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GTMOTORSPORTS

New member
Need some advice on a project. Im workingon a 6.0 swap into my 97 Olds Bravada. I am in the planning stages right now. I do know the transfer case makes a clunking sound with the front shaft in it. I was told by a GM tech that the viscous coupler was bad. I had the same guy remove the case and he said he could weld the coupler together. It didnt help. So can I get a new viscous coupler from GM or is there some place you recomend that sales them. Or is there a different transfer case that is better suited.

I saw Justdreamn did a swap in his Bravada to remove low gear? How hard id that to do and what did the transfer case come out of and will it bolt to the 4l60 transmisson?

I have the headers,engine mounts,and wiring harness mostly figured out but im up in the air on the transfer case deal. Any help you guys could give me would be appreciated. This site seems to know the most about GM drivelines than any other site Ive been on.
 
J

'JustDreamin'

Dream: 6LV8 Turbo Bravada
Re: Options

Here's what I know....

The Bravadas changed transfer cases between the '97 and '98 model years (I'm pretty sure).

Your '97 and all older Bravadas (and all Sy's and Ty's) use the BW 4472, which is a full mechanical tcase with a viscous coupling.

'98 and newer use the NV136 tcase which is an electronically controlled "on demand" tcase. My truck is a '99, so it originally had a NV136, which I changed out to a NV246 with low gear removed, so that is mated up with the 4L80E that I installed.


So, for your application, you really only have one practical solution, repair the existing transfer case by replacing the viscous coupling (Parts are available, they're not cheap) or replace it with an identical (but fully functional unit) either from a salvage yard or rebuilder. The viscous coupling cannot be repaired, welding it up is not a solution, and anybody who tells you it is should never touch your truck again.

There are obviously a bunch of other tcases available.
1.) The NV136 (or 146 / 246 like my truck has) will require a bunch of electronic controls, which is possible but probably not a practical solution.
2.) Silverado SS tcase, which is the NV149 is also a VC type tcase, has a reputation for going bang, so it probably isn't a good choice.
3.) Trailblazer SS tcase is a good choice, I believe its fully mechanical (supposed to have a Torsen diff in it), however it isn't the most available piece of hardware (so cost may be an issue).

There aren't that many AWD type tcases available (list above is about it, probably a few Jeep boxes but those probably don't mate up with a GM trans). Any tcase that does not include some kind of device to allow different speeds front to rear (differential, viscous coupling, etc) wont work on pavement for long. This is pretty much any part time tcase.


The 4L60E trans is your weakest link. Depending upon the amount of power you're going to be making, it may or may not survive long term. If you've got the funds, you might think seriously about picking up the 32 spline input shaft for the tcase (there's a group buy going on, look for it). That will allow you to run the 4L80E, which is a MUCH stronger trans. But then you've got to change the whole trans and controls (electronics for the trans). Good news is that the PCM for the 6.0 can control the 80E, so that you don't have to have 2 pieces of hardware.


So, how are you handling headers, engine mounts, and oilpan?

'JustDreamin'
 
G

GTMOTORSPORTS

New member
Re: Options

Just,

Thanks for the info. I have been building rides for several years now.So Im not completely lost.Just couldnt find any info on these drivlines.

I do know there are a few places like advanced adaptors that make adaptors for the jeep cases to chevy trans. There are a few others also. I have a 2wd 4l80e out of my 97' dually that needs rebuilt. Could I swap the 32 spline input shaft in to the 2wd case and run the NV136/NV146/246?

I only plan on around 380-400 H.P. As far as the Headers go Im looking at the mid length 2wd ls1 swap headers,on performance trucks.net I have a guy who used a set there.If not Ill mod a set. I do exhaust work frequently. im also going to build my own Y pipe and exhaust. and Im going with the 2.8 mounts,Ive been told they work great..If that doesnt work Im going to try the welderseries bolt on mounts . The oil pan is another triued and true swap using the H3 hummer V-8 pan.

As far as the welding the coupler..im not sure what he was trying to do but usaully he is a good tech guy. Yeah the coupler is like $800 from GM.Thats the only place I have found it.
Again I really appreciate the info. Ill start posting pics when I get most of the pieces together.

Im also going to four link the rear with coilovers. Im also going to fab my own upper and lower control arms for the front to run coilovers.
 
J

'JustDreamin'

Dream: 6LV8 Turbo Bravada
Re: Options

GTMOTORSPORTS said:
Just,
I do know there are a few places like advanced adaptors that make adaptors for the jeep cases to chevy trans. There are a few others also. I have a 2wd 4l80e out of my 97' dually that needs rebuilt. Could I swap the 32 spline input shaft in to the 2wd case and run the NV136/NV146/246?
Click to expand...

You can convert a 2wd 80E into a 4wd 80E. The output shaft of the trans has to be changed, which requires taking the entire trans apart (it's the first thing in and the last out).

The problem with the NV136 / NV246 (NV didn't actually build a 146, mine is just a 246 with the low range left out) is that it requires the controls to make it work. Those controls are in the BCM, not the PCM, and your '97 truck won't have the right bits. Obviously, you can swap them, but that ramps up the degree of difficulty. Or you could design your own controls, I'm sure that it can be done, but I'm not sure if the motor that runs the clutch is looking for PWM or some other operations scheme.

Difficulty wise, it'd be alot easier to pick up the 32 spline input shaft for the BW4472 tcase (see the group buy) and retain the 4472. Even knowing that you've got to fix yours with a fresh VC.

GTMOTORSPORTS said:
I only plan on around 380-400 H.P. As far as the Headers go Im looking at the mid length 2wd ls1 swap headers,on performance trucks.net I have a guy who used a set there.If not Ill mod a set. I do exhaust work frequently. im also going to build my own Y pipe and exhaust. and Im going with the 2.8 mounts,Ive been told they work great..If that doesnt work Im going to try the welderseries bolt on mounts . The oil pan is another triued and true swap using the H3 hummer V-8 pan.
?
Click to expand...
Good luck with the headers, no idea if they're even close. I know its pretty tite under there, what with the front diff, front propshaft, steering shaft, and front frame rails all basically in the way on the drivers side. Pass side is a bunch easier but still not a cakewalk. You'll definitely be on your own for a Y pipe (I used a 2.5" to 3" Y and a 3" high flow cat and a bunch of mandrel bends to fabricate mine). There are a couple Cat back systems available, that you could make work. I used a 3" catback system on my truck, just had to fabricate everything ahead of the stock cat flange (and open up the stock flange to 3").

I wish you luck with the H3 pan. I haven't held it in my hands, but from the pics I've seen, I don't see how it could fit. However, if you make it work, I'd be happy to be proven wrong. I just know that the space that the front diff and oilpan occupy is pretty snug.

GTMOTORSPORTS said:
As far as the welding the coupler..im not sure what he was trying to do but usaully he is a good tech guy. Yeah the coupler is like $800 from GM.Thats the only place I have found it.
Again I really appreciate the info. Ill start posting pics when I get most of the pieces together.

Im also going to four link the rear with coilovers. Im also going to fab my own upper and lower control arms for the front to run coilovers.
Click to expand...
I'm pretty sure some folks on here had located a lower cost source (in the ~$400 range) but not sure who that was. Might have been a supplier who no longer is on the board. Do a little digging (searching), and maybe post on that specific topic if you can't find any help.

'JustDreamin'
 
G

GTMOTORSPORTS

New member
Re: Options

JustDreamn,
Ill follow your advice on the Transfer case. Thanks.

As far as the headers,I guess all I can do is buy a set and try them.Jegs is only 1 hour form the shop. If they dont fit then I will have to Fabricate my own. I heard stock manifold from any ls/lq engine will not work either. As far as the Y-pipe. I figured Id be on my own there also.I have a place to get wholesale mandrel bent tubing an all sizes. I know Flow master sales a Y merge with 2 1/2" in and 3" out,I have had pretty good luck with those.In Ohio we have no E-check so Im not sure if Ill run a cat or not. If I do it will probably be a Dyna tech. I have installed a 3" cat back on a friends blazer several years ago.It was from hooker and used an Areo chamber mufler. Im sure there is probably more available now. If not I will buy some 3" tubing and fab my own.

The H3 pan was just something I was told may work. Just like this whole planning stage Im up in the air. thats why Im trying to get info on these parts. No one likes to buy 2-3 times to get it right,if they don thave too. If not Ill will try to mod a stock pan. I think some guys are modding F-body pans,Is that correct? This isnt my first build on a custom vechile. Just never attempted this swap before.

Ill search and see what I find.Thanks again.
 
J

'JustDreamin'

Dream: 6LV8 Turbo Bravada
Re: Options

The fun with modifying the stock pans is that they're aluminum. Many folks (myself included) don't have the equipment & talent to modify the stock pan. And given that they're castings (with the resultant porosity) that contain oil, it can be a challenge to get them clean enough to get good welds. And the amount of heat required can warp the pan. So, if you're going to modify, make sure you bolt it down to something (like a junk block or a big chunk of steel plate or something) to keep it flat. And get it as clean as you can (degrease, degrease, maybe bake in the oven, run through the dishwasher, etc).

Because of those limitations, I ended up building my own pan out of (steel) sheetmetal & barstock. Gave me the flexibility to do what I wanted. I relocated the oil filter out of harms way with -8 or -10 AN line (can't remember what size off hand). But I also have access to a pretty full machine shop, so making the flange and making sure it was flat after welding (ended up flycutting it) wasn't a big deal.

TurboTime was offering a set of engine mounts and a custom alum pan at one time. Not sure if they're still available.


I think the 2.5 to 3" Y I used was Flowmaster. I also used a couple of band & flange type couplings (like turbo parts) to put the exhaust together. They don't leak and they take less space than 3 bolt flanges.


I used a set of f-body manifolds for the exhaust, but I had to modify them significantly. I don't know that its an ideal solution, but it's worked for 25k miles. Welding on cast iron is supposed to be a no-no, but it seems to be holding ok. Basically, I ended up hacking off the f-body flanges and welding 2.5" tube extensions to them to get the exhaust where I needed it to go. Oh, and I ended up removing the EGR bump on the pass side manifold (hit the shock tower) and filling it with a section of 2" black steel pipe. Again, I wouldn't say an ideal solution, but custom headers were not in the budget or the timeframe.

Good luck!

'JustDreamin'
 
G

GTMOTORSPORTS

New member
Re: Options

Yeah i know all about the porsity of the aluminum. I am a welder/fabricator by trade and build cars/trucks on the side. So yeah its a pain. I weled a case on a muncie 4 spd for a guy..even tig welding it it was a nightmare.

I have thought about fabbing my own pan. I have alot of suspension brackets laser cut and I thought if I made a CAD file on the out line of the pan I could have them laser cut it for me. theni could build the pan from there. Just an option I was exploring.

I thought of using the same style clamps. Alot easier to work with. I used to be a diesel mechanic and they were nice to work with on big trucks.

I kno wthey say not to weld cast. But if you pre heat it and use the right rods its no problem. I have welded on cast housing for off road jeeps and on 3 links for trucks and cars. Never had an issue yet. I will try to make something happen. I was at Jegs yesterday and saw there laser cut flanges. They were 3/8" thick and very nice piece.so if nothing else I will start from scratch.

Ur50slo,Thanks for the link.Im a member there also..95/02ss..thats a good write up.
 
J

'JustDreamin'

Dream: 6LV8 Turbo Bravada
Re: Options

GTMOTORSPORTS said:
Yeah i know all about the porsity of the aluminum. I am a welder/fabricator by trade and build cars/trucks on the side. So yeah its a pain. I weled a case on a muncie 4 spd for a guy..even tig welding it it was a nightmare.

I have thought about fabbing my own pan. I have alot of suspension brackets laser cut and I thought if I made a CAD file on the out line of the pan I could have them laser cut it for me. theni could build the pan from there. Just an option I was exploring.

I thought of using the same style clamps. Alot easier to work with. I used to be a diesel mechanic and they were nice to work with on big trucks.

I kno wthey say not to weld cast. But if you pre heat it and use the right rods its no problem. I have welded on cast housing for off road jeeps and on 3 links for trucks and cars. Never had an issue yet. I will try to make something happen. I was at Jegs yesterday and saw there laser cut flanges. They were 3/8" thick and very nice piece.so if nothing else I will start from scratch.

Ur50slo,Thanks for the link.Im a member there also..95/02ss..thats a good write up.
Click to expand...

If you're looking at having anything laser cut, I'd say the oilpan flange would be a reasonable choice. I made mine out of 4 pieces of 3/8" flatbar. Welded it into a rectangle, spotted and drilled all the holes, then cut the outline with a bandsaw to match the pan. Making it 1 piece would make it a bit easier, but the cost would go up. The rest of my pan was 18 ga sheet. If I had a bit more patience while welding it up, I probably wouldn't have had to straighten it / flycut it.

I ended up MIG welding the manifolds. I thought they turned out pretty decent. No preheat or special rods, just normal 70 series wire and 75/25 mix. And so far they've held up, although I can't say that I've inspected them all that closely visually, they don't sound like they're leaking (usually that's pretty obvious).

Like I said earlier, good luck with your project. The swap certainly isn't cheap, but it's alot more fun to drive than the V6 ever was.

'JustDreamin'
 
G

GTMOTORSPORTS

New member
Re: Options

Cloneman315,
What do you want for it? How many miles are on it?


JustDreamn,
I will make a jig to hold the pan rails flat and keep my patience about me. I know what its like to want to rush. I too have migged cast iron with good results.Thanks for all the advice. I bet your 99 Bravada is a blast.

Im hoping to get started as soon as I get a few other projects finished for customers. Then its game on. i think so far I have enough info to get my self into troubel..hahahha.
 
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