P38 Paul Posted June 22, 2023 Share Posted June 22, 2023 Hi everyone, I have a new problem with the car juddering at low speed, it happens when I am close to full lock in both forward & reverse at low speed (5mph). in most cases it try's to do small wheel spins as if the diffs are not working & the diffs locked, it still drives fine in a straight line (normal driving). Does anybody what's going on with it or experienced anything like this before? Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted June 22, 2023 Share Posted June 22, 2023 If a P38, sounds like your central viscous coupling has seized. On loose surfaces it is fairly normal (and OK) for there to be scrubbing, but on tarmac/concrete it should allow a degree of slip and not chirp tyres. Testing on a bench/under the truck: You can also test with one front wheel jacked up, put a 2ft wheel brace on on e of the wheel nuts and stand on it, it should rotate smoothly, maybe 10s per quarter turn or so? 2 Quote Link to comment Share on other sites More sharing options...
P38 Paul Posted June 22, 2023 Author Share Posted June 22, 2023 20 minutes ago, Bowie69 said: If a P38, sounds like your central viscous coupling has seized. On loose surfaces it is fairly normal (and OK) for there to be scrubbing, but on tarmac/concrete it should allow a degree of slip and not chirp tyres. Testing on a bench/under the truck: You can also test with one front wheel jacked up, put a 2ft wheel brace on on e of the wheel nuts and stand on it, it should rotate smoothly, maybe 10s per quarter turn or so? Hi Bowie69, thats great info thankyou, do you think that the car is still ok to drive everyday without doing the repair or will it cause more damage in the long run? Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted June 22, 2023 Share Posted June 22, 2023 Long term it will does stress thing, but for a short while it will be fine, avoid tight turns and lots of power and very likely fine. 1 Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted June 22, 2023 Share Posted June 22, 2023 Or take the front prop off and drive with rear wheel drive only. It's not good for the viscous coupling - but that's shot anyway. Obviously not viable if you need four wheel drive. 1 Quote Link to comment Share on other sites More sharing options...
P38 Paul Posted June 22, 2023 Author Share Posted June 22, 2023 Is this a difficult job to do on the floor with no ramp? Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted June 22, 2023 Share Posted June 22, 2023 8 bolts! Easy enough access. Quote Link to comment Share on other sites More sharing options...
P38 Paul Posted June 22, 2023 Author Share Posted June 22, 2023 3 minutes ago, Bowie69 said: 8 bolts! Easy enough access. Thanks Bowie69, you're a star. Quote Link to comment Share on other sites More sharing options...
P38 Paul Posted June 22, 2023 Author Share Posted June 22, 2023 27 minutes ago, geoffbeaumont said: Or take the front prop off and drive with rear wheel drive only. It's not good for the viscous coupling - but that's shot anyway. Obviously not viable if you need four wheel drive. Thankyou for your input geoffbeaumont for your valuable input. Quote Link to comment Share on other sites More sharing options...
Snagger Posted June 23, 2023 Share Posted June 23, 2023 It’s almost certainly a seized viscous unit as they said above. Ashcroft Transmissions sell refurbished VCs if you can’t find a good used one. I have never done the job myself, so can’t give any advice beyond expect the parts to be heavy as well as slippery, and get a set of wheel ramps and chocks to give yourself a bit of working space - they aren’t that expensive and are useful for many other jobs too. Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted June 23, 2023 Share Posted June 23, 2023 10 hours ago, Snagger said: I have never done the job myself, so can’t give any advice beyond expect the parts to be heavy as well as slippery, and get a set of wheel ramps and chocks to give yourself a bit of working space - they aren’t that expensive and are useful for many other jobs too. If the car still has air suspension, that's not really needed - just raise it to it's highest level. But, as with any work under a car with air suspension, put axle stands under the chassis so it can't drop on you. Do not rely on just the inhibitor switch or an open door! A proper transmission jack is well worth it for safely dropping the transfer box and even more so for getting it back in - they're not that expensive, but you may well be able to borrow one (shame I'm not still in Birmingham - you could have used mine). Can't comment on rebuilding the transfer box, I've only swapped the whole box over (on a Classic, never had to do this on the P38). Quote Link to comment Share on other sites More sharing options...
P38 Paul Posted June 24, 2023 Author Share Posted June 24, 2023 11 hours ago, geoffbeaumont said: If the car still has air suspension, that's not really needed - just raise it to it's highest level. But, as with any work under a car with air suspension, put axle stands under the chassis so it can't drop on you. Do not rely on just the inhibitor switch or an open door! A proper transmission jack is well worth it for safely dropping the transfer box and even more so for getting it back in - they're not that expensive, but you may well be able to borrow one (shame I'm not still in Birmingham - you could have used mine). Can't comment on rebuilding the transfer box, I've only swapped the whole box over (on a Classic, never had to do this on the P38). Hi Geoff, I was hoping that I can get the viscous off without having to take the transfer box out, I had a look underneath yesterday and recon with the front prop out of the way I should be able to undo the viscous casing and swap it over. Quote Link to comment Share on other sites More sharing options...
P38 Paul Posted June 24, 2023 Author Share Posted June 24, 2023 21 hours ago, Snagger said: It’s almost certainly a seized viscous unit as they said above. Ashcroft Transmissions sell refurbished VCs if you can’t find a good used one. I have never done the job myself, so can’t give any advice beyond expect the parts to be heavy as well as slippery, and get a set of wheel ramps and chocks to give yourself a bit of working space - they aren’t that expensive and are useful for many other jobs too. Hi Snagger, I have a decent set of ramps & chocks so I recon I'm going to have a go at this job myself. 1 Quote Link to comment Share on other sites More sharing options...
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