So about a week or so ago I started to noticed the TC wouldn't lock up until after a couple of minutes of driving. I understand it may need time to for fluid to warm up, but I had never "noticed" it going into lockup before this. Two days ago I had the oil changed and they said the transmission fluid was "very low" and topped it off.

Last night It took a good 10-15 minutes of driving before it locked up. When it finally happened I was going 70mph+

This problem is new to me and have never experienced it on any other car. A search here didn't provide me with any info.

 

I am NOT aware of a temp sensor for that operation.

Being as yours is a 4ltr and has a 4HP24 "electronic trans", I would be getting a trans fluid service done, NOT just a "top off". It is a simple task to do.

My 3.2ltr did that when I first got the car, and 3 fluid changes in 18 montrhs and it is barely felt now when it activates at 82KPH. Mine is the 4HP22 "non electric" trans, it has a "kickdown cable", so is as simple as it comes.

I would doubt anything sinister, coz these transmissions are basically bullet proof, but CLEAN fluid is a MUST.

 

1. check the fluid level again yourself

2. make sure that the added fluid was of the correct type

 

Could it have an air lock if the fluid wasn't topped up properly?

 

I have a 1995 XJ6 and it does the same thing. It takes about five miles of driving and then it works fine. Have gotten used to it. Had the trans serviced couple of years ago. Don't know if it was doing it before that but it probably was. I think that is just the way it going to go.

 

Topping it off is NOT rocket science, pour the fluid thru the dipstick tube, preferably with the engine running, and check the fluid level on the dipstick.

I ALWAYS do this with the trans HOT, that is after 20kms driving, and on level ground.

There is NO WAY that bleeding is required, as there is no provision for that, other than the trans does it by simply doing what it does. The pump sucks the fluid out of the pan, and sends it thru the system to allow you to drive the car, thats about it.

A blocked filter can cause all sorts of havoc, as can stale fluid, that is why I suggested a fluid change as a first "attack" of this issue.

The daughters XJ40 (4HP22) also was "lazy" in this area when she first got it, and after several fluid changes and 1 filter change it settled down to be as I expected it should be (hardly felt).

It could be some other gremlin, but I seriously doubt it. The trans fluid is a much FORGOTTEN fluid, as is the power steer fluid. Then something goes "bang", then the fluid gets changed as part of the "fix", and quickly gets forgotten for a further 10+ years.

 

When I changed the fluid in my 95 about 10k back there was no problem with the filter and everything else looked good. The filter was changed of course. I'm pretty sure it has been slow locking up since then and maybe before. There fore I don't believe changing fluid will make any difference. I just think it is going to be a blit slow until the fluid warms up. It doesn't seem to be getting any worse and when it locks up you can hardly feel it. I know when it does by watching the tach.

EZDriver

 

Thanks for the replies. I guess I'll have the the fluid and filter changed. I've been checking on the fluid level and all seems good. I don't have any oil spots where I park, so not sure why it was low.

I wish they had told me it was low before topping it up, I would have had them do a drain and fill instead.

I'm starting to get a nice little list together of things that need addressed, but just can't find the time. Been going 12-14 hours a day (with a few 22 hour days in there), 6 days a week since February and still have 5 more weeks left.

 

Just an update, I finally got a chance to see the mechanic. He didn't know why it would be doing that, but he agreed with you guys that a fluid and filter change wouldn't hurt.

The fluid was actually over-filled by the oil change guys, which I noticed prior to bringing it in, and the mechanic asked me how they checked it which I hadn't thought about.

They checked it cold, engine off, and I had only driven it from my place less than half a mile away... Next time I have the oil changed, I'm going to tell them to just do the oil, I keep on all my fluids weekly.

As an aside, the mechanic recommended changing from a 10w30 oil to 20w50

 

Sounds like a plan to me.

I am still amazed at the people that should know better that still check auto trans fluid levels with the trans cold and engine off. the short drive you did would give odd readings, and now you know you can keep an eye on it yourself.

At the risk of starting another "oil war", I run 10W/40 in my AJ16 (and the V12) all year round. I tried the heavier and the engine was noticeably "less responsive", and when returned to the lighter oil, things returned to "normal". Modern oils are WAY different to what was available just 10 years ago, and I always use the latest spec (SL,SM,SN) in all my Jags no matter how old they are, and some are "senior".

 

This thread seems to have kind of wandered from the original query, TCC operation when cold.
On that subject, it is normal for the torque converter clutch to remain off until a certain temperature is reached. The reasoning is two fold; the obvious first one is hydraulic things just work better when warm, the second requires you to think like an engineer, and an automotive engineer at that. Since the early '80's just about everything an engineer does takes emissions into account, first and foremost. The big gun in reducing emissions is the catalytic converter. The converter can't work unless it is hot, very hot. Consequently, the sooner it is at temperature, the sooner emissions are reduced. That's why secondary air injection came about, to pour air into the rich exhaust required for cold running. It effectively makes the exhaust manifold a reactor to pre-heat the converter, heat it up fast. They use anything they can think of to heat the entire powertrain up fast as they can. [that's also why the coolant capacity of our V8's is so small, less coolant to heat up from cold] Back to the torque converter. The torque converter is a tremendous heat generator, that is when it is not locked up. You see where this is going. Engineers use it as another way to heat things up as fast as possible, all in the interest of reducing emissions.
In my experience the temp required to allow TCC engagement varies quite a bit. Some as low as 65-70 deg Celsius, and some as high as 80-82 degrees C. [that's coolant temp, by the way]

To look at this from another angle, this is so taken into account that today's cars actually can't survive without the TCC. If a TCC fails, an overdrive transmission quickly overheats due to the heat generated by the torque converter. A lot of trans failures could have been prevented if they had just noticed the TCC quit working. Some high engine temp issues are misdiagnosed because of a failed TCC that was overlooked.

Anyway, sorry to be so long winded, but I didn't know of a better way to get the point across. That's just another example how we techs have to be mindful of the whole picture, if we are going to be sure we get it right the first time. And maybe some folks will pay more attention to their own cars, and catch things early!

Cheers,

 

and I knew I didnt have to answer this question since you did Steve. Besides Jagular would just come in and point out some engineering point that I was WRONG about.
Youre totally correct and for all the right reasons

 

Thanks for taking the time to write this. I had my suspicion that it was heat related. Is there a temp sensor, or does the ecu send the signal telling it to lock up, or is it a mechanical function?

The strange thing, for me, is that I had never really felt it locking up before and now I feel it most of the time. Also, the first time it goes into lockup from cold it isn't at 50mph, which I was under the assumption was the speed at which it should lock up.

 

the tcm and ecu work together for speed, throttle angle, egine temp and load. But the trans has a temp sensor inside it also. its also related to helping the trans get to operating temp faster also since like Steve said, when you lockup the convertor it takes even longer to heat the trans fluid. This is another reason the trans coolers are inside raditaor to bring the trans fluid up to temp faster also. There is really a whole lot that goes on that no one except engineers and software programmers know what strategy is being done with 1/0's to operate todays technical systems. You have to think about reasons system may work together to produce a desired result. Kinda like the new 5.0 has 4 VVT units, 1 on each cam and we only had VVts on the intake before that retarded/advanced up to 48*, now they go to 62*. When you shut off the engine, 1 cam advances. 1 cam retards to reduce cam overlap for startup. and the new style VVTs now use a locking pin to lock out the VVT on shut down. Till started again and thats to stop VVT rattle on startup, which has been a complaint at times, but is not really broken, just the design of the part and a shortcoming......Now that issue is no longer 1. Another reason I posted in another thread that engineering REALLY got it right with the new 5.0

 

Thanks for the backup, Bill!