99 Silverado shifting problem

04HEMIRAM · 02-13-2007, 08:04 PM

I have a 99 Silverado with a 5.3l engine that has a shifting problem. If I drive a while at speeds under 55 mph, stop at a light and take off again, it shifts so hard from 1st to 2nd it seems like the tranny is going to fall out from under the truck. The service engine soon light is on also. I have taken it and had it hooked up to the computer and it says that something is slipping in the transmission. They can clear the code and its fine for a while but eventually comes back. When it happens, I can stop and shut the vehicle off for a couple of minutes and it seems to go away. Maybe I'm wrong, but seems to be an electrical problem, otherwise it wouldn't go away. I'm not a mechanic though!

Has anyone had this sort of problem or know anybody who has that can help.

I should also mention that is a 4x4 with 70,000 miles if that makes a difference.

bradrhale · 02-14-2007, 11:50 AM

which code does it throw. list the number so that we might have an idea what is actually going on.

joshnkelly · 02-14-2007, 01:20 PM

I had a truck do the same thing and could not figure it out. Someone told me to change the transmission fluid and see what that did. So I did and the truck ran fine. Hope this helps.

04HEMIRAM · 02-14-2007, 06:22 PM

I'm not sure what the code was. The mechanic just said that it stated that there was something slipping in the transmission. He told me to take it to a transmission shop. I should have mentioned that I have already serviced the transmission and it didn't help. Here is something weird- It is about an 8 mile drive to town from here and if I take the back highway that has a speed limit of 55, the first stop light I come to and stop, when I take off it shifts hard. If I take the main highway, with a speed limit of 65, it will never do it. I can run around town all day and never have a problem. If I take the back highway home, as soon as I stop and take off again it shifts hard. Does that make any sense at all?

gmtech · 02-14-2007, 06:46 PM

The computor in your truck is capible of adjusting transmission pressures to adjust for slipage. So if while driving it watches every shift 1-2 2-3 etc and watches the timing of the shifts and it can boost pressure to adjust. When you drive at 55 on your trip instead of 65 it could just be that it is not picking up the slip while in lock up as much at the higher speed as the lower speed. By clearing the codes all the shift adapts as they are called are erased and has to be driven for the computor to reboost the pressures to adjust for the slipping.That is why when you take off from a stop with higher transmission pressure it acts like it has a shift kit and shifts very firm. It is trying very hard to hold pressure wihtin whatever clutch pack is slipping or causing a loss of pressure. With that all said you need to bring it to a transmission shop or dealer to determine the cause of the internal slipping and causing the p1870 trans component slipping code or it will leave you stranded.

04HEMIRAM · 02-14-2007, 07:10 PM

That seems to make a lot of sense. I will get it to a transmission shop. I've always thought that it was an electrical problem. Is this going to cost me a butt load? Would it be cheaper to put in a re-manufactured tranny? Let me know and thanks a lot for the help.

gmtech · 02-14-2007, 07:45 PM

Its hard to say what it needs but most of your trans shops like AAMCO do free inspections and quotes. Reman at a dealer run around 1500-2000 plus 6-8hrs labor but do carry a 3year 100k mile full warrnty parts and labor.

04HEMIRAM · 02-14-2007, 08:24 PM

Well that is a butt load. I guess I will start with the tranny shop. I have never put a transmission in a newer truck, is that much different than an older one?

mrjohnwayne · 02-15-2007, 08:09 AM

nope. Not much different at all.

02-13-2007, 08:04 PM	#1
04HEMIRAM Full Member Join Date: Feb 2007 Location: Iowa Posts: 12	99 Silverado shifting problem I have a 99 Silverado with a 5.3l engine that has a shifting problem. If I drive a while at speeds under 55 mph, stop at a light and take off again, it shifts so hard from 1st to 2nd it seems like the tranny is going to fall out from under the truck. The service engine soon light is on also. I have taken it and had it hooked up to the computer and it says that something is slipping in the transmission. They can clear the code and its fine for a while but eventually comes back. When it happens, I can stop and shut the vehicle off for a couple of minutes and it seems to go away. Maybe I'm wrong, but seems to be an electrical problem, otherwise it wouldn't go away. I'm not a mechanic though! Has anyone had this sort of problem or know anybody who has that can help. I should also mention that is a 4x4 with 70,000 miles if that makes a difference. Last edited by 04HEMIRAM; 02-13-2007 at 09:24 PM.

02-15-2007, 08:09 AM	#9
mrjohnwayne Moderator Join Date: Apr 2005 Location: Texas Posts: 3,220	nope. Not much different at all. __________________ John Wayne 2000 F-350 7.3L Powerstroke 4x4

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02-14-2007, 11:50 AM	#2
bradrhale Moderator Join Date: Apr 2006 Location: Texas Posts: 3,609	which code does it throw. list the number so that we might have an idea what is actually going on.

02-14-2007, 01:20 PM	#3
joshnkelly Full Member Join Date: Nov 2006 Posts: 17	I had a truck do the same thing and could not figure it out. Someone told me to change the transmission fluid and see what that did. So I did and the truck ran fine. Hope this helps.

02-14-2007, 06:22 PM	#4
04HEMIRAM Full Member Join Date: Feb 2007 Location: Iowa Posts: 12	I'm not sure what the code was. The mechanic just said that it stated that there was something slipping in the transmission. He told me to take it to a transmission shop. I should have mentioned that I have already serviced the transmission and it didn't help. Here is something weird- It is about an 8 mile drive to town from here and if I take the back highway that has a speed limit of 55, the first stop light I come to and stop, when I take off it shifts hard. If I take the main highway, with a speed limit of 65, it will never do it. I can run around town all day and never have a problem. If I take the back highway home, as soon as I stop and take off again it shifts hard. Does that make any sense at all?

02-14-2007, 06:46 PM	#5
gmtech Senior Member Join Date: Dec 2005 Location: farmville Va Posts: 348	The computor in your truck is capible of adjusting transmission pressures to adjust for slipage. So if while driving it watches every shift 1-2 2-3 etc and watches the timing of the shifts and it can boost pressure to adjust. When you drive at 55 on your trip instead of 65 it could just be that it is not picking up the slip while in lock up as much at the higher speed as the lower speed. By clearing the codes all the shift adapts as they are called are erased and has to be driven for the computor to reboost the pressures to adjust for the slipping.That is why when you take off from a stop with higher transmission pressure it acts like it has a shift kit and shifts very firm. It is trying very hard to hold pressure wihtin whatever clutch pack is slipping or causing a loss of pressure. With that all said you need to bring it to a transmission shop or dealer to determine the cause of the internal slipping and causing the p1870 trans component slipping code or it will leave you stranded.

02-14-2007, 07:10 PM	#6
04HEMIRAM Full Member Join Date: Feb 2007 Location: Iowa Posts: 12	That seems to make a lot of sense. I will get it to a transmission shop. I've always thought that it was an electrical problem. Is this going to cost me a butt load? Would it be cheaper to put in a re-manufactured tranny? Let me know and thanks a lot for the help.

02-14-2007, 07:45 PM	#7
gmtech Senior Member Join Date: Dec 2005 Location: farmville Va Posts: 348	Its hard to say what it needs but most of your trans shops like AAMCO do free inspections and quotes. Reman at a dealer run around 1500-2000 plus 6-8hrs labor but do carry a 3year 100k mile full warrnty parts and labor.

02-14-2007, 08:24 PM	#8
04HEMIRAM Full Member Join Date: Feb 2007 Location: Iowa Posts: 12	Well that is a butt load. I guess I will start with the tranny shop. I have never put a transmission in a newer truck, is that much different than an older one?