drive take up delay

[l7jnd]

Hi, hoping someone here can give me some info. I have a 1987 mini mayfair auto. 51000 miles. Worked fine last year no problems at all. Garaged over winter. Yesterday drove out of garage fine, reversed back in fine. This morning drove to mot, passed mot! On the way back from mot the following problem..

in neutral then select 1st, 2nd, 3rd or drive, or reverse, revs decrease as tho gear engaged, let off brake and it wont creep like it used to, in fact in wont go forwards until you get to around 1400rpm then it shoots off and drives fine til you stop again. Its like the brakes are stuck on but the car freewheels fine and just passed mot. 

I have changed the oil, same as what was in it last year, old oil only done 600 miles, 20/50.
checked oil level, fine
checked governer rod adjustment, fine
idle speed is approx 900/1000 rpm
checked gear selector cable and it selects all gears fine, it just wont creep.
I have the ap manaual for the auto trans and have done the stall test in 1st and reverse and it all seems within spec

It feels as tho something is sticking somewhere, as once you get it going forward the slow down it creeps fine.

need to sort this as it wont hold on hills in forward gear as there is no creep.

seems odd to have suddenly gone like this.

could it be the low pressure valve letting the oil drain from the torque converter.

open to any suggestions,

thanks. Jim.

[kalkat]

Maybe jut sulkin after bein stuck in te dark?


Emma (wit a faulty keyboard)

[notamini]

I'm not too sure what the problem is but you need to change your oil before the car goes to hibernate. The auto box does not like mineral oils sitting in it for a long time. Apparently, they can become acidic. This leads to damage to the 'O' rings and rubber seals. My guess is that you have some goo to flush out. Maybe with time or with an oil change you can fix it.

[l7jnd]

Thanks for the reply. It has fresh oil, so maybe I will drive it for a bit and change the oil again and see what happens.
thanks,
Jim.

[69hcode]

Did you ever figure this out? My car does the same thing when put in gear. Seems fine if I don't put it in neutral at a stop. Takes of normal but very slow takeoff.

[wimfournier]

Lately I opened up my AP box to have a look inside to get understanding of how it works.
To answer your question, take in mind that the labyrinth where the sequentional gear changes are made consists of narrow canals with plunjers in it resting against springs that opens and closes the respect oilways. This labyrint is standing straight up. So over winter the oil in the canals tries to go down, saeking the lowest point. Where oil goes comes air.
So one day in the early springtime you wake up your Mini and try to get on the road.
Helas, the gearbox is not awake already.
It has to get rid of the air that is captured in the labyrinth. That will take some time. Only hot engine oil can speed up the process a little.
So, be gentle to your car, Take your time. And keep believing.

The recommended oil is 10W40, did'nd you know?

[Stu]

I'd agree with Wimfournier. The valve block can easilly become contaminated with sludge and can affect gear changes and performance from cold. +1 for 10/50 oil on boxes after 1979.

Also agree with warm up time, I'm sure I've read this is recommended in the auto owners manual booklet

[69hcode]

Just changed my oil. I was running 20w50.


I did a stall test before I changed it. Right at 1000rpm's. After the change about 1200 rpm's. I think it's due to tuning and high altitude. We are at 5,000+ feet up here.


Seems to take off a little better from a stop. Seems to shift a little smoother as well.

[Stu]

I assume you've swapped to 10/40? It might be a good idea to run the car for say 500 miles then change the oil again.

[69hcode]

I plan on it

[mra-minis]

Dec 19, 2015 22:57:16 GMT 69hcode said:

Just changed my oil. I was running 20w50.


I did a stall test before I changed it. Right at 1000rpm's. After the change about 1200 rpm's. I think it's due to tuning and high altitude. We are at 5,000+ feet up here.


Seems to take off a little better from a stop. Seems to shift a little smoother as well.

Have you got yourself a localised drivers handbook for your cars model and year ? check what oil it lists, as some countries maybe hotter/colder and the oil type changes accordingly ... however in most cases it is 10W40 for 79 onwards, also can you pressure test your transmission ? as it would appear you are losing pressure from somewhere or the flow is not being controlled by the various valves. It is doubtful to be a valve body fault as your symptoms are not control related, however never say never ....

I would start with a transmission pressure check, also do you have an engine oil pressure gauge ? what is it reading ? does it jump as you rev it up and as it finds a gear ?

look for changes and report back so we can all benefit :-)