? Rattle and Slipping Tranny ?

[smills4635]

Hi all. My husband slid out on black ice a few weeks ago and slammed into a guard rail with the front rider side corner. It took out the front bumper and messed up the headlight case and front corner panel. We were out of state had two mechanics look at it before we drove it 400 miles home, one a Chevy mechanic and one a local guy. Both said it looked fine to drive. It's popping a cracking from up there but that's not surprising. Once home, he put it in 4wd and it's making a grinding sound. I drove it the other day and it felt like it was stuck in 4wd when in 2. I clicked the 4hi and then back to 2 and it seemed OK. Our son got under there today and he says the cv joint feels loose and he thinks the sound is coming from the transfer case. Can anyone give me their opinion and any suggestions as to what and how to check? We're trying to decide whether to sink more money into it or look for another truck. It's got over 200,000 miles on it but it's been a great truck and we had no problems till this happened. Thanks in advance for any help!

 

[SunlitComet]

So it is working fine now or is it still doing something wrong? And what 4wd do you have?

 

[smills4635]

It runs OK in 2wd, tho it seemed to slip into 4wd on it's own that one time and then back into 2 when I switched them back and forth, and to me it feels like it's having a hard time engaging at all sometimes: it acts like it doesn't want to back up without me giving it gas. I've tried not to drive it any more than I have to since then. When you say what kind, I'm not sure exactly what you mean, but I can tell you it's a 1998 350 4wd and it has an auto 4wd option. Does that help? :/

 

[SunlitComet]

So you have the NP-8 NV-246 auto 4wd t-case then. Does the reverse problem happen in 2wd or 4wd? And when it slipped into 4wd was auto4wd mode selected?

 

[smills4635]

When it seemed to slip on me it was just after the reverse didn't want to work in 2wd. I was backing out of the driveway in 2wd and it felt like it wouldn't go, then when I put it into drive, 2wd, it felt like it was in 4wd as I went forward. It did that jumping thing like it does if you're in 4 on dry pavement. It was in 2 right then. I stopped and hit 4hi then back to 2 and it was OK after that. Like it was stuck for a minute.

---------- Post added at 02:36 AM ---------- Previous post was at 02:31 AM ----------

I said it sounds like a grinding noise when you put it in 4, my husband said it sounds like you're dragging something underneath when you put it in 4. He drives it way more than I do, so he would know better than I do. I'm thinking something went wonky with the transfer case or the drive shaft when he hit the rail.

 

[SunlitComet]

Can you be absolutely sure that you can select each mode manually (leave auto out of the equation for now) and that it will function in drive for at least one minute at various driving speeds with no glitches. If things start acting weird, I would gather something is wrong with the internal t-case, clutch, a clutch pack in the tranny is slipping, the sunshell in the tranny just happened by chance to get damaged somehow or the front axle is locked in 4wd when it should not be and maybe fighting with the t-case gearing or its clutch. Tranny is full of dexron 3 (red colored) and t-case of autotrac 2 fluid (blue colored)?