2002 4.8L Auto Hard Shifting

StanTheMan · February 20, 2002

Have a new 2002 4.8L Seirra, 600 Miles. Latley, last 100 miles or so it has started shifting very hard from 1st to 2nd. Anyone else notice this? Normal? Or am I just being parinoid?

Stan....Dallas Tx.

CMNTMXR81 · February 20, 2002

No it shouldn't especially with the wonderful torque management feature in the PCM which scales back timing during shifts.

What I ask you do first may seem like I'm asking you to do something stupid and basic but I'm only asking it to make sure we have the basics covered. Have you checked the fluid level? If not, please do so. I remember reading somewhere (could've been here) where people were complaining of rough shifting and they were thinking something major was wrong only to find out that their new truck didn't have enough DexronIII in the trans.

Once we eliminate this, we can move on to other things.

StanTheMan · February 20, 2002

Fluid level is at the top of the "HOT" mark. Truck was 3/4 of a qt. low on trans fluid when I added Mobil 1 Syn. "Dextron III compatible". Hard shifting from 1st to 2nd started after I added trans. fluid.

Thanks for the suggestion though.

tigerfan9 · February 21, 2002

my 2000 5.3 GMC Sierra z71 is doing that same thing..... hard shifting between 1st and 2nd. I would really like to know what is causing this. you are not the only one....

StanTheMan · February 21, 2002

Hard shifting from 1st to 2nd has subsided for the moment.

On the way home from the office I selected tow haul for a few miles of stop and go driving. I noticed no change in the shift points.....none. Truck was shifting hard from 1st to 2nd as it had been for a 100 miles or so. So I turned it off the tow/ haul mode. No change in the shift points.....still shifting hard from 1st to 2nd. Drove for a while and stopped at a store, turned the truck off. Came out of the store and started the truck with tow / haul in the off position. The trans. shifted normally. Drove the long way home and trans shifted normally. Arrived home after dinner went out for a ride to see if I could figure out what was going on. Started out with out tow / haul. Trans shifted normally. Switched to tow / haul and the truck would rev and shift hard. Switched back and forth a few times and the trans was working normally. Computer glitch? Trans problem? We will see.

Stan.... Dallas Tx.

mnstrmdnss · February 21, 2002

your not the only one with the same problem! i have a 98 sonoma 2.2 with a 4l60E auto, and i have the same problem( shifting hard from 1st to 2nd). i recently hooked up a b+m electronic shift kit for firmer shifts, problably the same sort of setup you have, and after using the firmest seting for a while, i turned it off, and the tranny started to shift as smooth as glass! ive had mine at the dealership numerous times for this, and every time they would feed be the bull that nothing is wrong!! so, im guessing its more than likely that the problem lies in the tranny, where the computers cant detect the problem. anyway, mines under an extended warrenty, so if it goes out, oh well, im covered.

dannoj · January 3, 2004

I have the same problem with my 03 silverado. The dealer showed me a bulletin that said that this is normal and recommended no fixes should be attempted. I have 2.5 years to prove them wrong before my warranty expires.

DannoJ

silverado4800 · February 5, 2004

I feel your pain. I just posted about the shift shudder too, im still in the process of trying things to fix it, ill definitely post if i ever find a solution.

mikez · February 14, 2004

I have a 2003 GMC Sierra with the 5.3L and 4wd and have the same problem, but it doesn't do it all the time. Sometimes it will shift so hard that it will chirp the rear tires pretty good. I notice it the most when it is warm outside or the engine is @ operating temperature. The tire chirping is kind of cool, but I'm sure that this can't be good for the transmission. Also my problem occurs alot when I'm at about a 20mph roll in traffic going from first to second. Well I was getting really tired of the inconsistancy with the transmission shifting different all of the time, so I went to the dealer and requested for one of their good technicians to ride with me. The technician drove my truck with me riding along and during the drive we did not experience the hard 1-2 shift, imagine that, but I made him drive the truck as hard as he possibly could drive it and he admitted that the transmission was very sloppy and inconsistent. When we got back to the dealership he checked to see if their were any bulletins and there was one to replace a valve solenoid in the valve body. Sorry for the long story, but maybe this will allow some of you to determine if your problem is the same as mine and get it fixed.

silverado4800 · February 15, 2004

yeah i was under the impression it was my computer. every time i reset it it seemed to quick for a little while, but it is just coincidence, last time i reset it was shudding right afterwards. im leaning towards that solenoid valve too, ive heard alot about those things giving trouble from people from several forums. just like what the guy told u that drove ur truck, mine is sloppy and inconsistent. i guess ill get it fixed one day.

JDahl · March 16, 2004

Gm has had a real issue with the 1-2 shift. The 1/2 accumulator valve has a spring problem. It is either too stiff or too weak. The acumulator piston itself has issues with wear and problems with its springs also. When I built 4L60e's I would put a shift kit from transgo and that would generally make them shift like a dream. I do not like using the b/m transmission products. I don't believe they put enough research into their products.

John

ASE certified automatic and standard trans/transaxle technician

(until i decided to go back to school)

kwarrington · March 17, 2004

I have a 91 K2500 with 4L80E, does the same thing-1 to 2 hard shift. every other shift is nice and smooth. Harder the throttle at shift point, harder the shift. My ECM pulls up an 8-5 code, can't find any info for this code. Any help would be appreciated.

03Bowtie · March 18, 2004

I get an odd shift from 1st to 2nd, but it's not at WOT. If I am in traffic and start getting on the gas from a light, but then have to let off a little because of traffic ahead and it's ready to shift, it kind of does that shudder thing and feels like it's almost shifting back and forth for a split second. It does it so bad sometimes I'm afraid my tranny is gonna drop right onto the street. Any other time it is fine, smooth as silk, just when I am on the throttle then backing off right before the shift point...

mrtz71 · March 27, 2004

I bought my '02 Sierra new and it currently has 13,600 miles. I guess you could call it a shudder when it shifts from 1st to 2nd gear. It does not happen all the time, only on occasion. It never happens on initial acceleration from a stop or during other shift points.

It seems to happen more often after driving at least 30 minutes or longer. My daily drive to work is about 10 minutes and I have never experienced it then. In fact, when it is not having the problem, you couldn't ask for better shifting. But when it starts up, it will do it every 1st to 2nd gear shift.

I'll try to explain the shudder. Acceleration from a stop is normal but for one split second as it shifts into 2nd gear, there is a hesitation or brief delay. And then there is a loud thunk and the truck jumps forward. It's almost as if someone hit you from behind.

I had TSB 02-07-30-030 performed 10/16/03 and the problem has seemed to go away but has come back. Within the service information document it states temperature as a factor. I may have not noticed the problem again because of the cooler weather and my short driving characteristics.

Others must be having this problem since the TSB description is on the money. And it includes 2001-2003 Chevrolet Silverado and GMC Sierra with 4L60-E automatic transmission (RPO M30). It states the cause as a 12 Hz electrical feedback from the charging circuit "MAY" be affecting the transmission pressure control solenoid, causing a fluctuation of the line pressure within the transmission. However, it must not be a problem with all of these trucks since the service department is always surprised to hear of it and confused when trying to troubleshoot it. Could this be a problem that GM is hoping will be forgotten about with time?

Worktruck · March 28, 2004

I complained of a similar problem last fall on a 02 Sierra 4WD Ext cab w/ 4l60. I am pretty tight with the dealership where I bought my truck and there is a tech that lives across the road from me. Anyway I was told that the problem lies in the computers shift management, well not really a problem ata all. If the computer senses that the truck was rolling even the slightest bit in reverse when the trans is shifted into drive it will automatically go into abuse mode. Same goes for rolling forward when shifted into reverse. When in abuse mode the tranny shifts as if in tow haul. Made sense to me since I only have had a problem after plowing snow. Just my take on this.