Do any of you know what makes the tranny shift at certain MPH points. Mine shifts fine until it gets into 4th but seems to shift into overdrive too late and sometimes not at all. Presently it does not shift into overdrive until 52-53 MPH is reached. On some vehicles that shift point is determined by shift cable. I do not know if this one is like that or is electronically controlled from the transmission control module.
My 1996 Cougar with a 3.8 liter V6 shifts into overdrive at 42 MPH as does my '86 Toyota 2.5 liter 4 banger. An earlier shift point would save wear on the engine and fuel in city driving. Any info will be appreciated.
Cheers, RagJag

 

4th gear *is* overdrive on your trasnsmission.

I wonder if you torque converter lock-up isn't working? That can alsmost feel like an additional 'gear'.




If I'm correct that your TCC (Torque Converter Clutch) isn't locking up then you likely have an electrical/sensor issue. The TCM looks at road speed and throttle position, from the appropriate sensors, and commands the TCC to lock-up based on those readings. Actually 50-55 mph doesn't actually sound wrong for TCC lockup. Some manufacturers specify that range to avoid excessive locking/unlocking at lower speeds....which would be annoying to some.

Cheers
DD

 

Ragjag,

It sounds as if its working perfectly ok. The zhp24 box is set to lock up at about 52mph unless you're still accelerating hard. That lockup will feel like a change up with revs dropping to about 1700 rpm.

It's set like this to try and hold the highest ratio of speed to revs just before it gets to 56mph. This is because one of the mandatory UK fuel consumption figures is quoted at 56mph.

So, nothing to worry about.

Paul

 

Just for the hell of it I took mine out for a ride. Sure enough I could make it bounce back and forth depending on what side of 52mph I was at.

Mine is the same as yours 96 XJS 4.0L 2+2 Convertible

Happy Motoring!!!!

Softball60 Paul

96 XJS 4.0L 2+2 Convertible
1957 XK140 Drophead Coupe
1989 Merc 560SL

 

Thanks for the replies. Locking up at 52 mph seems late to me but if that is correct I will live with it. I will have to take it to my transmission expert and see if the sensor is malfunctioning because it doesn't always lock up when it should even with me feathering the fuel pedal trying to get it to do so.Thanks all for the help.
Cheers, RagJag