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Discussion Starter · #1 ·
I changed my tranny fluid and filter several months ago with any problems for a long time until recently. No when my car is fully warm and I am driving around the city, I notice a very hard, fast shift. I don't feel any gears not meshing but the shift is very tight and actually jerks the car forward a bit. I can't see how it could be too much fluid since I've gone this long without a problem (around 3 months). I don't see too little fluid when it's just idling, but I do see bubbles in the fluid when I pull over when it's happening. This means to me I am sloshing around too much fluid and pushing air on the gears instead of fluid.... Or is this a computer problem? I don't see any metal shavings in the bubbles that would cause them.

Any help would be appreciated. It's a 1998 4T65E.
 

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Howdy all,


I would first check for codes. Many trans codes will cause line pressure to max due to defaut status. secondly, with fluid getting bubbles whipped into it indicates an air leak somewhere such as a loose filter of cracked filter.

Big Jeff
 

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Discussion Starter · #3 ·
I was actually thinking that, so you think it is a possibility that my filter has a problem or has (fallen out) or maybe the gasket that seals it is bad??? I think I'm going to open her up and take a look again because I'm starting to get tired of not knowing...
 

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I would try the scan first before opening it up. "I" misprogrammed :eek: a point on HP tuner and got a similar problem. There was a code in the computer causing it but it was one that did not give an SES light.
 

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Discussion Starter · #5 ·
This is a stock PCM though, even still ill have the codes read.
 

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magilson said:
I changed my tranny fluid and filter several months ago with any problems for a long time until recently. No when my car is fully warm and I am driving around the city, I notice a very hard, fast shift. I don't feel any gears not meshing but the shift is very tight and actually jerks the car forward a bit. I can't see how it could be too much fluid since I've gone this long without a problem (around 3 months). I don't see too little fluid when it's just idling, but I do see bubbles in the fluid when I pull over when it's happening. This means to me I am sloshing around too much fluid and pushing air on the gears instead of fluid.... Or is this a computer problem? I don't see any metal shavings in the bubbles that would cause them.

Any help would be appreciated. It's a 1998 4T65E.
Sounds like you need a PC soleniod. A bad PC solenoid will cause harsh shifts in city driving, launch shuddering, and harsh garage shifts. This is a very common problem. If a P0748 or P1811 is stored in the PCM, replace the PC soleniod and your problem will be solved. The problem needs to be pretty bad to set these codes though.
 

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Discussion Starter · #7 ·
Sure enough I had a P1811 stored. I found out by visiting a local shop with a Snap On code reader. For 20 bucks he set it up to read the special codes from my car, he told me regular ODBII doesn't tell you much. So I'm thinking I need a new PC solenoid. How hard is it to replace, where is it? Where can I buy one?
 

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magilson said:
Sure enough I had a P1811 stored. I found out by visiting a local shop with a Snap On code reader. For 20 bucks he set it up to read the special codes from my car, he told me regular ODBII doesn't tell you much. So I'm thinking I need a new PC solenoid. How hard is it to replace, where is it? Where can I buy one?
You can buy a PC solenoid at any GM dealer or at Intense-Racing.com. They are kind of a PITA to replace. They are located on the valve body of the trans, which means the side cover has to come off. It takes me about 2 hours to do at work but doing the job at home without a lift and pole jacks will be an all day project. If you take it and get it done at a shop they will charge you around 6 hours labor. :eek: So it might be worth it to do it at home its your call.
 

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Discussion Starter · #9 ·
If it only happens every once in a while could it possibly be a dirty valve body?
 

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magilson said:
If it only happens every once in a while could it possibly be a dirty valve body?
Yes that could cause odd shifts, but 95% of the time its a PC solenoid. I have never replaced a valve body for hard shifts. Its always been the PC solenoid.
 

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Discussion Starter · #11 ·
askx125 said:
Yes that could cause odd shifts, but 95% of the time its a PC solenoid. I have never replaced a valve body for hard shifts. Its always been the PC solenoid.
Well I wasn't planning on replacing the valvebody, just adding a little seafoam trans cleaner to it. A local tranny guy recommended adding some and running with it for a while so long as a trans flush was in the near future.
 

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Yeah it couldn't hurt it, but don't get your hopes up too much. It's most likely not going to solve the odd shifting. :(
 

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Discussion Starter · #13 ·
Well I ran the SeaFoam. There was clutch material everywhere. I spent like 30 minutes just cleaning it all out. After all the fluid went in and I leveled it off when up to temp I took it for a run. I reset all the saved values for the trans and let me tell you it runs like a car just off the assembly floor. I have been trying to get the trans warm by stop/go traffic and I can't get it to shift hard anymore. I used to only be able to drive about 10-15 minutes in the city before it started shifting nasty but after 45 minutes of just driving around the city and so on I can't get it to happen. (I understand it's cooler out now but it was still shifting rough the week before so....) Hopefully prolem solved but at least the chance of bad failure is much smaller now... Hopefully...

Also, does anyone have a good method for inserting a new filter, every time (twice) I have done it I never feel like I have it in all the way and it makes me nervous, any thoughts?
 

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Did the sea foam fix the problem?

Any other tranny issues?

naot76 :cool:
 

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Discussion Starter · #15 ·
naot76 said:
Did the sea foam fix the problem?

Any other tranny issues?

naot76 :cool:
Ever since I did the fluid change after running with SeaFoam for a day I haven't had any problems. I'm not sure I would call it a miracle product, I think it's obvious my PCS problem was due to material buildup and it just needed to be cleaned out. The fact that that solenoid has a real issue still exists. However, its cheap, changing trans fluid doesn't take that long, and it lets you clear up some possibilities makes it a first step I would recommend to anyone who is having an issue. Just remember, a dirty trans may not be the issue that's causing your problem so don't jump to conclusions about SeaFoam if it doesn't work for you. There are a few people I know who even leave about a quarter of the bottle in their trans fluid at all times and swear it makes the trans last longer and run smoother. But thats about as acurate a measure as when people claim gains using their "butt" dyno... :rolleyes:
 
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