2000 Bravada reverse question

We bought this car with 90000 miles on it about a year ago. From the
very beginning we started to notice a slight shudder when backing up.
We took the car in to a friends place and he changed the blue fluid in
the transfer case. He said that there was a problem with the All Wheel
Drive function which affects the transfer cases on these and said "lets
try the fluid change first and see if it helps". After doing the change
there seemed to be little difference but eventually the problem seemed
to all but dissappear. We were very encouraged. The car had been fine
until recently when this transmission had lost reverse, which I am told
is apparently a typical and unrelated problem with these. We had the
trans rebuilt and it seems to be OK except for the fact that the slight
shuddering problem in the drive train is now occurring again
sporadically only in reverse, but not all the time when backing up.
When it happens it seems to be worse if the wheels are turned but it it
so intermittent that it is hard to say if the problem only occurrs when
turning or it may occur when backing up in general. Like I said
sometimes it doesn't happen at all. So far I have just never noticed it
when straight backing up.
So my questions a
1. What is happening here?
2. Did the original problem ruin reverse on the transmission and could
this occurr again?
3. We don't really use 4WD. Can it be disabled thereby saving us a
possible costly future repair again?
4. Might changing the blue fluid help again?
5. Is there a solution that will really "fix" this problem or is this
just a poor design.
Please don't worry about providing as much technical information as
possible. I really want to understand this problem and will sincerely
appreciate it all. Thanks, Lenny Stein.

Thewre were issues with the awd transfer case, there are tsb's relating to
this condition that can require replacing the encoder and/or reprogramming
the pcm. The truck is in awd all the time remember. It is also possible the
locking diff is is binding , an experienced GM tech needs to feel this
happening for an accurate diagnosis.
> wrote in message
oups.com...
> We bought this car with 90000 miles on it about a year ago. From the
> very beginning we started to notice a slight shudder when backing up.
> We took the car in to a friends place and he changed the blue fluid in
> the transfer case. He said that there was a problem with the All Wheel
> Drive function which affects the transfer cases on these and said "lets
> try the fluid change first and see if it helps". After doing the change
> there seemed to be little difference but eventually the problem seemed
> to all but dissappear. We were very encouraged. The car had been fine
> until recently when this transmission had lost reverse, which I am told
> is apparently a typical and unrelated problem with these. We had the
> trans rebuilt and it seems to be OK except for the fact that the slight
> shuddering problem in the drive train is now occurring again
> sporadically only in reverse, but not all the time when backing up.
> When it happens it seems to be worse if the wheels are turned but it it
> so intermittent that it is hard to say if the problem only occurrs when
> turning or it may occur when backing up in general. Like I said
> sometimes it doesn't happen at all. So far I have just never noticed it
> when straight backing up.
> So my questions a
> 1. What is happening here?
> 2. Did the original problem ruin reverse on the transmission and could
> this occurr again?
> 3. We don't really use 4WD. Can it be disabled thereby saving us a
> possible costly future repair again?
> 4. Might changing the blue fluid help again?
> 5. Is there a solution that will really "fix" this problem or is this
> just a poor design.
> Please don't worry about providing as much technical information as
> possible. I really want to understand this problem and will sincerely
> appreciate it all. Thanks, Lenny Stein.
>
>



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wrote:
> We bought this car with 90000 miles on it about a year ago. From the
> very beginning we started to notice a slight shudder when backing up.
> We took the car in to a friends place and he changed the blue fluid in
> the transfer case. He said that there was a problem with the All Wheel
> Drive function which affects the transfer cases on these and said "lets
> try the fluid change first and see if it helps". After doing the change
> there seemed to be little difference but eventually the problem seemed
> to all but dissappear. We were very encouraged. The car had been fine
> until recently when this transmission had lost reverse, which I am told
> is apparently a typical and unrelated problem with these. We had the
> trans rebuilt and it seems to be OK except for the fact that the slight
> shuddering problem in the drive train is now occurring again
> sporadically only in reverse, but not all the time when backing up.
> When it happens it seems to be worse if the wheels are turned but it it
> so intermittent that it is hard to say if the problem only occurrs when
> turning or it may occur when backing up in general. Like I said
> sometimes it doesn't happen at all. So far I have just never noticed it
> when straight backing up.
> So my questions a
> 1. What is happening here?
> 2. Did the original problem ruin reverse on the transmission and could
> this occurr again?
> 3. We don't really use 4WD. Can it be disabled thereby saving us a
> possible costly future repair again?
> 4. Might changing the blue fluid help again?
> 5. Is there a solution that will really "fix" this problem or is this
> just a poor design.
> Please don't worry about providing as much technical information as
> possible. I really want to understand this problem and will sincerely
> appreciate it all. Thanks, Lenny Stein.

=========
=========
"If", as yer post inplies, the symptom was not
there before the tranny rebuild..........

Be sure the tranny shop put "AutoTrac" fluid back in the T-case and
not regular Dextron 3.


Also....
I would ask them if they applied grease to the splines on the
driveshafts. One of the shafts "may" be binding under torque.

jest a thought.



~:~
MarshMonster
~:~

Is auto trak fluid something you add to and use in conjunction with
Dextron 3 (like the additive you use in a LSD or posi rear with 90W),
or is it something you use completely in place of Dextron 3. ?

wrote:
> Is auto trak fluid something you add to and use in conjunction with
> Dextron 3 (like the additive you use in a LSD or posi rear with 90W),
> or is it something you use completely in place of Dextron 3. ?

=========
=========

It's GMs designated lubricant for it's "clutch" driven trasnsfer case.



so....it's not used in conjunction with Dextron 3.
and...it's not used in place of Dextron 3.



It's used because it's the designated lubricant for the application.



~:~
MarshMonster
~:~

I asked him about that and he never touched the fluid in the Tcase. He
only rebuilt the transmission.

wrote:
> I asked him about that and he never touched the fluid in the Tcase. He
> only rebuilt the transmission.

========
========
Then you can tell him I said he was a half-assed tranny tech.




respectfully submitted
to address inferior workmanship


~:~
marshmonster
~wonders if that mechanic changes sparkplug wires but never
looks at the plugs~

Marsh Monster wrote:

> Then you can tell him I said he was a half-assed tranny tech.

Why?

Ian

shiden_kai wrote:
> Marsh Monster wrote:
>
> > Then you can tell him I said he was a half-assed tranny tech.
>
> Why?
>
> Ian

=========
=========

How did he know the fluid was good, or that it wasn't low, or that it
was the right type?


if he didn't mess with it....a little bit?




~:~
marsh

Marsh Monster wrote:

> How did he know the fluid was good, or that it wasn't low, or that it
> was the right type?
>
>
> if he didn't mess with it....a little bit?

I thought the OP said the tech said he
didn't touch the t/case fluid. Which is
quite possible, if you use something in
place of the rear driveshaft to keep the
fluid from leaking out while removing the
t/case. It's not necessary to drain and
fill the t/case when removing it to get at
the trans.

I know that I certainly wouldn't be fooling
around with the t/case if I was repairing the
transmission for no reverse. Pull the t/case
out, put it to the side and get on with repairing
the trans. I would check the t/case fluid level
when re-installing, that would be only prudent.

As another poster mentioned, there are bulletins
out that deal with the crowhopping issue. Replacing
a sensor in the encoder motor usually fixes the
problem on the AWD models.

Ian