99 Silverado Transmission Woes.

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#1
Year: 1999
Make: Chevrolet
Model: Silverado LS Z-71
Engine Size: 5.3

Hey Guys,

My truck is presenting early signs of transmission wear I think. Here is the situation, when accelerating from a stop it feels as if the transmission is slipping occasionally. The engine will rev and then the tranny catches and away we go. This initial slip is the only time it happens and it does not do it at every stop. This is normal acceleration, not road racing by any means. My question is this, I have had a leaky output shaft seal no the transfer case for a few months now and I just haven't had the time to replace it. If the transfer case gets low, could it be causing this slip that I have described? Or am I looking at two separate issues here? Also, is there anything short of replacing the tranny that could be done to remedy this situation? Of course I will try to install my new seal on the transfer case asap. Any suggestions or ideas are very welcome and appreciated. Thanks,

Josh
 
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#2
might get better fesponse in TRANSMISSION forum....will see if moderator can move

would be helpful to know..
is service engine light on?
fluid level for transmissin is good?
Any modifications, add on or aftermarket parts?

As a first suggestion transmission filter change when doing that seal.
 
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#3
Thanks for the quick response.

1. Service engine light is on, it has been on and off for some time now. It has been a fuel system code that is setting it, however I have not checked it for the most recent activity in the past month.

2. Fluid level in the transmission is good, it does not change even though the transfer case is leaking. I believe these two do not share a reservoir on this vehicle.

3. No modifications or aftermarket parts associated with the transmission, I did change the fluid approximately 8 months ago. At this time I replaced the transmission filter as well. Sorry about posting in the wrong forum, this is my first visit since the forums were upgraded.
 
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#4
I asked moderator to move hoping one of the trans guru's would see it, asked the easy questions to get them thinking

Definately get the codes- be sure scanner is transmission code capable
fluid is good :) seperate BUT migration can occor
 
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#5
Right on with the codes, P0753. Looks like a shift solenoid may be going. Is this something I can do myself, or are there other possibilities? Thanks, any suggestions are appreciated.

Josh
 
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#6
If that is the problem it is a piece of cake to replace it.
Remove the pan and swap it out.
But.
Codes do not say replace the part .
They say check it out .
Here is the flow chart for that code.
Go threw it to see what the problem is.
http://members.troublecodes.net/crunch/753nt.pdf
 
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#7
OK, I don't have the jumper cable that the procedure calls for. Is it absolutely neccesary or can it be done without it? Thanks

Josh
 

Transman

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#8
The jumper harness is a nice luxury, we do this work every day and I don't have every jumper set there is. There are just too many to count. The thing you need to check for aside from following the tree here is look for bent or loose pins inside the connector, it is very common for pins to jump out even if they look like they are where they belong. They can fool you because when you disconnect the connector friction will pull the pins back into their proper place until you re-connect the connector. Gently use your finger and a light to push the pins from the inside and feel if any can be pushed out or back, please remember I said gently as they bend very easily.
Solenoids are fairly common on these trannys, drop the pan and look at them, take an ohm meter and ohm them out. If they are out of spec then replace them.
It never hurts to examine connections of other components too, the "Range Mode switch" (neutral switch) is a very common problem and will cause many bogus codes. Look for bad grounds on the engine especially at the battery, corrosion is a big problem and today's computers do not like extra resistance or voltage at all. You have to watch the charging system on today's cars also, we have had many "bad transmissions" simply turn out to be an alternator that was throwing too much ac current into the mix. We had one last week that the dealer told the customer his trans was shot, we diagnosed the system and replaced the defective alternator...trans problem gone. Transman
 
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#9
OK, I have an additional symptom now. Today on my way back from Dallas to Tulsa, my truck did not want to stay in overdrive. It felt and looked like a slip, but there were no new codes when I got home. The truck felt like it was surging and the tach would climb from 2.5K to 3 or 3.2K. The tranny fluid and filter were changed approximately 30K miles ago, and it seems to me like it is pretty burned and discolored. I can see red in it, but it is more like a molasses color than a cherry red. I plan to take it into a transmission shop, but I want to check with you guys so that I may have an idea of what to expect to hear. Thank you for your responses so far, they are appreciated. I just haven't had time to check these things out.

Josh
 

Transman

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#10
It is hard to give you more advise when the info requested has not returned except for more symptoms. The way you described the last symptom sounds more like an engine problem than a tranny problem. When was your last tune-up? any additions, remote start, air filter, alarm system, etc.? The fluid changing color is indicating high temps inside the trans and needs to be dealt with pronto. It may be slipping which will raise the trans temp and discolor the fluid also. There are just too many directions to go at this point to be of any real value to you. Transman
 
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#11
Regarding the electrical, how is the computer suppose to detect an error with the neutral safety or brake switch if there is no other switches of this type to compare to? Same with the electrical connector and even the ignition switch. Computer doesn't know if the ignition switch is on or off, what gear you are in, or whether you are stepping on the brake switch or not, it just responds to whatever signals it receives. Do not depend on codes, codes only exist when a parameter can be compared to even with other parameters. That has to be checked manually. Had the same problems you are having and found very green unplated bare copper switch contacts, cleaned those and many problems went away.
 
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#12
It is raining right now, I will try to crawl under the truck this afternoon when I get home from work and check the electrical connections. I will also print out the document posted earlier and try to run through those scenarios. Can you please describe general location of the connectors and parts that have been mentioned above? It will help me if I have a general idea of what I am looking for. Thanks again, I will post back with what I find if this rain lets up.

Josh
 

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#13
Once you've dropped the pan, the 1-2 and 2-3 shift solenoids are next to each other on the back side of the valve body. The 1-2 is closest to the driver's side and the 2-3 closest to the passenger's side. Post a listing of all codes, if you can. A faulty ignition switch can't be ruled out at this point. If your symptoms appear to be 2nd and 3rd gear only, the problem likely lies in the 1-2 SS circuit. Also, the solenoids can be bench tested to verify electrical integrity, as well as their ability to open and close properly.
 
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#14
OK, I had to take this truck into the shop yesterday. When I left work it was very jerky at low speeds. I could sit at a stop light and the truck would try to lurch forward, I could hear it knocking in the tranny. I knew the tranny fluid was pretty dark and burned smelling, but the mechanic at the shop said he had never seen any that black. He said it resembled diesel oil after about 20000 miles. Anyway, they replaced the 1-2 and 3-4 shift solonoid and put a filter kit in it. I am not in a position to rebuild the transmission right now so this cheaper avenue was good for me for now. It was much smoother today after I picked it up and it ran very well all the way home. Thanks to you all for your suggestions, I simply did not have the time to deal with this on my own and I needed it back in short time so I had to break down and take it in. Thanks again,

Josh
 

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#15
We understand the problems in fixing it yourself and lots of people that do this have the time and patience to give it a whirl. Reality steps in and sometimes makes us aware of time limitations and even sometimes personal limitations making us aware that a pro is the best action. Regardless of your individual reality in this case, you went in more informed of what might be needed and if BS on a shovel came your way you would have been prepared and able to spot it coming in time to step out of the way. I do however, doubt that this tranny guy has never seen fluid as black as yours. I have seen fluid so black and thick that it was like pure coal tar, I removed a pan on one trans that was so nasty that the imprint of the valve body was inside the goo in the pan. Glad you posted back and good luck with the repairs, Transman