odd sound.....4 wheel drive problem?

[zachzchw]

Driving on quite a long trip the other day, noticed something new on my 97. (Seems like theres always something.) When Im at a dead stop, if I accelerate slowly, it feel like your going over small speed bumps that are close together. You can feel it in your back through the seat. Tires are all fine.
Im wondering if its some new parts "breaking in" as I recently had a pitman arm and idler arm replaced.
Any thoughts?

[Chris Stewart]

Sorry for being late, I couldn't get the post to show yesterday.
Do you feel the bumps if you pull straight ahead or do you have to make a turn after the stop?

[zachzchw]

Straight ahead.....
Ive had the car in my garage since then (last wednesday) and got it out to try to feel it again, so I could describe it better. Of course, it didnt do it.
Not sure if the following is related or not: When I first got it out of the garage, as I shift between reverse/drive, it sort of lurches a little bit after Im done moving the shift knob. Is that just natural due to the weight of the vehicle?

[ericn1300]

could be a U joint on the drive shaft gone bad. try keeping your foot on the brake as you shift back and forth from reverse to drive. if you get a clunking noise on the gear reversal put the vehicle in park and set the parking brake. go under to see if you can rotate the drive shaft by hand. even a little movement in rotation indicates a problem. should feel sound with little movement.

[Chris Stewart]

Does it feel like the transmission is a little late before sliding into the forward gear? It could be cold transmission fluid, but the "bumps you indicated could be related if the "bumps" were the transmission clutches shuddering. This problem should show up as a Check Engine light with a transmission trouble code. How long since the transmission fluid & filter change?

[zachzchw]

Eric- just had u joints done about six months ago. Probaly less than 8000 miles on them. Hopefully they arent going again already!
Chris- no check engine lights are on. Ill have the tranny fluid changed as soon as I can.

Odd thing is, I tried it again yesterday- didnt do it at all. Hopefully it stays that way.

[ericn1300]

how cold was it when you noticed the problem. very cold tires stay out of round and tend to hold the flat spot from where they were parked until they heat up after a mile or so, giving you a weird thumping like hitting speed bumps when the flat side comes around. and when the flat spots get out of sequence, such as when you turn out of the driveway, it sometimes creates a little wobble in the steering wheel. the wobble may not be noticable to the touch with the soft power steering on the Bravadas, but let go of the steering wheel and watch for it.

[zachzchw]

Originally Posted by ericn1300

how cold was it when you noticed the problem. very cold tires stay out of round and tend to hold the flat spot from where they were parked until they heat up after a mile or so, giving you a weird thumping like hitting speed bumps when the flat side comes around. and when the flat spots get out of sequence, such as when you turn out of the driveway, it sometimes creates a little wobble in the steering wheel. the wobble may not be noticable to the touch with the soft power steering on the Bravadas, but let go of the steering wheel and watch for it.

The first time I noticed it, it was probably halfway on the 200 mile trip.

[ericn1300]

the front end work you had done shouldn't cause these symptoms. since the problem showed up when as my daddy would put it "the pony was hot and wet". i have to agree with Chris. probably a cooling problem caused by old or low tranny fluid or contamination. also check the front end, the radiator cowl and grill area may have a build up of leaves and other debris inhibiting air flow.

[zachzchw]

Originally Posted by ericn1300

the front end work you had done shouldn't cause these symptoms. since the problem showed up when as my daddy would put it "the pony was hot and wet". i have to agree with Chris. probably a cooling problem caused by old or low tranny fluid or contamination. also check the front end, the radiator cowl and grill area may have a build up of leaves and other debris inhibiting air flow.

Yep, there are leaves and crap in the grill area. Ill clean those out, and get the tranny fluid changed.
Thanks a lot to both of you for your help, much appreciated!!

[Toolwise]

Well, I thought my 94 was having the same problem as you described, but I only noticed it on the freeway when traffic was bogged down and speed was only about 20 mph. But, I soon noticed both cars infront of me seemed to be hopping while I was stopped and he began to accelerate. So it was just that patchy of the freeway. So maybe thats what you experienced, because I know that in my neighborhood and everywhere else I haven't experienced the bumps.

[Chris Stewart]

I was stopped with my back tires on a 300ft. bridge and the front tires on the ...uhhh....riverbank, I don't know what you call the joint where the bridge meets the riverbank. Anyway the front tires were sitting solid but the back wheels being on the bridge..bounced. If fact it was bouncing hard enough for the sqeaky shocks to start sqeaking, kinda scared me at first until I realized what was going on. :22yikes: