CraigM Posted April 21, 2017 Share Posted April 21, 2017 Help please, guys. My son has got a 91 LR 3.9v8 auto which has developed a bad shudder. It only happens on take-off. Feels like a clutch slipping. If I pull away really gently, it doesn't do it, but if I pull off normally it shudders like hell. I'm afraid I'm a bit lost. Anyone got any ideas? Quote Link to comment Share on other sites More sharing options...
steve b Posted April 21, 2017 Share Posted April 21, 2017 It could be the transmission brake not releasing fully ? does shudder or clunk when coming to a stop ? Also does it then change up/down through 2/3/4 cleanly? What does the oil on the autobox dipstick smell like ? cheers Steve b Quote Link to comment Share on other sites More sharing options...
CraigM Posted April 21, 2017 Author Share Posted April 21, 2017 Thanks Steve b. Firstly, I should have said it was an RRC. Secondly, I drove it home from work tonight carefully and it's pretty bad. Finally It lost "D" - just revved like it had slipped out of gear, but it ran in 3, 2 and 1. So definitely transmission, but not sure what... Quote Link to comment Share on other sites More sharing options...
Paul Woodward Posted April 21, 2017 Share Posted April 21, 2017 Could be the chain jumping if it's a Borg Warner transfer box. Quote Link to comment Share on other sites More sharing options...
steve b Posted April 21, 2017 Share Posted April 21, 2017 It could be the chain jumping , or maybe the viscous diff locking , but first check the auto box oil level , warmed up and in park , ticking over ,having been shuttled between D & R . The symptoms suggest oil issues , level and/or quality or possibly a blocked pickup filter Steve b Quote Link to comment Share on other sites More sharing options...
simonr Posted April 22, 2017 Share Posted April 22, 2017 Most auto box problems are down to the oil. First try topping up. If that doesn't help, change the filter (take the sump off to find the filter) and the oil. My guess at the cause of the shuddering is the band brakes (the equivalent of clutches) slipping. This usually happens (initially) due to low hydraulic pressure due to low oil or blocked filter. You need to fix it quickly as the slipping heats the oil up to the point of burning (going black / dark brown) and damaging the friction surfaces permanently. Si Quote Link to comment Share on other sites More sharing options...
Snagger Posted April 22, 2017 Share Posted April 22, 2017 Possibly a torque converter issue, especially if it does it in higher gears. Slipping clutch packs would cause the same problem, but I find it unlikely that they'd all fail at the same time (I believe there are three packs in a ZF 4 speed with reverse). Replacing the torque converter is cheaper than rebuilding the box, so would be a good start point if replacing the fluid and filter (filters are rarely replaced by most garages) doesn't sort it. There are some very good videos on youtube explaining how TCs and autos work, so you'd see how worn clutch packs would cause this. They are the Achilles heel of the auto transmission, but also (with the TC) the reason why you can't shock and overload an auto... Quote Link to comment Share on other sites More sharing options...
Range Rover Blues Posted May 1, 2017 Share Posted May 1, 2017 On it's own, a vibration could be the flex plate on the torque converter has cracked. It's not uncommon and I think Ashcroft's now make a spring steel one as an upgrade. As a warning, if an old autobox suddenly get some TLC in the form of new oil, the detergent in the new oil lifts ingrained dirt and carries it to the governor, which acts like a centrifuge. It's again not uncommon for this to result in a gearbox failure, such as sticking in second for example, as the governor sticks. So if the box is suffering neglect I'd suggest a couple of changes of oil over the coming weeks, drop the oil without staring the engine too as the muck will settle in the sump. Quote Link to comment Share on other sites More sharing options...
Snagger Posted May 2, 2017 Share Posted May 2, 2017 It's the sprag clutch. Common enough that Ashcroft redesigned them for their own units and gives the exact symptoms you describe - slipping in D but fine in 1, 2 and 3. Quote Link to comment Share on other sites More sharing options...
paintman Posted May 5, 2017 Share Posted May 5, 2017 (edited) From Ashcroft's website: Q. I have a 4sp ZF, when I select "D" the vehicle won't move, when I select "1" the vehicle moves off. I can then select "D" and continue to drive normally. If I stop I have to start in first again. Why? A. A sprag clutch has "inverted" and will need replacing. No further damage will occur if you continue to drive but you will need to select "1" every time to start moving. A rebuild is required to correct this. http://www.ashcroft-transmissions.co.uk/frequently-asked-questions/4hp22-faq-s.html Edited May 5, 2017 by paintman Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.