Jump to content

Archived

This topic is now archived and is closed to further replies.

Recommended Posts

I've noticed since about early summer I've had a jerky, rough shift from 1st to 2nd gear in my 2007 GMT900 Silverado. It's not always real rough. If I flat out floor it or I make a long, lazy take off from a stop it jerks pretty hard. However, if I lay into the accelerator, not too hard, but nothing easy either, it is barely noticable. I've experimented with it a little and drove up a steep hill next to home. I pulled the gear down into 1 rather than D and got the truck moving to about 2500RPMs and 20mph. Then I let off the gas and put her into 2 and there's a slight lull then a semi-loud "clank" sound (with windows down) and then the jerk. It doesn't do it in any other gear change.

 

Now, I remember reading on here that people like silky smooth shifting so auto manufacturers make them that way but that the silky smooth shifts are harder on a transmission than a rough shift. Is this true? If so should I just let the rough shifting be and drive it like normal? I don't mind the shift...I kinda like a rough ride in a pick-up :D . However, if it's damaging or harmful to the truck I'd rather it fixed. Should I let the dealer see it or try some of the "rough shift fix" solvents out there first?

 

Thanks.

Share this post


Link to post
Share on other sites

By the way it's a 4.8L V8 if that makes any difference. I bought the truck off the lot with 33 miles in late May of '07 and I know it didn't do this prior to this past spring. I've been doing a little research on it and I've seen one solution is to disconnect the battery overnight to let the computer reset "shift adapts" in the PCM.

 

I'm not sure whether I want to try this yet or not. Again, if the hard shifting isn't hurting anything and is actually easier on the transmission than smooth shifts I'd sooner leave it alone. But until that is proven I'm gonna stay a little wary of it.

 

If I did disconnect the battery tonight how long does it have to be connected for in the morning to fire up? Right away or is there some time for it to "recharge"?

Share this post


Link to post
Share on other sites

I can't really comment on the shifting issue, outside of my experience. But to me when the tranny goes clank, it's not a good thing.

 

On the battery reconnect, as far as I have ever heard, just connect it up and you should be good to go.

Share this post


Link to post
Share on other sites
However, if it's damaging or harmful to the truck I'd rather it fixed. Should I let the dealer see it or try some of the "rough shift fix" solvents out there first?

If its under warranty, let the dealer mess with it. Please, not for any reason put any of the snake oils in the transmission.

How many miles do you have? Any check engine light? Also, check the color of the fluid, it should be nice aand pink.

Share this post


Link to post
Share on other sites

I had the same problem with my '99 Sierra (gmt800) with a 4.8 and it turned out to be a sticking servo in the trans. I too would unhook the battery for about 30 min and reconnect and the problem would go away for awhile. But if its under warranty let the dealer fix it !!

Share this post


Link to post
Share on other sites

I got exactly 12,880 miles right now. No check engine light that I've seen. I'll check the fluid color tomorrow but I reckon last time I saw it, it was as pink as could be.

 

Waterboy: When you reconnected the battery would the hard shift come back eventually?

 

 

Should I expect any different noises or actions if I disconnect the battery all night and reconnect it in the morning since the computer will have to relearn everything? Also, it's 38 degrees here now; I wouldn't think there would be a problem if the battery is unhooked overnight and it dips below freezing but I want to be sure first.....I got the green light?

Share this post


Link to post
Share on other sites
I got exactly 12,880 miles right now. No check engine light that I've seen. I'll check the fluid color tomorrow but I reckon last time I saw it, it was as pink as could be.

 

Waterboy: When you reconnected the battery would the hard shift come back eventually?

 

 

Should I expect any different noises or actions if I disconnect the battery all night and reconnect it in the morning since the computer will have to relearn everything? Also, it's 38 degrees here now; I wouldn't think there would be a problem if the battery is unhooked overnight and it dips below freezing but I want to be sure first.....I got the green light?

 

The hard shift would come back eventually. Could never predict when. With such low mileage (12,880) I certainly would not hesitate to bring your truck in to your dealer and let them check it out. Thats the best part of buying a new truck, not having to fix it!! I would be interested to know what they discover to be the problem .

Share this post


Link to post
Share on other sites

I had my truck in for service this morning and mentioned the rough shifting. After about 2.5 hours of walking around the service department guy tells me that I'm all done and the transmission guy looked at the rough shifting. He said they test drove it and updated the computer with the latest shift adapts. He said the shift has softened some but that it's still there somewhat. He told me then to take it home and drive it for a while to see if it eventually softens out. If it doesn't however, I'm supposed to bring it back so they can check the valve body which might take 1-2 days.

 

Also, I'm not sure if it has anything to do with it but my transmission fluid was marked as being low. They didn't mark down on the paper whether they filled it or not so I did a hot check when I got home and it looks OK I think. I assume they filled it. I shouldn't have low transmission fluid at only 13,200 miles though.

 

Anyway, on the way home I couldn't notice any difference in the rough shifting. I actually thought it might have gotten worse now. I suppose I'll drive it for a week or so and if nothing changes I'll have the valve body checked out.

 

Any suggestions?

Share this post


Link to post
Share on other sites

to your question about smooth vs rough shifts and good or bad for the trans...it's been my experience that rough to a complain level is probably OK for clutch plates, but it puts a heck of a spike on the drivetrain and is not so good for those parts. Too smooth is easy on the drivetrain, but harder on clutches in the trans (slipping too long before they grab the next gear). It's my understanding that most of the electronicly controlled transmissions have 'adapts' to make sure the shift isn't too 'slippy' as to cause a clutch problem, but that they not too harsh, either....a nice happy balance. :(

 

It doesn't sound like you have a happy balance. If the new flash doens't get you the balance soon (in a day or 2 of driving tops), I'd get it back in before you hurt something else that won't fail 'til you're miles from the dealer and are late for something important.

Share this post


Link to post
Share on other sites

OK, sound good. If the new flash doesn't balance me out and they look at the valve body and fix it would they be able to find any damage to the drivetrain if present? That should still be covered under warranty correct?

 

It's probably been doing this since June of this year. Hopefully 6 months like that ain't too hard on it.

Share this post


Link to post
Share on other sites

By 'not so good for those parts', I meant that it'd cause accelerated wear, not a catastrophic failure or "big" damage. Example: Prop shaft U-Joints would wear quicker with big spikes than without them so that they would be junkola at 100000 miles rather than 125000 miles. Towing a trailer all the time will do similar stuff, but unlike 'not normal' harsh shift feel, trailering is supposed to be comprehended in the testing that the manuf. does to make sure that, assuming good parts from the start, all is good and durable. Unless your harsh shift was REALLY obnoxious, it's VERY UNLIKELY that 6 months of exposure to this shift would have hurt something to the point where a dealer tech. could detect it.

Share this post


Link to post
Share on other sites

If you figure out whats wrong please lets us know. I have an 2007 with a similar problem. My truck seems to hang in 1st too long and then shifts into 2nd rough. Its really annoying. It happens most often when driving in my neighborhood. I slow down to make a turn and then get on the gas and its just not handling everything smoothly.

Share this post


Link to post
Share on other sites

I'm scheduled in next Tuesday. I'll let yall know what I find out. They're supposed to be looking at the valve body for the problem. Hopefully they find something.

Share this post


Link to post
Share on other sites

hey, please keep me posted too on the rough shifting. i get the rough shifting alot of mornings while driving down my street. i also get a clink noise while my truck shifts into 2nd or vice versa into 1st and sometimes from 3rd into 2nd gear. the dealer told me my noises and hard shifting is "normal"

thanks

Travis

Share this post


Link to post
Share on other sites

Wow, this is more common than I thought. My 2007 Silverado Classic (14,700 miles) does the same. My shift from 1st to 2nd is rough occasionally. It seems very unpredictable though, I think it depends on how my foot is on the pedal. I noticed it is more frequent when the it's cold.

Share this post


Link to post
Share on other sites

  • Popular Now

×

Important Information

By using this site, you agree to our Terms of Use.