AT Slipping. Why?

[Enemy]

What is making my AT slip?

I picked this car up in July. By August, The AT went out. I got a used AT to replace.

So, we have a totally different trans going in. But, we used the same torque converter.

The replacement AT works, but since then has gradually been getting worse weekly. It slips a little more and a little more every week.

The fluid isnt leaking and hasnt dropped since then. It doesn't make grinding noises or shift rough. It just slips.

Why?

Could it be the TC? Why?

Please help.

-Enemy

[kandyflip445]

Muahahahha. Of course it doesn't make grinding noises. It uses a bunch of clutches to direct power through planetary gears. I would try changing the fluid first. Take it to a lube place and have them do a transmission flush. It'll cost more because they have to use 20-30 bottles of ATF to flush the system. This will clean out the valve body and the servos. If there is too much or too little ATF you could cause the fluid to be aerated and this could cause slipping. Also check the torque converter for leaks. If the torque converter is leaking or if it has any damage you need to replace it.

Does it do it in only certain gears or does it do it in all gears? Does the engine run smoothly? Are there any other driveablity problems?

[Enemy]

"Does the engine run smoothly?"
Then engine runs very smoothly. The only problem with the engine is a minor engine oil leak (more like drip) and Im pretty certain that it's around the oil pan. But idle's great, everything functions properly.

My only beef with this car is the AT.


"Does it do it in only certain gears or does it do it in all gears?"
Well it's most common trying to get into second or third. I don't think I've noticed it on 4th or 5th, but thats mainly because if it doesn't get into 3rd, I'd have stopped the car by then and restarted it. Sometimes turning the car off, then on, can fix the issue. But not entirely because the trans will still shift a little weird... a lil weak.

When we had the TC out, it looked to be in good shape and didnt appear to leak. If the TC is leaking, it would be obvious while it was out correct? Or does it have to be tested in another way?

"Are there any other driveablity problems?"
Not really, No.

[Enemy]

I'd love to simply fix this AT if possible... but it just looks like I'm gonna invest in either swapping in a 5-speed or trading this car for a Coupe.

[kandyflip445]

Try the tranny flush. It can work wonders. How do you check the fluid in the car?

1. Check for fluid leakage.
-Clean any areas suspected of leaking.
-Start engine, apply foot brake, place selector lever in 'D' wait a few minutes
-Stop engine
- Check for fresh leakage

2. Fluid level should be checked using "HOT" range on dipstick at fluid temperatures of 50-80*C (122- 176*F) after vehicle has been driven approximately 5 minutes in urban areas after engine is warmed up.

-Park vehicle on level surface and set parking brake
-Start engine and then move the selector lever through EACH GEAR RANGE, ending in "P"
-Check fluid level with engine idling
-Remove dipstick and wipe it clean with lint-free paper
-Reinsert dipstick into charging pipe as far as it will go
-Remove dipstick and note reading. If level is at low side of either range, add fluid to the charging pipe.

DO NOT OVER FILL.

Fluid Condition

-Dark or Black with burned odor
Wear of frictional material (clutches in the AT)

-Milky Pink
Water contamination: Road water entering through filler tube or breather

-Varnished fluid, light to dark brown and tacky
Oxidation: Over or Under filling/Overheating

^^^From the FSM.

Also when you check get a little bit on your fingers and rub it around and smell it. It shouldn't smell burnt and you shouldn't feel any grit. If you smell either you have some wear going on. I'm still leaning toward fluid levels. Check that out then I'll post some more up if it checks out. Fluid levels can make the AT do all kinds of weird stuff.

[Enemy]

My AT doesn't suffer from leakage. There's never any spots under the car where I park. There isn't any indication of leaking when I look at the AT from underneath the car or anywhere near it for that matter. Fluid level on dipstick hasn't dropped since we installed the second AT. Yes, I always check like the FSM says.

But, I do think it may be overfilled. I'm gonna go ahead and try to drain some of it. See what happens.

I'll let you know later.

Thanks!

[Jonnie Fraz]

By using the same TC you may have transfered the problem over to the new tranny. You say the original tranny went out, if there was any debris in the TC you could have transfered it to your new trans. Anybody that rebuilds automatic trannies will tell you that cleanliness is key. Any little particle can cause the valves or servos to stick. Try the flush, hope it works, it will cost you less than tearing into it right off the bat.
Hope this helped.

[Enemy]

Ok... we drained some of the excess fluid out. So far so good. Shifting great. Got an engine oil change while I was at it and obviously the engine is running smoother even thought it has nothing to do with the transmission. Anyway, shifting is more precise and pretty smooth.

I'll let you know how it keeps up within the next week or two. You have to remember it wasnt slipping daily. It just had like bad days. So let me see how it goes, if no slippage in a week or so, then most likely excess fluid was the issue.

I'll still get a flush soon.

Thanks for the help.

[kandyflip445]

Actually the way the engine runs does effect an AT transmission. :p

[projectRDM]

You made one serious mistake when swapping the transmission that no one ever thinks about.

When the auto unit blows a servo or diaphragm or the filter comes apart, trash is introduced into the fluid and cycled through the transmission. This is what begins to tear more stuff apart. The fluid also cycles through the radiator, filling the bottom cooler with trash and debris that doesn't always come out under normal pressure.
As soon as you put a new one in and start it up, you begin pumping that same trash right back into the new transmission. I just replaced one last week and added a remote cooler, after blowing out the radiator's tank there was still a good deal of silt like material coming out of it. You'll never get all that out. An aftermarket cooler is like $30.

[kandyflip445]

A transmission flush actually gets a good deal of that out. Like I said they use (depending on the machine and how dirty your fluid is) up to 30 qts. Most of the metal will be on the magnet in the pan. The rest is clutch material, which is pretty much a paper-like substance bonded to the metal to make clutches.

[Enemy]

I did not know that. That's awesome info.

I plan on getting the tranny flushed at AAMCO in a week or two. Car's been shifting great since we drained the excess fluid.