Won't Stay In Overdrive

azchevy99 · October 5, 2008

I have a '99 Silverado 1500, 4.8L, 4L60e tranny. Yesterday, I dropped my tranny oil pan and replaced the filter. The tranny took a little over 4 qts to refill, which is pretty normal. Now though, the transmission will not stay in overdrive. It will shift to overdrive, but then shift back right away. Would overfilling the tranny fluid cause this, or maybe I somehow caused the shift cable to become out of alignment (you have to remove the cable somewhat to get to a tranny pan bolt)? Thanks!

azchevy99 · October 6, 2008

I can't say that I've seen a trans very slightly overfull causing an issue, it's possible though. Are you sure it is overfull because with pan removal on a 4L60E I usually see refill amounts in the area of 5 qts. Did you check after the road test? I usually get them nice and hot then go for a road test reaching overdrive a couple of times then recheck. I suspect you are actually low not overfull.

I made sure it was at normal operating temp before I checked... drove it around quite a bit and got it to overdrive a few times. So it's definitely slightly more full than it needs to be, but yes it would be weird if that were the problem. I pumped about half a quart out of the filler tube (the drain plug is a PITA). Now it's barely over the full line and still won't stay in overdrive. Is there anything I could've messed up taking the pan off?

minibike132 · October 6, 2008

I don't do a whole lot of trans work so your getting best educated guess advice here. I have my areas and this isn't one of them but no one else is jumping in here so I'll let you have it.

Was it tight getting the pan out? I have seen trans problems caused by hitting the solenoids and related wiring when pulling the pan. I wouldn't think that would cause it to come out of overdrive once in but I could be wrong. If you replaced the filter and caused dammage to the seal that the filter goes in you will have air entering the pump and that will be a problem too. That also goes for any dammage to the filter itself.

azchevy99 · October 6, 2008

So I took my truck to a tranny service station. They couldn't figure out the problem and want to take the tranny out to find out what's wrong. They thought it was due to a pressure issue, and didn't think it was a solenoid because there were no error codes. Does this sound like it could be the cause?

azchevy99 · October 6, 2008

Yeah it was pretty tight because of the shift cable bracket. Hopefully I didn't hit a solenoid or something. I have the deep pan, so the filter (the all plastic one) has the seal built in to the neck. Maybe I'll have to take the pan back off and make sure I didn't break something.

redvett · October 5, 2008

There hasn't been a shift (TVS) cable since 1992 on the LD #1500 my b3et you have a "O" ring loose/leaking on the filter or a low fluid level.

azchevy99 · October 5, 2008

The shift cable is right next to the tranny on the drivers side. Not sure why you think there hasn't been one since '92. If anything, the fluid level is a little high. Not much, but maybe a quarter inch above the full line while hot.

redvett · October 5, 2008

He may be thinking of the TVS cable because the shift cable should be OK if he just R&R it. You can tell if its not in the proper gears by shifting between P-R-N &D if they aren't where they should be its adjusted wrong. No adjustment is required for a filter change.

azchevy99 · October 5, 2008

So if the fluid level is too high, would it cause the tranny to not stay in overdrive?

azchevy99 · October 6, 2008

I picked up my truck from the tranny shop. Didn't want to pay $450 just to have them take the tranny off and look at it. Overdrive will stay engaged as long as I have my foot on the gas, but as soon as I let off the gas, it downshifts. Does that help diagnose the prob? Also, it slips just a little when I'm at a stop and take off.

minibike132 · October 7, 2008

Yeah it was pretty tight because of the shift cable bracket. Hopefully I didn't hit a solenoid or something. I have the deep pan, so the filter (the all plastic one) has the seal built in to the neck. Maybe I'll have to take the pan back off and make sure I didn't break something.

So I took my truck to a tranny service station. They couldn't figure out the problem and want to take the tranny out to find out what's wrong. They thought it was due to a pressure issue, and didn't think it was a solenoid because there were no error codes. Does this sound like it could be the cause?

Well I don't know where to go with you on this one. I'll start with this, none of the filters have the seals built into the neck. You should have removed the filter from the trans and the seal would have stayed in the hole the filter went into. You should have removed that seal and installed the new seal included with the new filter then installed the new filter. If you did not remove the old seal and installed the new filter with a seal on it then you have one to many seals. That would be a big problem and it would be possible to get it all togeather that way with the deep pan.

Second you would not necessarily set a code right away if you did dammage a solenoid. It might sound far fetched but believe me the trans isn't always being monitored the way you think it should be.

Lastly it is not unheard of that transmission problems can occour after a transmission service that was done properly. Transmission fluid has detergents in it. Especially on an old or heavily worked trans new fluid can cause a problem. Often on an older trans the only thing keeping the clutches working is the old film on them. Change out four or five quarts of fluid and the new stuff washes off the clutches and you have problems. Take it to another place if you don't trust that place, find someone you trust.

75HOW30 · October 7, 2008

Those can be a real bear to get the pan out of . I would think you would want to really check the shift cable asjustment. This can be checked by placing into R-N-D . What your feeling for is no drag in neutral ( do not want any "force" pushing shifter to either side when in neutral), and should feel centered from side to side - a little wiggle test will help. Did you bend the shift cable bracket? Did you break the shift cable retainers at the bracket? Is the "paper clip" retainer reinstalled to make sure the cable is completely into the bracket?

Seems like a code/check engine light should have shown up by now for a broken shift solenoid - but cant rule this out.

hope this helps

minibike132 · October 6, 2008

I can't say that I've seen a trans very slightly overfull causing an issue, it's possible though. Are you sure it is overfull because with pan removal on a 4L60E I usually see refill amounts in the area of 5 qts. Did you check after the road test? I usually get them nice and hot then go for a road test reaching overdrive a couple of times then recheck. I suspect you are actually low not overfull.