Hello fellow members...

Haven't been active much lately, partially due to busy-ness, partially as the cat has generally been running okay, or at least without issues I need to pick the collective wisdom to help solve. (Wasn't much point in posting about the fuel pump failing yet again as I was halfway across the country on a road trip, and the vast expense of getting the car trailered back home....)
But lately, I've noticed hesitation on setting off quite often. The revs will increase, the car barely respond, then suddenly, as if the gears have finally meshed, it'll take off. And sometimes while running, I'll feel a lack of power, but then it comes on. And at the lights, from time to time there's a sudden, brief surge of power and the car almost tries to move forwards. I can also detect, from the lowered noise or vibrations coming to a halt, when the car is going to be unhappy moving off again. It seems to go a bit quieter than normal.
Am I right in thinking this is a slipping clutch plate? I took her into my usual garage this morning, and while they haven't had time to diagnose the issue, if it is a clutch plate needing repair, how serious is that?

Some background, based on a post last year from Charles in HK: I did have her sitting for a good month, unused, and there was a fairly large spread of transmission oil on the ground after, but the levels (checked when hot) seemed fine to me. Could it just be needing new transmission fluid and/or a filter? It's certainly been at least five years, from memory, that the fluid was replaced, and probably longer. Then she needed new coils, and had to sit for a few more weeks as I was overseas. I've been driving a moderate amount in the last week or so, but mostly in Drive rather than changing up and down the gears - she did seem happier in second, for example.

I just don't want the garage to go ahead and drop the tranny, send it off to their tranny specialist, him probably doing more work than needed and me end up paying big bucks when it's not a big-bucks issue.
That said, if it is the clutch plate needing replacing, how difficult would that be? Just so I can talk about the issue with the mechanic with a bit of knowledge, offer suggestions, etc. if needed.

Thanks in advance, everyone, as usual....

 

Basics first, as always.

Is the fluid at or slightly above the FULL mark when HOT and running at Idle in P?
When was the fluid last changed?
The trans filter has a plastic suction tube that has an O/ring at the pump Inlet end. They crack, the pump sucks air, its easier than fluid, and drive quality of the trans goes down the drain, basically as you describe.
The Nylon Gov Gear strips, stuff happens, BUT, that causes all sorts of shifting issues.

Of course it could be just plain worn out, but that is raare on the TH400, they are TOUGH, but stale fluid is their killer, oops.

 

Thanks as always, Grant.
1. I checked the fluid when the car engine was hot, but off. This appears to be the wrong time. But it was definitely above the F mark on the "Hot" side of the dipstick. Assuming that wasn't smears....
2. It has been several years, but not more than about five or six. How long does fluid last? Hmmm....
3. Interesting. Cracked O-ring? I'll let the mechanic know. I assume he'll check things like filters, but just in case....
4. Other than the sluggish take-offs and weird flat bits while driving (when the car appears to be on half power--but I assume one bank isn't just randomly cutting out. The cap and rotor were replaced six years ago, the spark plugs and leads are even newer, and the coils were replaced last month), I don't sense any chaos. Just slowness.
Very helpful info, thanks.

 

Yep, engine MUST be running.
Pull the stick, wipe, insert, pull straight out and read the level.

Life, hahaha, about 5 years or 80k kms is the average, but we could argue that all damn day, and waste some serious drinking time. ALL mine get drop and refill every 2 years, no matter the kms traveled, even the pretend Jag.

The filter is a Dacron medium unit, and does clog over time. That o/ring is often missed, UNLESS they know, or have been caught out previously.

 

Sounds like a classic case of low fluid level. You can top it up yourself with a liter of fluid and a funnel.

As Grant says, car must be running, in park and on level ground. The fluid should be hot too, which usually means after 20-30km of driving. From memory there is also a cold mark on the dipstick, you can use that if you want. I think it's about 3/8-1/2" below the hot full mark.

To top up, you pour fluid down the dipstick tube with the stick removed, a small amount (maybe 250ml) at a time and then recheck the fluid level, always with the engine running.

 

Thanks, Grant and Jagboi. Always good advice.
Engine running to check, and replace more often. Got it. Yes, been a bit distracted with other projects lately and haven't been able to focus fully on the Jag. Not good, I know.
So I assume that the engine off (even if warm) would let oil return to the reservoir, giving a falsely high reading?
The O-ring, I assume, is this black ring in the top right of the photo. From the fact that a gasket that looks like it fits the fluid reservoir is included in kits, I assume that the filter is inside, no?

 

Yes, without the engine running the fluid partially drains back from the torque converter giving a false high reading.

The filter material is the yellow stuff you see inside the metal, but the whole metal assembly is called the filter. There is usually a small tube that goes between the transmission body and the filter and fits into the rubber gasket you see.

There is also a rubber gasket at the top of those tube where it goes into the transmission and sometimes when the filter is changed that upper gasket isn't removed. Then the new filter comes with one and it's put on the tube and you have two gaskets in a space designed for one. That will cause a lack of drive as the pump is sucking air past the mushed gaskets instead of fluid. However, you mentioned you did have a leak ( not uncommon when standing a while and the fluid drains out of the converter), so I think it's a simple case of low fluid.

 

Here ya go.

#8 in the parts schematics is the little sucker that reeks so much havoc.
I cannot attach that schematics for some reason, maybe the Jag Gods are upset, HA.

My dealings with it are:
Stays in the pump inlet (as said) and then gets doubled up oops.
Falls out and runs away, and not being seen, is not replaced.
Comes out on the end of the plastic tube, and is cracked. PREFERRED scenario, coz you see it and do something about it.

Down here some trans filter kits include that o/ring, some do not.

The "grommet" in the top of the filter is part of the filter unit and not removable under normal situations.

I agree, low fluid is the likely cause. pour a litr in, and see what happens.

 

Thanks very much Jagboi and Grant.
Do you mean Part No. EAC5544 in this schematic?
Anyway, I'll call today and make sure they're testing the basics like fluid levels before going right ahead to taking the entire transmission off.
I should definitely have come to the forum first, but I had managed to convince myself (thanks to mis-reading the fluid level) that there was plenty of transmission in there.

 

Some Say Some Day,

No, it's the seal at the top of the tube on the filter. part 8 here:

https://parts.jaguarlandroverclassic.../brand/jaguar/

Confusingly it's not shown on the facelift parts diagram, but it's the same box and filter.

Cheers

Paul

 

Ah, okay. Got it, thanks.
Found some good diagrams of the transmission here too:
https://www.jag.co.jp/jrc/images/th400.pdf
Page 10 has a diagram of the filter, etc.

 

The internal components are the same as the General Motors transmission, so there are a ton of videos on Youtube showing rebuilds of the TH400. The filter/fluid change is the same as a Chevy with the same transmission.

 

Pity I don't live in a place where Chevys are common.
Oh well. I should phone the garage and make sure they're not immediately taking the transmission out to send to a transmission specialist....

 

Just phoned the garage, and spoke to the mechanic.
You were all right. Lack of transmission oil. And they tightened up the sponge seal a bit.
Lesson learned: always check with the the masters at Jaguar Forums before panicking and getting convinced something critical has failed....
Thanks, everyone, as always.

 

Happy to help! Glad it was so simple ( and cheap).

 

SWEET.

I say it again:
These are SIMPLE cars, only made complicated by over thinking, and under drinking.

Enjoy.