Land Rover Disco 1 - ZF4HP22 auto box clunk. When I am cruising along in top gear, slowing down using the brakes, there is a loud embarrassing clunk from the drive train as it drops down to 3rd gear.
I don't get the clunk in any other situation. If the rate of deceleration is slow, by cruising slowly up to a set of lights, the noise is much softer and not noticeable, but if I apply the brakes to slow down in a normal manner, that's when the loud clunk occurs. I changed the auto oil and filter only about 5000km ago. The gear changes are a little sharp also, as I accelerate hard.
There does not seem to be any radical backlash wear in drive shafts, wheel drive nuts, diffs, etc that I know of.
I note that if I select 3rd gear for driving around town, I never get the problem. Its only when I am in Drive and slowing down. Is this a common problem?
I am assuming it’s a gearbox problem? would a gearbox service likely help?
Disco 1 is now officially older than the hills, and they were never renowned for excellence in build quality. (Very good off-road, however, with plenty of great all-terrain tech.)
If you Google 'Land Rover Disco 1 clunk' you get almost 200,000 results, so yeah - common problem. Or, problems.
The question is: is this clunk symptomatic of a problem you need to fix? Will it get worse and lead to a more expensive mechanical failure and you stranded at the roadside? I would need strange mental powers to decide, over the e-mail. (And if I had those I wouldn't bother answering your question because I would be too busy sorting out next week's winning Lotto numbers.)
You need to take your D1 to a Land Rover specialist. The noise could be from any number of sources: transmission, transfer case, driveshaft joints or prop shaft joints. It needs expert diagnosis.
Don't wait on this - it's always better to find out what's wrong before the vehicle spits expensive parts onto the roadside.
I wouldn't bother with a Land Rover dealer (rip off). I would approach these guys. They have a solid reputation and Land Rover is what they do.
Hope this helps.