Transmission bang

[Fishlips5dad]

I have a 2007 Silverado 2500HD classic body, 6.0L gas, 125K miles. Recently I noticed that after driving at freeway speed and then transitioning to surface streets, my transmission bangs from 1st to 2nd gear causing a transmission slip fault code. I changed the fluid and filter, flushed my transfer case fluid, still happens. Is there anything else I should look at before I dump a bunch of money getting my transmission rebuilt?

[Dnt]

No it is over, the transmission clutches are worn and it will have to be rebuilt. The electronic controls can compensate to a point but once the wear is really bad you will get the hard upshift. Unfortunately you killed it even sooner by changing the fluid. The new fluid contains acid type chemicals that will accelerate the wear process.

[Fishlips5dad]

So shutting the truck off when the bang is noticed only resets the electronic controls? I have also noticed that if I don't drive it on the freeway there is no banging or slipping of any kind. My wife informed me that she drove it about 20 miles, freeway and surface streets with no noticed banging. Is this a normal issue with these transmissions?

[Fishlips5dad]

I posted this in the wrong area at first but did get a response. So I have a 2007 Silverado 2500HD classic, 6.0L gas, 125K miles. When driving at freeway speed then transitioning to surface streets I notice a bang from 1st to 2nd. When I shut the truck off for a few minutes and start driving again, the bang is gone. This doesn't occur all the time. I have changed the fluid and filter (no shavings noticed) also changed the transfer case fluid. One suggestion is that I may have done more damage changing the fluid as the acid is going to speed up the clutch wear process and that a rebuild is most certainly in my future. Any help would be greatly appreciated.

[Dnt]

The trans could last another 100 miles or maybe 10,000 miles before she dies. I had a older model that banged into gear to the point where it barked the tires for 5 or 6000 miles before it finally gave up the ghost. (I never changed the fluid as I was warned against that) I did have to replace a UJoint that it snatched out with the hard upshift. A sure test is to see if the hard upshift lessens with a hard acceleration. If it hard upshifts only easy throttle to the point where you cringe knowing it is coming then you have the very common trans clutch wear problem. Not much you can do except start hunting down a deal on a good re-manufactured transmission. I have had a couple of them rebuilt in house at trans shops and they did OK (except for one a Georges transmission shop that blew the planetay gears 1 week after rebuild) but probably best to order up a re-manufactured trans from a reputable re-manufacturer. Lots of critical parts inside these things and really needs a person that does it EVERY day to make it right. Do Not even think about attempting to rebuild yourself you will regret that decision LOL (been there got the tshirt)

[casey.mikl]

Is it a bang? Or is it shifting firm? Also changing the fluid isn't going to damage the transmission. A simple filter change and new fluid isn't going to hurt it. If you have it flushed, and it's never been flushed before, that will hurt it. When you flush, all of the fluid is changed. When you drop the pan and Chang the filter, then refill. Your only adding a few quarts in to refill it. Those new quarts of fluid mix with the old fluid. And won't hurt the trans.

 

 

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[davester]

Unless you are filling the transmission with acid instead of transmission fluid, changing the fluid isn't going to noticeably shorten the lifespan of any of the transmission components.

 

It's transmission flushes that can hurt your transmission, as they can cause sediment/bits that are trapped in various crevices to break free and wreak havoc.

 

No idea what's causing that bang.

[Formulabruce]

Change the 1-2 shift solenoid, re-use the ORIGINAL thick metal reinforced pan gasket, if you tossed it, get a new one from a GM dealership. Cost about 35 bucks without the gasket . Easy install from underside.

[Fishlips5dad]

I did not do a complete flush. New filter after dropping the pan and refilled to spec. I did use the original gasket as the flimsy one provided as a replacement was not something I was willing to use. The shifting seems to be hard, no noticable rpm jump. My wife drove it the other day and reported no banging at all. I appreciate all the feed back. I'll take it out this weekend when I get back into town and report my findings. Hopefully it is an easy fix.

[Raptordude]

I think that's an electronic problem, if it were the clutches it would be doing it all the time. I don't think you need a rebuild, but electrical problems can be a pain to chase

 

 

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[Dnt]

Sorry but I am not going to sugar coat I have seen this at least a dozen times with our 3/4 ton company trucks. It is very possible that a solenoid is now bad BECAUSE the clutch wear has dumped all kinds of debris into the fluid. You MIGHT have 10,000 miles left but probably a lot less. No way I would take this on a long trip hauling a heavy load or towing a trailer unless I had a wrecker service on speed dial. Good Luck man.

[Dixon700]

I don't think you guys are giving the 4l80e enough credit. Mine has 220k mi on it and wasn't necessarily taken care of. the entire truck was beat pretty hard and I had to rebuild the transfer case when I got it due to pump rubbing though the case and there was no oil in the case. So I'd get a quality scanner and do some electronic diagnosis and it may just be a bum solenoid.

[Dnt]

Well a lot of trucks are not abused but you just never know what has happened to a vehicle if you buy used....assuming the OP bought a used truck?

[Fishlips5dad]

I bought my truck brand new, had 8 miles on it when I drove it off the lot. Did everything I was supposed to do maintenance wise. Only thing up till now that shit the bed was left hub bearing. $90 and about 30 minutes of a friend of mines time and I was all good.

[C/K Man]

This newer transmissions have adaptive strategy. That means the PCM can compensate for some issues. One issue is a slipping clutch, which the PCM can compensate for by raising line pressure to get the clutch to grab tighter. High line pressure will result in a very firm shift, so it is possible that you do have one or more worn clutches and the PCM is responding to the condition. There are a couple of other problems that can cause firm or late shifting, but since you say you do have a code for a slip it sounds like that is what is happening. It's not that the firm shift is causing the slip DTC, it's the slip is actually causing the firm shift. Solenoid problems usually have their own DTC's, so it is probably less likely you have a solenoid problem.

 

Good diagnosis is not just looking at DTC's. By using a scanner (not a code reader) and reading the data stream while the vehicle is being driven, a good transmission tech. can see exactly what is happening. He can monitor clutches for slipping and see if the PCM is commanding high line pressure to compensate. Or see shift solenoids that are hanging up causing a delay from when the PCM commands a shift and when it actually happens.

 

If you do in fact have a slipping clutch, best thing to do is get the transmission rebuilt or exchange for a reman. unit. Too much labor to replace one internal component, better off replacing or rebuilding if you have over 100,000 miles on it. I have had very good luck with the G.M. 'factory' remans..

 

Best of luck to you.