Auto gearbox poor performance
 

A friend of mine who wants to buy a R75 recently came across a low-mileage, apparently well cared-for, 2.5 V6 automatic for sale locally to him. At the weekend, I went along with him to look at it. First impressions were good in that the car was presented well and the engine revved sweetly. However, when we both drove the car, we were struck by how poor the performance was when the auto 'box was in 'Normal' mode. The engine just didn't have any get-up-and-go, especially when pulling away, feeling more like a 1-litre than a 2.5. In contrast, with 'Sport' mode selected, the car regained normal acceleration from standstill and pulled well under kickdown and at high revs.

Can anyone in the know offer their opinion please on what this (presumably) gearbox issue might be and how much it could cost to put right?

Would it be better to walk away from a car like this? Or buy the car, having negotiated an appropriate discount to cover the cost of a repair?

The gearbox issue aside, it would otherwise appear to be a solid, well-maintained car. Thanks for your help.

I havent driven a petrol variant of these cars, so cannot comment on any comparison to the diesel. My diesel is an auto, and can be as urgent or as relaxed as I choose. But they are adaptable or learning boxes, in that they learn the driver's driving style. I have reset it by disconnecting the battery (not for this purpose, and you can do it by removing the gearbox's fuse), and you do notice a difference in gear changes and reactions.

It is hard to put into words, but it is 'different' for a while. when I found out about this, I did once try it, and drove gently/conservatively for a while after. Fuel economy increased a little when I did this. and it seemed to short shift compared to how I was used to. After about 3 weeks, I returned to my normal driving style, (I would describe as yobbish grandad lol - hard away up to speed limit, if I wasnt going to stop or slow, and then cruise at speed limits). Once back to 'normal' the fuel economy dropped to 'normal' and changes were more efficient for progress.

In sport mode, the same principles apply, however, whilst it does hold the gears longer, it does NOT allow you accelerate quickly from a start, it maintains the gear ratio for longer, thereby keeping it within the torque range better. The gear ratios do not change.

So perhaps there is nothing actually wrong with the box. If the seller was agreeable, resetting the box may rule out an issue.

Remember also, these are not racing/quick cars, so it may also just be different to what you are used to? (I am not sure how different the gear ratios are between models, but this too, could explain it).

VIS motors are known issues, but I didnt think they affect lower revs, only becoming noticeable above 3000 rpm (or something like that, maybe someone could confirm this).

If there was a serious issue on the gearbox, it would show 'EP' in the display. You could also ask the seller when the fluid was last changed. I am not sure if it would be a reason, but I guess 'worn' fluid could cause the clutches to slip, and then be slow to take up the power. :shrug:

Whilst the 2.5 is not known to be lively at the bottom end at the best of times have the Vis motors checked ;). If they have failed, depending what position they have failed in, will/can effect bottom end performance and or economy. A failed balance in an activated position does make it sluggish, but then again don't expect lightning speed.

Hi Craig,

There won't be anything wrong with the gearbox. Automatic transmissions are very sensitive to engine tune. There are three things that are likely to be causing the poor performance of this car:

1. Faulty VIS balance actuator and/or stuck flap valve (as said by Stocktake in the last post).
2. Faulty VIS power actuator and/or flap valves in incorrect position.
3. Blocked breather filters in the camshaft covers.

I've had all three with my 2.5 litre KV6 engine and they're easily and cheaply fixed if your friend is DIY-minded.

When you next see the potential purchase, with the engine cold and running press the windscreen demist button to check that the air conditioning compressor engages and that the radiator fan runs continuously.

Also, using a powerful torch, look into the 'V' of the engine for signs of leaking antifreeze solution.

There is no need for your friend to be worried about the gearbox.

Simon

As above. My V6 was owned by an elderly gent who I guess, rarely went above the 3 thou revs to bring in the power vis. I am also very steady but occasionally will open her up to clear her lungs! It wasn't until I changed both the VIS motors that I could appreciate the difference. I also freed off the balance VIS flap as it was quite sticky in operation. The difference was chalk and cheese. The 3200 rev upwards power was so much better. Mine is also auto and surprises most folks with its split personality!;) I hardly ever use the sport mode but then I am approaching 70 (years not MPH!).:D

Thanks, all of you, for your helpful advice on this topic. It never ceases to amaze me just how much knowledge members of this club possess and how willingly, and quickly, they share it :}

From all of your comments, then, the car in question would definitely appear to be a serious 'potential buy' :D

Simon, you mention that the likely causes of the problem are 'easily and cheaply fixed'. Do you have a rough idea of how much these VIS actuators cost and (very) roughly how long it would take an MGR-trained mechanic to fit them? I'm afraid that neither I nor the potential buyer of the car are very competent on the technical side of things and always have work carried out professionally on our cars.

If I can estimate an approximate cost of repair, my friend could maybe make the case to the seller for a modest reduction in the asking price.

Contact Dave (Stocktake) Craig. He specialises in the repair, restoration and modification of the VIS system. Removal and refitting alone would not be expensive at any garage.

Simon

VIS motors:-
https://www.dmgrs.co.uk/products/vis...e62e9480&_ss=r
or there are upgraded versions available. (from stocktake on here ?)
Standard ones take about twenty minutes or less if you've done them before. Basically remove electrical plug and screws. Check operation of manifold components. If all is OK, swap gasket if you didn't get a new one. Replace.;) If doing it for the first time, you will need to know what to check on the manifold and how to fix it if it needs that.:shrug:Also the orientation of the VIS to manifold internal connections.

You have a rubber mat under the speeder?
The speeder cable is not properly adjusted?

The V6 is dreadfully lazy, unless you squash the pedal flat against the floor!

That is just how it is.:D

As for the auto gearbox, a neglected Jatco box can really affect the performance of the car. It is critical that the correct fluid be used and that it is at the proper level.
Even checking the level means raising the entire car and removing a plug on the bottom of the gearbox to check, which can only be done by pouring fluid in the filler on top of the box till it runs out of the plug. And, this all has to be done at the proper temperature. :duh:
All that taken into account an oil change car make a huge difference in performance. (Partial change actually as the fluid in the torque converter will not drain so it takes 3 or 4 "changes" to renew all of the fluid.)
You may want to ask your friend to at least have the level checked as it may make the car more saleable.