Acceleration Problem

[Bongolia]

Worth checking the points raised by the others on here re vac pipes etc before a/box specialist, it would cost nothing.
If all looks OK make friends with gearbox guy.

[teenmal]

Thanks guys.

It's a diesel. The revs increase on the rev counter but the vehicle speed increases very slowly, the engine still feels like it pulls but not very fast and only to a point. The fault appeared suddenly. i thought I heard something slip/disconnect under the drivers side.
The weather was average. Dry but not particularly hot or cold.

Thanks for the gear ratios. The revs were definitely higher over 30 mph or so.

To save yourself a lot of expense and hassle check the RPM to MPH and let us know the exact figures that you or your mechanic are getting .bellow is what it should be higher RPM to MPH would indicate gearbox/clutch slipping.you should are getting

Gear Ratios
(mph/2000rpm) for each
gear.
1st – 11.2MPH
2nd – 20.4MPH
3rd – 32.0MPH
4th – 50.3MPH

[cmm303]

Thanks guys.

It's a diesel. The revs increase on the rev counter but the vehicle speed increases very slowly, the engine still feels like it pulls but not very fast and only to a point. The fault appeared suddenly. i thought I heard something slip/disconnect under the drivers side.
The weather was average. Dry but not particularly hot or cold.

Thanks for the gear ratios. The revs were definitely higher over 30 mph or so.

To save yourself a lot of expense and hassle check the RPM to MPH and let us know the exact figures that you or your mechanic are getting .bellow is what it should be higher RPM to MPH would indicate gearbox/clutch slipping.you should are getting

Gear Ratios
(mph/2000rpm) for each
gear.
1st – 11.2MPH
2nd – 20.4MPH
3rd – 32.0MPH
4th – 50.3MPH

teenmal, can you help me understand this "test".

I understand how this would work with a manual clutch. The torque converter in an automatic relies on slip to transmit power and the only time this slip is eliminated is when the torque converter locks in 4th gear. On the level my Bongo starts off with the engine idling, But on a hill it needs more engine revs to start off, so there must be more slip, I thought needed to transmit more force to the driven side of the torque converter and thus the wheels. So I don't understand how speed and revs can be exactly related, except when cruising in 4th. I must be missing something!!

[teenmal]

cmm303 , sorry but I cant get my head round this "Slip" that you are talking about, the last thing you want with any type of gear box whether auto or manual is Slip.
Why not take your vehicle for a wee run and let us know what figures you get, it would be very helpful.

Thanks.

[g8dhe]

Perhaps this article might help explain the operation, especially the Torque Converter rather than the fluid coupling spoken about above ? https://en.wikipedia.org/wiki/Automatic ... _operation

[cmm303]

cmm303 , sorry but I cant get my head round this "Slip" that you are talking about, the last thing you want with any type of gear box whether auto or manual is Slip.
Why not take your vehicle for a wee run and let us know what figures you get, it would be very helpful.

Thanks.

I'll give it a go on the level. I do know that when accelerating fairly gently, my road speed can continue to increase with very little change in revs, especially so in higher gears. Also when it locks the Torque Converter there is a distinct drop in revs. Maybe my Bongo has a transmission fault

Agreed the gearbox does not slip but slip is inherent in a torque converter. That is why the engine does not stall when in gear with the vehicle stationary. It is also what makes automatics less efficient than manuals and why the torque converter is locked at cruising speeds to eliminate that inefficiency when gear changes aren't required.

Perhaps this article might help explain the operation, especially the Torque Converter rather than the fluid coupling spoken about above ? https://en.wikipedia.org/wiki/Automatic ... _operation

Useful stuff, helps to clarify terminology. I presume the Bongo has a Torque Converter.

I take from this that
a) there is slip and it varies.
b) the Torque Converter transmits torque more effectively than a simple fluid coupling when slip is large.

The test is respected by those far more experienced than me so I wonder if it is valid because at a steady state 2,000 rpm the slip should be less than x% and therefore within the tolerance of the result expected.
Lets see ....

[hugsjugs]

I'm away for a few days now so wont be able to take the van out but when I get back I'll take it out again.

When I say I felt something slip I mean it sounded like something came apart/disconnected but it was a faint sound. I was travelling at 70mph on a motorway that sound could have been something else. I mention it because I thought I heard it moments before the acceleration issue.

[hugsjugs]

Hi. Just want to say thanks to everyone well replied. This problem is now fixed!

After going to a gearbox specialist to a garage only to be sent to another gear box specialist (no charge thankfully) we finally went to our regular garage who spent proper time looking.
The fault was a turbo clip. Cost £2.95. More for labour to find the fault but it was relatively inexpensive fix in the end.
Thanks

[Bob]

Phew, glad its sorted.

[mikeonb4c]

Great news

[Northern Bongolow]

you say you heard a noise, this maybe the turbo pipe that has come adrift or has got a hole in it, remove and check the air filter, this is under yer bum and if something has been sucked into the filter this could give your symptoms, a noise on your side and loss of performance.