jsp
Rover Rookie
Posts: 7
|
Post by jsp on Jul 4, 2015 13:23:06 GMT
Good afternoon all, Im looking for some help diagnosing a strange fault with my p5b gearbox. ive lost the selection of first gear D1 whilst all other gear positions work as they should. The car drives fine in D2 and will kick down into first without problems and I can set off in first in the lock position L however when D1 is selected there is just a whirring noise and no drive, seems strange that first is broken but not? any help would be greatly appreciated. many thanks, Joe
|
|
|
|
Post by norvin on Jul 4, 2015 15:56:18 GMT
Good afternoon all, Im looking for some help diagnosing a strange fault with my p5b gearbox. ive lost the selection of first gear D1 whilst all other gear positions work as they should. The car drives fine in D2 and will kick down into first without problems and I can set off in first in the lock position L however when D1 is selected there is just a whirring noise and no drive, seems strange that first is broken but not? any help would be greatly appreciated. many thanks, Joe harvey is who you want so lets hope he logs on. |
|
|
|
Post by harvey on Jul 4, 2015 18:39:57 GMT
Good afternoon all, Im looking for some help diagnosing a strange fault with my p5b gearbox. ive lost the selection of first gear D1 whilst all other gear positions work as they should. The car drives fine in D2 and will kick down into first without problems and I can set off in first in the lock position L however when D1 is selected there is just a whirring noise and no drive, seems strange that first is broken but not? any help would be greatly appreciated. many thanks, Joe There's something wrong in your description of what's happening. D2 locks out FIRST gear, and so drive starts in SECOND, so AFAIK in "D2" you won't have kickdown into FIRST, you'll only have kickdown and downshifts from TOP to SECOND. Pulling away in "L" will mean you pull away in FIRST and stay there. "D1" is fully auto, so if it won't pull away when that's selected then the one-way-clutch has failed. |
|
jsp
Rover Rookie
Posts: 7
|
Post by jsp on Jul 5, 2015 1:34:25 GMT
Thankyou for the quick replys, my mistake it kicked down from 3rd to second. Is the car still safe to drive with this fault? I was hoping to get a bit more use over summer before tackling a gearbox rebuild and the car seems to drive fine using d2. Any steep hills could I set off locked in first then shift into d2 at speed? Joe
|
|
|
|
Post by enigmas on Jul 5, 2015 3:46:44 GMT
Here's a picture of the sprag/one way clutch. It's up to you to decide whether anything has come loose on the component that could possibly damage the rest of the valve train. The component locks one way and runs free in the other direction...that's why there's no engine braking in this gear in Drive unless Lockup is selected. Unfortunately replacing it means a major strip down of the gearbox.   Here's a link to an updated sprag www.makcotransmissionparts.com/A119654.html |
|
|
|
Post by harvey on Jul 5, 2015 14:12:02 GMT
Is the car still safe to drive with this fault? I was hoping to get a bit more use over summer before tackling a gearbox rebuild and the car seems to drive fine using d2. The one way clutch supports the front of the gearset on the centre support, so if the clutch breaks up the gearset won't be supported there. Add to that the possibilty of broken bits being loose in the box and you have the chance of damaging more than has been already. I wouldn't say it's dangerous beyond the fact that it could grind to a halt at some point. Any steep hills could I set off locked in first then shift into d2 at speed? Joe If you start in "L" and get up sufficient speed you can just knock the lever forward into "D1" and it should pick up SECOND. |
|
jsp
Rover Rookie
Posts: 7
|
Post by jsp on Jul 5, 2015 14:30:22 GMT
Sounds expensive, would I be best trying to obtain a second hand box to rebuild? Or am I best with the devil I know?
|
|
|
|
Post by harvey on Jul 5, 2015 14:42:02 GMT
Sounds expensive, would I be best trying to obtain a second hand box to rebuild? Or am I best with the devil I know? I'd be inclined to dismantle the box you've got first and see what you find inside. Buying a secondhand box means buying a totally unknown quantity, regardless of what the seller might tell you. Whatever hard parts your box might need I should have good used items that I could sell you, and all the gaskets, seals and bands are still available new. |
|
jsp
Rover Rookie
Posts: 7
|
Post by jsp on Jul 5, 2015 16:38:10 GMT
I'm trying to figure out the best way to go about the job with keeping the car on the road over summer as much as possible, another thought was buy a second hand box and send it to j r wadhams, any experience with their rebuild service? I would imagine it would cost several hundred pounds to rebuild my own properly? I'm quite capable with the spanners but never touched an auto box before so I'm trying to weigh up time vs money although I can't really afford to throw £1000 at Wadhams at the moment. And the most upsetting part is Id promised the car to my brother for his wedding in about 8 weeks time. Many thanks again for all your help so far, it's great that there is so much help and advice on here. Joe
|
|
|
|
Post by petervdvelde on Jul 5, 2015 21:09:18 GMT
i don't think Wadhams overhaul these boxes themselves so they will send it to a specialist and make their mark up.
In your case i would ask Harvey to overhaul the box as looking at all the answers he has given (BW35 related) on this forum and the P6 forum, he is a true specialist and he can when needed supply second hand bits at i assume reasonable prices.
Peter
|
|
jsp
Rover Rookie
Posts: 7
|
Post by jsp on Jul 6, 2015 11:51:37 GMT
right,ive decided to remove the box and dismantle it myself and attempt a rebuild, I found a fantastic article on this forum which im sure most have seen and i think with time patience and care there is no reason i cant succeed with a rebuild. could anyone recommend a parts supplier for a rebuild kit? ive googled but not found much, there is one on ebay but its overseas. thanks, joe
|
|
|
|
Post by guidedog on Jul 6, 2015 11:59:45 GMT
Wakey Wakey JSP look at previous threads Harvey can supply & you will know you have the right parts
|
|
jsp
Rover Rookie
Posts: 7
|
Post by jsp on Jul 6, 2015 12:07:11 GMT
thanks for the nudge guidedog i will do just that, ill crack on and get this box out (which doesn't look easy)make a list of knackered parts and ask Harvey very nicely to sell me some spares. id misread the post thinking if i asked Harvey to rebuild it id need to supply the parts with the box. joe
|
|
|
|
Post by harvey on Jul 6, 2015 14:09:33 GMT
|
|
|
|
Post by harvey on Jul 6, 2015 16:10:35 GMT
If it makes any difference to your course of action, thinking about it again, the front of the gearset is actually supported on a white metal bearing and so the one way clutch isn't taking most of the load, but if it's broken the bits are going to be working their way into that bearing. I had one a while back though, and because of a breakdown in communication he ended up using it for ages with the one way clutch failed, without it causing any further problems.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jul 20, 2015 9:30:06 GMT
Rather than start a new thread...............
I know little about auto boxes but why should a BW35 thump when the lever is mover to D or R from Park. No matter how slowly mine ticks over there is a thud and slight jolt and I'm told that this is considered normal,even though it seems like an design weakness and I'm further told it does no harm.
Is it the gearbox internals set in motion then stopping as the prop cant rotate,or the torque convertor suddenly stopping?. Elementary to those who understand these things I'm sure but not to me!.
|
|
|
|
Post by eightofthem (Andy) on Jul 20, 2015 12:33:55 GMT
Might be worthwhile looking at your throttle valve cable Kev, I am a bit reluctant to use the name kick down cable, ( it does far more than just kick down ) as this causes confusion on times with quotes like " I don't use my kickdown " so the throttle valve / KD cable may need adjustment, if it is too tight then this can cause the valve to be slightly open, thus allowing pressure to flow, and can cause the " thud " you describe.
Worn or corroded inner cables don't help either.
I had terrible trouble getting the idle correct on mine, it turned out to be the inner cable was corroded on the throttle cable ( pedal to carbs ) it looked good from the outside, but was rotten internally, changed it and have a nice smooth idle.
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Jul 20, 2015 12:57:32 GMT
The cable is free and the cam in the correct position at tick over which is 600 rpm. The 'thud' is only just noticeable I'm just curious as to what components inside the box are responsible for it.
|
|
|
|
Post by enigmas on Jul 20, 2015 13:03:26 GMT
Kev,it's quite logical if you think about it. If the engine's running, the front pump is active as is the torque convertor supplying oil to all the open circuits. Also, the faster the engine is idling the greater the torque output of the convertor. At fast idle when the engine is cold and with the hand brake applied selecting either drive or reverse engages the appropriate elements. The resulting energy needs somewhere to go. It's usually taken up within the free play of the drive train. (How much backlash does you differential currently have?) (For every force applied, there is an equal and reactive or opposing force) Before putting your car in gear on a cold morning, warm it up, return the engine to a slow even idle, take the hand brake off, then place it in gear. This will produce the least clunk. Putting the car into reverse whilst at fast idle can snap the rear servo mounts off (near/at the 2 retaining bolts) Later BW51 autos (Aussie) incorporate a 3 bolt rear servo. The 3rd bolt is mounted to the side of the servo and cannot be fitted to earlier transmissions. Of the 3 torque convertor sizes available, the unit fitted to the MK3 will produce the least clunk for several reasons. It is the smallest, (having more 'inbuilt slip'), the working pressures are lower and the 3 litre engine idles at very low revolutions, producing less torque multiplication at low engine speed.  |
|
|
|
Post by norvin on Jul 20, 2015 14:35:59 GMT
Rather than start a new thread............... I know little about auto boxes but why should a BW35 thump when the lever is mover to D or R from Park. No matter how slowly mine ticks over there is a thud and slight jolt and I'm told that this is considered normal,even though it seems like an design weakness and I'm further told it does no harm. Is it the gearbox internals set in motion then stopping as the prop cant rotate,or the torque convertor suddenly stopping?. Elementary to those who understand these things I'm sure but not to me!. My box is the same and mine has had a complete rebuild. I have checked the K/D cable which is ok I have spent time adjusting the mixture with my colour tune and getting the balance correct on the carburettors making sure the idle is at 600 RPM. this has all helped to make the gear selection smoother. What I find helps is to hold the foot brake on with the handbrake and pause in neutral before selecting D or R. |
|
