How long does the transmission last?

I have been told that it lasts till about 100,000 miles and then needs rebuild.

Does it cause any problems using the shifter or sport mode all the time?

I was told that it can cause problems, which does not seem right if you it shifting with in the limits and not powering the car too much.

 

Which car? The XJ8 and XJR have different transmissions.

 

Sorry! Yes that would help I have a 1998 XJ8

 

The XJ8 has the ZF5HP24 transmission which can suffer from A drum failures due to pressure spikes caused by the pressure regulator valve. There is an updated PRV that can be fitted to prevent this issue (part no 1058-327-030).

This problem seems to show up in the 60 - 100K mile range.

 

You have a ZF 5HP24. There is a known issue with the high pressure valve body in the tranny; the body scores, the piston hangs, and a pressure pulse overstresses the input clutch basket.

For what it's worth, BMWs and Audi with the same box have the same issues, so it's not Jag-specific.

Installing a rebuilt and updated valve body may forestall or head off the issue; but at that point, installing a reman with updated parts is not that expensive considering.

Yes there is an issue; but it's not life threatening in and of itself. It can be dealt with (as many, including me, have done). Now, whether investing 2500-3000 in a tranny (for the overhauled unit, rip and replace labor) is worth it in a car that's only worth 4-5K is a decision only you can make, though.