97 tahoe, grinding noise

[SunlitComet]

Do I understand your to say that when you switch to 4x4 the noise goes away? If so when you replaced your t-case did you use the existing shift motor or a new one?

 

[nhbluevip]

I dont know if the grinding noise goes away when in 4x4, because I dont drive 60 to 75 MPH in 4x4. All I was saying was it goes into 4x4 fine. I dont know if the shift motor was replaced.

 

[SunlitComet]

you should be able to do highway in 4hi but not low if you don't want valves flying out of your hood like a sparkler. Just do it a short period of time on drive payment. Until you figured out the noise I would not shift on the fly at speed just yet. It maybe worth trying.


If the shift motor is the existing one my thought was something was wrong with its encode or the gearing inside causing a partial engagement. Just a thought.

If you have the nv243 t-case (RPO code NP1 I think-Check on the inside of your glove box face.) I have about 2 dozen papers on that system. Including T-case control module tech data. I can only fax it right now though.

 

[nhbluevip]

Good thought. The tranny and T-case were taken out of another 97 truck. So its a completely different tranny and t-case. The noise has not changed from the old tranny and t-case to the new one.

 

[nhbluevip]

I forgot to mention, the old tranny that was in it had a hair line crack in the case, just in front of the pan, which obviosly leaked bad and I believe burn out the tranny over time. Im thinking what ever this grinding vibration is, may have been what caused the crack before. I would like to figure this out, before it cracks another tranny or t-case.

 

[SunlitComet]

In that case it has got to be somewhere from the driveshafts outwards. Rings or pinions bearings or teeth - axle bearings. I do not know if a a malfunctioning locker could do it but maybe the front axle shift mechanism. Maybe something hitting the reluctor rings for ABS on the front wheels. Or maybe a plastic body piece hitting a moving part at speed. The sound is probably just traveling through the parts that will carry it the easiest. Can't think of much else unless you have it put on a rack with some one inside on the throttle.

 

[nhbluevip]

Agreed. I have had the rear end opened up to do the axle seals, all looked good. I agree it has to be something with the front, and vibrating the front axle? I don't understand why it woud go away the minute it is put into neatral, and your coasting?

 

[SunlitComet]

I forgot to mention, the old tranny that was in it had a hair line crack in the case, just in front of the pan, which obviosly leaked bad and I believe burn out the tranny over time. Im thinking what ever this grinding vibration is, may have been what caused the crack before. I would like to figure this out, before it cracks another tranny or t-case.

Is there any evidence that maybe a collision with parts has shifted the mounts on equipment cuasing binding problems. Page 98 of the document below might help if you want to do some basic measurements. There are more I just don't have them now.

http://www.sunlitcomet.com/pdf/auto/ck.pdf

---------- Post added at 06:18 PM ---------- Previous post was at 06:11 PM ----------

Agreed. I have had the rear end opened up to do the axle seals, all looked good. I agree it has to be something with the front, and vibrating the front axle? I don't understand why it woud go away the minute it is put into neatral, and your coasting?

Wear on the driving side of gear tooth or synchonizer face and none on the other face that makes contacts when coasting with no force.

Something like that.

 

[nhbluevip]

That could be. I know body work has been done to it at one point, and it has been painted.

 

[95TwinTT]

Was the old torque converter used with the newer trans?