Bravada

[ZR2Owner?]

So I did a quick search and I couldn't find anything. My mothers Bravada (99) cannot do turns at slow speeds without feeling like the drive train is totally binding up. For instance, reversing out of a parking spot is almost impossible without having to give it quite a bit of throttle, it feels like its a 4x4. It turns worst then a Canyon, Yukon, S10, and a Blazer. No service lights are on, however about a week ago it was throwing P0420 and P0870. I gave it some oil (previous thread) and I drove it today and it is no longer throwing codes. Another problem I noticed is after some driving (like the transmission warms up) the transmission will slam into gear the 1-2 shift seams the hardest with the 2-3 shift less and the 3-4 not noticeable, Mechanic said it needed to be rebuilt, can you guys provide any figures or is it cheaper to swap out the tranny? However the Mechanic claims nothing is wrong with the AWD, He seems to come across as implying that all Bravadas drive the same disgusting manor. I just have a very hard time believing this part time AWD vehicle which is not much different then a 4x4 blazer could come from the factory like this, nor do I remember it riding this bad when it was new. Any ideas?

[NTL1991]

I'm not positive if the transfer cases are different, but my 97 Bravada turns as well as a regular car. Now, my S-10 would bind while making corners... Going through a drive that wraps around a building was terrible.

I just checked AllData, and there is a TSB for that vehicle entitled "Transfer Case Shudder" which is in response to people complaining about a vibration (shudder) during tight, low-speed (under 5 mph) maneuvers on dry pavement.

Correction involves flushng the fluid with new, fresh AUTO-TRAK II fluid. I'm assuming that it's imperative that you use this specific fluid, as special friction modifiers are key to the proper operation of this transfer case.

Attached is the TSB.

Hope this helps,
Nick

[NTL1991]

Also, was the second code P1870, not P0870? Because there's also a TSB for the transmission regarding a hard 1-2 upshift and P1870 in the computer's history...

If so, the reason why the harsh upshifts occur is because when the computer detects the conditions that set off the P1870 code, the transmission uses maximum line pressure, causing the harsh upshift.

The problem, apparently is in the Control Valve Body in the transmission, but the TSB states that a Rebuild is NOT necessary if all of the following are true:

-Transmission operation is normal before it gets to operation temperature.
-Torque converter is not blue or overheated.
-The transmission fluid is not brown and doesn't have a burnt smell.
-The transmission pan contains no abnormal debris.

This is the link to the TSB for the transmission. You might want to print it out and have your mechanic take a look at it (or if he insists that the tranny needs to be rebuilt, go to another.)

The problem is probably just in the valve body. GM Parts Direct is the cheapest I can find at $290 plus a $50 core charge. GM Part # is: 24221154, as stated in the TSB.

[orangesonoma]

pretty sure since there is no selector for the front axle so that the binding is normal...and as far as the trans...try lucas trans slip fluid....my 98 blazer would throw you in the seat when the trans would shift..i added a bottle of lucas and all my problems went away...

[ZR2Owner?]

Hey, Thanks guys. Printed all this information out and gave it too her then called a GM Goodwrench dealer, they will hook it up to the diagnostic machines for a small fee. She got a quote from the mechanic, the guy must be on crack $4580, Wanting $1800 alone for a rebuilt 4l60e and another $1100 for a transfer case.

[orangesonoma]

it would be way easier and cheaper to throw in a bottle of lucas...it has fixed problems on plenty of trucks

[skatingzooyork]

My 00 bravda doesn't bind at all like that. Once in a while I will feel it a little but nothing to ever even worry about.

I've also driven an awd Chevy Astrovan and that thing binded up a lot at low speed turning; the bravada feels nothing like it!

[NTL1991]

Yeah, binding shouldn't be happening on a Bravada or any AWD car that uses the same type of system. There's a viscous coupling in the transfer case on these trucks that compensates for the different speeds that the front and rear axle move at... On regular 4x4 trucks, there is no "cushion" between the 2 axles when 4WD is engaged which is why binding occurs and also why you shouldn't drive a Part-Time 4WD vehicle in 4WD mode on dry pavement. Dry pavement doesn't allow the tires to slip like they should. Snow, ice, mud, etc. does...

Before I would do any major service on a transmission, I would flush the fluid and change the filter... The cost isn't that much, and you might as well try it as it might just be the problem... BUT, when there's a TSB that references the same exact symptoms and even DTC's, then chances are that the problem is exactly what the TSB is issued for...

As for the price, many, many, repair shops outsource their transmission work to transmission shops. By going to a transmission shop directly, you can cut out the middle man and any excess cost. I don't think that rebuilding the transmission is necessary, especially if the requirements above are all met. If that is the case, then they should be able to keep you transmission (assuming it's in good working order) and just replace the faulty valve body in it.

My .02

Nick

['JustDreamin']

The 97 and later trucks don't run a viscous coupling in the tcase (those marked SmarTrak).

Those trucks (mine included) use an "Active On Demand" transfer case. Basically its a normal 4x4 tcase with a big electrically actuated (by way of a motor) clutch that connects the front propshaft (which is being spun by the wheels full time) to the transfer case front output. Its all in the tcase, btw.

Sounds to me like the transfer case actuator motor is either faulty or it is being told to be on all the time (which it shouldn't be).


You NEED to fix the hard shifting ASAP. Full line pressure shifts with AWD in a 700R4 will break something (in my case it was a planetary set in the trans).


Find yourself a mechanic, not a parts changer (which is what the guy who quoted $4k was). You need someone who can diagnose the problem and fix just the problem and not fix things that aren't broken. Probably easier said than done.

'JustDreamin'

[NTL1991]

Sorry for my misinformation.

But, I'm pretty sure the computer controlled NP-136 transfer case (which uses two speed sensors to sense the difference in speed between the front output shaft and the rear output shaft, and engages the front axle accordingly) was installed in 1998 and later models. 1997 and earlier use the Borg-Warner 4472, which is always engaged with the use of the viscous coupling. Both were marketed as "SmartTrak" though...

As JD said, the transmission would also be at the top of my list...

Nick

[ZR2Owner?]

Well It was brought to a different mechanic, one who had the machines to hook up to it. He said the encoder motor was seized into AWD mode, and the transmission needs a new valve body as previous stated it might. Thing is he quoted $750 for a valve body from GM. I checked GM Parts Direct and couldn't find the valve body or encoder motors, Couldn't find much actually as far as transmission and transfer case goes. Any other sources you guys recommend?

['JustDreamin']

I wouldn't think that the valve body would be all that unique. But I wouldn't put it past GM to make them unique. It's just another reason they're headed to Ch 11.

Nick, you're right, the start for the NV136 is '98, not '97 as I posted earlier. And the Astros started using the NV136 a year later. Sorry for getting my model years mixed up.

'JustDreamin'