Hello all,

I am looking at buying a 1996 Jag XJ6 with 129k miles. It's a bit of a project, but projects don't bother me. I daily drive a 1974 Alfa Romeo Berlina so I'm used to quirks and whatnot.

I had a chance to drive this one tonight, but only got it up to about 50 MPH on the freeway as there was rush hour traffic. But at that speed it seemed to still be in 3rd gear. Pulling the gear shift over to 3rd didn't affect it at all.

But I'm wondering if I just didn't reach the speed needed to drop it into 4th.

The car has a few check engine codes related to rear O2 sensors which is no big deal. But it also had a rumbling noise somewhere, which could be wheel bearings, or possibly a diff going bad? Again I hope to take it out again tomorrow and take it on a few on/off ramps to load up one side or the other to check for wheel bearings.

If it won't shift into 4th I will pass. Wheel bearings, o2 sensors, etc I don't mind. They all seem to have issues at this age, but people are still asking well over blue book for this. I can pick this one up for under $1k so I have room to make the necessary repairs to bring it back up to top shape.

Otherwise it ran well, started fine, the heating system worked, radio, all windows, door handles, lights, sunroof, wipers, etc. Body and paint in great shape, tires good, glass good, interior good except some wear on the driver bolter and sagging rear headliner.

I will report back tomorrow, but if anybody can chime in on when theirs shifts into 4th I'd appreciate it.

Thanks!
Ian

 

That electronic trans should be in 4th by then, unless you had the boot into it, which it sounds like you did not, traffic etc.

Stale trans fluid is my first best guess.

Low trans fluid next.

That ZF trans is strong, but fluid is its weak point, both low, and old.

 

If it's in sport mode you need to be going faster, and even in normal mine is just at the point of shifting at around 50. It doesn't take much throttle pressure to keep it in 3rd at that speed.

 

I thought of that as well last night, I will check again today. Thanks!

 

I am more familiar with BMWs but I know the ZF is tough based on those. I did check the fluid and it was red and full. I will get it going faster today and see how it goes.

 

My 1997 X300 will shift into fourth gear as early as 28 MPH if I feather the throttle with the selector switch in the "N" position. If I am more aggressive then 32 to 34 MPH. It locks the converter typically at 52 to 54 MPH. making 29.5 MPH per 1,000 RPMs.
A filter change and new fluid "should" rectify the situation.

 

The torque converter lock may be what I experience. Does that drop the revs lower than the shift to 4th? I definitely have a drop of a few hundred revs at about 50 mph if not pushing too hard and by sixty with moderate throttle (tpi under 30%).

 

YEP.

That is a distinctive drop in revs, and is at that 50-54MPH mark.

 

I just don't understand this converter lock thing. What actually happens at that point?

 

The convertor "locks up", mechanically in this case, and becomes like a conventional flywheel (manual trans item), thus reducing slippage, dropping revs, and using less fuel.

The 4HP22/24 unit can be a very HARSH lockup feel, usually due to stale fluid gunmming up the workings.

ZF here suggested to me that I use Full Synthetic Trans Fluid, and do my normal drop and fill a number of times to get the new fluid concentration levels up in the 90% area. They did NOT recommend a flush, which I do not believe in anyway.

This improved the whole transmissions operation after 5 drop and fills, and by the time I got to 8 the "lock up" was barely felt. Prior to this fluid upgrade, the "lock up" was almost a BANG.

Mine was the "poverty pack" with the mighty 3.2ltr engine and the 4HP22 mechanical transmission.

 

So the mechanical lock up is some sort of dog clutch that slips into place - I know that's a crude description but in effect that's the case?

Interesting what you say about the 'bang' effect and how to smooth it out. I tried changing the oil via 3 drop and fills and I'm not sure it got that much better and I'm not sure it was fully synth oil.

I only recently realised how complex these auto boxes are and I am full of admiration for the guys who design and build them.

 

I reckon that is an excellant description for it, crude maybe, but spot on.

There are lots of talk around where that convertor does NOT release when slowing, and the engine stalls. Worse case scenario, but it is out there.

Fresh fluid of any spec will eventually clean all the gunk out, just that Synthetic has a higher temp rating, and supposedly better detergent packages, which is the "long service life" part of the Synthetic oil promo.

 

Thank you.

Final question, mixing fully and partial synth is presumably OK?

Mike

 

The trans/car will LUV you, its a Jaguar, we must have FAITH.