Well I have been having issues with my 4.4 v8 5hp24 gearbox when pulling away I would get a large shunt in the back and when warmed up it would hang in gears longer than it should so I done a fluid change it was slightly better but still not right , so was going to get another box anyway so I thought nothing to lose take the valve block off and inspect it only to find the casting completely cracked off ? Apparently a common problem . Will another valve block solve my issue ? It has also had a lack of engine braking in 1st gear

Click image to enlarge

Nothing to lose, you pretty much found the reason why you were having issues

Have a go

RRPhil on here is God when it comes to this gearbox in particular. He will be along shortly I am sure. sadly he has retired from the Gearbox business but is still the font of all knowledge.

Thanks for the help Well I fitted a secondhand valve block filled with fresh fluid and it drove perfect for about an hour until I got in some slow moving traffic then it was changing up past 2nd no faults were coming up but it seemed like it was in cool down mode stopped let it cool down then it drove fine all the way home . So now I must have a problem with either the gearbox cooler, thermostat or radiator which is it most likely to be ? Is it possible to jet wash the radiator through it will it be completely clogged ?

The gearbox cooler is fed by the lower part of the radiator IIRC and gets sludged up. A New radiator is your best bet I reckon.

You could disconnect the Radiator hoses & try flushing the radiator. See what comes out.

Worth having a go before replacing the rad, You've got nothing to lose.

It's gonna be your rad, there pretty cheap and easy to replace I got mine off the bay you have done the hard work.
Iv got a new spare in my garage not sure how I ended up with 2 but not sure how far you are from me

Just checking, but was your replacement valve body assembly definitely a ‘350’ model (i.e. 1058 127 350)?



Phil

Hi Phil

I am not 100% sure it came from a 4.0 Jaguar XK8 , I plan on dropping the sump for another fluid change so I can check then .I have the 2 pics of the replacement valve block from the ebay listing I will put on here

https://www.ebay.co.uk/itm/Aluminum-Radiat...635-2958-0

Better than the original which is plastic, I will proberly fit 1 of these at some point