When the car gets into high gear and needs to downshift going up a hill, approximately around 45mph, the car will jerk. If I let off the gas, then reapply, it will go into a lower gear. If I apply more gas aggressively, it will go into a lower gear.

Is this the transmission, or do you think it could be bad gas, or something with the fuel line, like the fuel pump. The car only has 44k on it. I recently had the fuel filter changed about 3k miles ago.

This car is new to me by 6 months and I'm unsure of prior maintence. I wanted to flush and fill the tranny, but it's sealed for life.

Any advice on next steps>
Thanks

 

Hello I am also a relitively new Jag owner, but have been a tech for over 20 yrs and recently installed a new 4.0 engine in my S. The real kicker is the fact that they sealed our tranny's but it can be serviced. I used a trans service machine and hooked it into the cooler lines at the radiator, using hoses and clamps to make the connections,and ran the fluid till it was clear. I then used a funnel on the return line to pour in an 8 oz. bottle of red Lubeguard. It's sold at Orielly auto parts. It's worth a try to service first, and the Lubeguard is wonderful stuff! I have had Honda's brought into the shop taking off in 2nd gear and shifting harshly, and after service and Lubeguard straighten right up and shift normally. My 2c's Curt

 

Instead of breaking the seal on the transmission, I decided to try fuel injector cleaner. I've also kept buying gas from the same BP station; premium only. The car is running much better, so I think it is a fuel line problem. When I first bought the car, I did have the fuel filter changed with an Advance auto filter and my problems started shortly after. Any thoughts, on getting a jag fuel filter and see if that fixes my problem completely.

Thanks!