Help!! slipping gears / clutch on automatic??

This site contains affiliate links for which LandyZone may be compensated if you make a purchase.
B

Brutus76

New Member
Posts
14
Location
Chiswick, London
Hi, I just bought a 2001 P38 automatic diesel that seems to have a serious clutch/gear/transmission issue..Im naive and the seller is a b&stard unfortunately.. I have no clue when it comes to these things so I wanted to ask some advice if i may:

The car makes fairly loud sounds whenever starting, but perhaps just the diesel, but whenever i push the gas pedal the car does not "engage", as if the gears are not catching at all and just slipping. If I drive, it takes ages to get it up to speed for the auto-box to switch to 2nd and 3rd gears, and im frankly not sure its a good idea to drive at all..could i burn the whole box?? Any ideas what this could be?i took it to the local garage, but the guys just said the control-box must be changed, seemingly without even diagnosing anything etc. Any ideas for what may be wrong is greatly appreciated (before i go to other mechanics/garages etc). Thanks!!
 
It won't be the control box as they put it. The diesel is no ball of fire and there is normally a lot of slip in the torque convertor. You should see 4 changes by the drop in revs on the rev counter, on a light throttle they will all happen in sequence by about 40 mph, a 5th change which is torque convertor lock should occur around 50/55mph.
check the sport button and the light next to it.
If the car suffers from lack of acceleration, could be a lot of things.
 
Is there any warnings up on the dash? Any electrical faults and the gearbox will try setting off in third and it will be the only forward gear available
 
dogsbody said:
Have you checked the fluid level in the box? It just seems a logical place to start.
Click to expand...

Agreed, however a box faulting through low fluid is living on borrowed time.

There seems to be a lot of mention on here of sticking valve blocks. I've had literaly thousands of autoboxes apart over the years and I can count on one hand the number of times I've seen failures caused by sticking valves, and every one of those has been down to burring or scoring to the pistons caused by particles of metal from another failed part of the box.
The friction modifiers in ATF break down over time. Changing the fluids restores this meaning the clutch packs reach kiss point with lower line pressure which tends to ramp quite sharply. This is why it makes your box feel smoother. Most transmission failures are down to the clutch pack piston seals or annular ring seals that send oil to the clutch pack pistons wearing out and allowing fluid to leak past them, or the clutch plates plain and simple wearing out. As your clutch pack wears the piston has to travel further than originally intended causing a slow shift. A lot of modern electronic boxes compensate for wear by monitoring engagement speeds and adjusting line pressure to compensate. On the ZF 5hp24 in the l322 this reaches a point where the line pressure is so high it cracks the A clutch drum. The other main issue is the clutch plates simply wear out just like the clutch in a manual gearbox car. Other problems are overheating causing the plates to glaze or water ingress from faulty coolers simply steaming the friction material off the plates. An autobox clutch plate will destroy itself in seconds if it slips.
Lucas autobox treatment contains further friction modifiers as well as a seal conditioner which helps worn seals. Other than that each individual make/model of transmission has it's own weaknesses and faults. The 4hp24 suffers from broken sprag clutches for example.
 
Wiganerdan said:
Agreed, however a box faulting through low fluid is living on borrowed time.

There seems to be a lot of mention on here of sticking valve blocks. I've had literaly thousands of autoboxes apart over the years and I can count on one hand the number of times I've seen failures caused by sticking valves, and every one of those has been down to burring or scoring to the pistons caused by particles of metal from another failed part of the box.
The friction modifiers in ATF break down over time. Changing the fluids restores this meaning the clutch packs reach kiss point with lower line pressure which tends to ramp quite sharply. This is why it makes your box feel smoother. Most transmission failures are down to the clutch pack piston seals or annular ring seals that send oil to the clutch pack pistons wearing out and allowing fluid to leak past them, or the clutch plates plain and simple wearing out. As your clutch pack wears the piston has to travel further than originally intended causing a slow shift. A lot of modern electronic boxes compensate for wear by monitoring engagement speeds and adjusting line pressure to compensate. On the ZF 5hp24 in the l322 this reaches a point where the line pressure is so high it cracks the A clutch drum. The other main issue is the clutch plates simply wear out just like the clutch in a manual gearbox car. Other problems are overheating causing the plates to glaze or water ingress from faulty coolers simply steaming the friction material off the plates. An autobox clutch plate will destroy itself in seconds if it slips.
Lucas autobox treatment contains further friction modifiers as well as a seal conditioner which helps worn seals. Other than that each individual make/model of transmission has it's own weaknesses and faults. The 4hp24 suffers from broken sprag clutches for example.
Click to expand...

I know that.
 
Wiganerdan said:
Is there any warnings up on the dash? Any electrical faults and the gearbox will try setting off in third and it will be the only forward gear available
Click to expand...

Hi, thanks for replying. No, there are no warning lights at all. The car does not set off in 3rd, in fact it barely catches 1st and barely moves even if revs at 2-3000.. After 1- 2 minutes (perhaps whenever engine a little warmer) it does catch a gear or two, but still does not move at more than 15mph if up a small hill no matter how hard i push the gas pedal.
 
Thanks for help guys; I will check this, sport button and valve box, oil etc today..hopefully I find something that can easily be changed, and learn something about cars in the process!
 
Brutus76 said:
Hi, thanks for replying. No, there are no warning lights at all. The car does not set off in 3rd, in fact it barely catches 1st and barely moves even if revs at 2-3000.. After 1- 2 minutes (perhaps whenever engine a little warmer) it does catch a gear or two, but still does not move at more than 15mph if up a small hill no matter how hard i push the gas pedal.
Click to expand...

In all honesty I think you are going to be putting a gearbox in it. If it's slipping that much it's dead. I would suspect the fluid is going to be dark brown/black and with an awful burnt smell.
 
You must log in or register to reply here.

Similar threads

T
L322 Vogue reversing problem. Feels like brakes are on !
Replies
8
Views
517
nevillen
nevillen
MrMatt83
L322 3.0 td6 gearbox problems
Replies
12
Views
513
pwood999
pwood999
C
L322 td6 auto 2005 No Drive when hot
Replies
11
Views
413
backinblack
backinblack
S
L322 1st Time RR Owner
Replies
13
Views
331
stubaldock
S
feyniriel
Gearbox fault P38?
Replies
3
Views
243
Grrrrrr
Grrrrrr
Back
Top