gives me true AWD but when disengaged gives me 2wd (although with the front driveshaft and center section spinning). I know it's physically possible to put together a system like this on the TB (by replacing my Tcase with an NR9 or installing the disconnect on an SS) but I just don't know if it can handle the power. I know that on the S10 disconnecting front axle I can simply use a locking cable to control if it's engaged or disengaged, and I'd assume I could set up something similar to work on the TV if I chose to go that route. What leads me to wonder about the strength of the disconnect is because my brother who has an '03 TB LT 4x4 had all the bearings go out on his disconnect in his truck. When rebuilding he chose to go with bravada parts to eliminate the disconnect and leave the Tcase as the only method of selecting 2wd vs 4wd. Yes, this means in 2wd his full front axle and front driveshaft spins, but he felt that the design of the disconnect left parts of the axle shafts unsupported when disconnected and that that was what lead to the failure of his. I read through the article you posted and didn't see mention of an obvious lack of bearing support when disconnected, so I'm not sure that he really needed to go that route or not, but needless to say he did, and he's happy with the result.

The only other question/issue that relates to this whole driveline topic is if anybody makes a limited slip or locker for the front diffs on the TV trucks. If I go the route of an NR9 and leaving the splined disconnect it will do me no good, because if the rear tires ever spin when the truck is in 2wd mode the front locker would attempt to lock the stationary left front wheel to the rapidly reverse-spinning right front axle stub, leaving me with an awkward 3 wheel drive setup, but if I choose to convert to both the NR9 and the Bravada disconnect parts it would be nice to have a locker up front.

Lastly, with the rear axle, do you know of any issues or special bearings/requirements/etc that go along with installing 8.5" internals in the 8.6" rear and vice versa? If it's too much of a hassle I'll just get a ZR2 rear for my project S10 that comes factory with 3.73 gears and a G80 gov-lok so that I can swap it all into the 8.5" 3.42 open rear that's in my daily driver vs buying an 8.6" TV rear to swap internals into and then swap into my TB. Although I did look at my RPO codes and my TB is a GU6 non-G80 rear so it has the exact same setup as the 8.5" in my daily driver S10, so swapping those internals into an 8.6" rear and installing it into the TB would essentially be no change, other than being stronger. But with wanting to go for a 9.5" semi-floater in the end I'd probably be better off not wasting my time with the 8.6" and just going straight for the 9.5", while doing a ZR2 rear for the S10


Again, thanks for all the help and great info! :thumbsup:
 

layinbody31

Original poster
Member
Apr 2, 2012
4
Oh, and do you know what the spline count of the 8.6" is? My S10 8.5" is 30 spline, so if they're different it would mean it wouldn't even work anyway
 

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