G/box: 850 Auto: Reverse Problem - Not yet changed ATF - but considering

[Andy_H]

Hi all - I hope you all can help

I have a M Reg Auto 850 T5. Over the last few weeks the use of reverse is very limited. It simply revs and has very little actual drive.

1. If the engine is completely cold reverse is relatively okay
2. When the engine is cold, it does occasionally get stuck in 1st or 2nd, but shifting it to lower gear manually forces it to right itself.

A. I have checked the Diagnostic fault codes - nothing is showing as problem
B. All the dealers I have spoken to have reccomended against doing an ATF flush.
C. I have researched extensively these problems and can see that an ATF flush or PNP switch are possible candidates.


If I cant solve this problem I am going to have to scrap her - and that makes me sad because I really enjoy the car!


Have it booked in to be reviewed by a Volvo specialist Monday - but should i bite the bullet and get the flush done?

What you reccomend?

Thanks

Andy

[dooby]

Hi,

hard to make a recommendation but some more info might help - what is the current condition of the fluid? Colour, smell, etc.

I'm not sure I fully understand the rationale why flushing auto fluid might be bad. I guess with engine oil and a flushing agent (to thin out the oil) I can see that maybe it loosens a clump of sludge and blocks an oilway - in addition to potentially causing a borderline seal to fail as the sludge was helping it hold together.

But in my experience, even after 100k miles auto box oil isn't that bad. You don't have combusion by-products coming into contact with auto box oil, the system is more sealed than the engine oil setup. You also don't use a flushing/thinning agent, and you just use the auto box's pump itself to pump the old fluid out so I'm not certain I understand where the risk comes from.

If it was me I might be tempted. I probably wouldn't use Volvo stuff in your case as it's very expensive and if the box does fail it'd have been wasted. But do go for a reasonable quality brand which matches the required specification.

HTH, Pete

[Andy_H]

Thanks so much for your reply - I see you have responded to similar posts on this before so I am grateful.

Fluid is a darkish brown colour, certainly not the redish colour of new ATF. There is also a definate burning smell when reversing, but the dipstick smell reasonably okay. (fluid level is correct)
Car has done 160K, and never had fluid changed.


I think the rationale was that changing the fluid could make the situation worse, and make the problem more pronounced in forward gears.

I wouldnt go for the cheap stuff I see in Halfords but would look for Dexron III type stuff from GSF or Unipart rather than Volvo dealership. (quoted around 30 for 5 litres)

Thanks

Andy

[Lmason]

i would most likely say the pnp switch is the cheaper and easier, most likely cause. there is also a microswitch in the gearlever selector box which is also a common thing to go. there only about £3 if you goto the right places, ie try a washing machine shop,

[Andy_H]

Thanks for the post..

I soke on the telephone with an auto transmission specialist today who thought it unlikely to be the fluid or switch, but more likely the reverse clutch burned out (hence the dark color atf) He thought the flush would be waste of money.

Really confused as to what to do as so many different opinions.

I still thnking i will do the flush purely to eliminate that, but what does the PNP switch actually do? (Park Neutral Position?) How would this affect the Reverse and why woudl I get partial reverse when cold?

Thanks in advance

Andy

[liuleichan]

Originally Posted by Andy_H

Thanks for the post..

I soke on the telephone with an auto transmission specialist today who thought it unlikely to be the fluid or switch, but more likely the reverse clutch burned out (hence the dark color atf) He thought the flush would be waste of money.

Really confused as to what to do as so many different opinions.

I still thnking i will do the flush purely to eliminate that, but what does the PNP switch actually do? (Park Neutral Position?) How would this affect the Reverse and why woudl I get partial reverse when cold?

Thanks in advance

Andy

To be honest, from the symptoms, I'd be inclined to agree with the auto specialist. I don't think it's PNP related. And I think there's limited point to an ATF flush - that could go either way in your situation - extend the time until it properly stops working, or hasten it's demise. And I think it highly unlikely an ATF change will resolve the problem.

[Paul240480]

My bro' had a Mazda 323 auto many moons ago. Reverse conked completely he did an atf change & it solved the problem

Don't ask me why, it just worked.

As for being against a flush, I can't really follow that. I always thought with an auto box fluid changes were as important as engine oil changes for longevity?

My old 480T auto had all atf changes noted in the file. I did the last one in my myself. Sold with 146k miles & the box was a sweet as a nut & it's still going strongly today.

Good luck

[liuleichan]

Originally Posted by Paul240480

My bro' had a Mazda 323 auto many moons ago. Reverse conked completely he did an atf change & it solved the problem

Don't ask me why, it just worked.

Well it's the slippage, the mention of temperature and ATF discolouration that's making me think the clutch on reverse is going.

If the clutch is going, it's never going to get better. Now an ATF change may slightly prolong the situation, and add some life, or speed up a total failure. But it won't fix it.

Reverse slipping is quite a different situation from a gear sometimes not working - that may be for conditions unrelated to that particular gear's clutch.

[Andy_H]

Thanks for your posts people - its greatly appreciated.

I still driving it and just being creative when it comes to needing to park. I thinking I going to drive it for as long as possible.

I notice if I use the gear selector and hold it slightly towards D when reversing it does improve the situation a little and I can usually get it to reverse enough for most purposes.

Love the T5 - and reckon this wont be my last!!!

Thanks

Andy

[Andy_H]

Update on this:

I finally got round to replacing the PNP switch and also drained and replaced ATF. (did not do a full flush)

However car is permanently stuck in 3rd it seems (Winter mode) - and if I go to L - after 3 mins or so I get the flashing arrow and code 322 showing on diagnostic. Reset codes, and still stuck in 3rd - its like it wont find 1st or 2nd.

Could the PNP be faulty? Incorrectly aligned or gearbox fried?

Thanks