'98 V70R auto AWD - AWD prognosis?

[RollingThunder]

Hi all, I'm new to the AWD forum so please forgive the newbie questions - I have googled (for hours) but haven't really found any definitive answers! I've owned many Volvos and currently have a '98 V70R so I'm happy pulling the engine etc apart I've pretty much just bought a '98 V70R auto AWD to join the stable, so my thoughts are focussed on the AWD system which is new to me.

My queries/concerns are these -

1. Is the AWD system really so intolerant of mixing new/old tyres on the same axle? I've read on the web that you can't simply replace one tyre on an axle, you have to replace the pair?! Is that really true or just scaremongering? I assume front/rear differences are ok?

2. I understand that the main reason for the AWD failing (apart from potentially differing wheel diameters) is that a (transfer box?) seal fails allowing fluid to escape causing the bearings to overheat? If that is correct, is there an 'upgraded' seal that can be fitted as a preventative measure? How easy is it to replace the bearings? I've noticed that most people disconnect the propshaft and drive it as a FWD car, but I'll want to retain the AWD if it does start to have issues.

3. Is the '98 auto AWD model more or less prone to these issues? The one I have 99% bought only has 110k miles up so is comparatively low mileage (for a Volvo lol).

4. Presumably the rear diff will need regular maintenance too - is any particular oil recommended? I don't mean what is in the owners manual - what have owners found to be the best oil?

5. Finally (!!!) Do we have a resident AWD system guru that I can bug rather than post endless daft questions here?

Many thanks!

[skyship007]

Originally Posted by RollingThunder

Hi all, I'm new to the AWD forum so please forgive the newbie questions - I have googled (for hours) but haven't really found any definitive answers! I've owned many Volvos and currently have a '98 V70R so I'm happy pulling the engine etc apart I've pretty much just bought a '98 V70R auto AWD to join the stable, so my thoughts are focussed on the AWD system which is new to me.

My queries/concerns are these -
1. Is the AWD system really so intolerant of mixing new/old tyres on the same axle? I've read on the web that you can't simply replace one tyre on an axle, you have to replace the pair?! Is that really true or just scaremongering? I assume front/rear differences are ok?
2. I understand that the main reason for the AWD failing (apart from potentially differing wheel diameters) is that a (transfer box?) seal fails allowing fluid to escape causing the bearings to overheat? If that is correct, is there an 'upgraded' seal that can be fitted as a preventative measure? How easy is it to replace the bearings? I've noticed that most people disconnect the propshaft and drive it as a FWD car, but I'll want to retain the AWD if it does start to have issues.
3. Is the '98 auto AWD model more or less prone to these issues? The one I have 99% bought only has 110k miles up so is comparatively low mileage (for a Volvo lol).
4. Presumably the rear diff will need regular maintenance too - is any particular oil recommended? I don't mean what is in the owners manual - what have owners found to be the best oil?
5. Finally (!!!) Do we have a resident AWD system guru that I can bug rather than post endless daft questions here?
Many thanks!

I like the early V70 diesels and did look at the AWD models, I'm no expert but here are a few thoughts:

1/ Yes and No, as no ABS / EBD system likes different tyres or tread depths. No different to any similar car and better than most.
2/ It all depends on the condition of the box and they are no different to other AWD estate cars. If you buy a dripper and changing the box oil plus a LM box oil stop leak fails, it could get expensive. Mileage is no indication of transmission system wear. Noise, slick operation, service records and oil leaks are.
3/ Don't know
4/ Volvo OEM from Rufe (FRF Swansea dealer) or Skandix. The only upgrade would be to look at the Liqui Moly oil guide to see which transmission oils it lists. Volvo box oil is an HC synthetic but the LM 75W90 is the real McCoy German standard (G4) full synthetic.
5/ No idea, but you might ask in the caravan section, as horse box towing is best done with an AWD in winter etc. The V50 and 70 AWDs can tow 2 horses, but my 40 is max weight with one.

If you buy any car with a tow bar already fitted, make 100% sure the clutch is not slipping, as that is the main cause of most premature gearbox failures. Not changing or topping up the oil often enough (Every 100K km with the big cam belt service for new oil) is the second main reason.

[RollingThunder]

Brilliant, thanks for that. I was starting to see tumbleweeds lol.

I've actually bought the car now, its due to be delivered next week. Thanks for the tip about the fluid - I'll get in touch with Rufe to get the correct stuff. Looks like I'm going to have to learn about the other stuff as I go along

Thanks again, Sam

[Thanatos]

My queries/concerns are these -

1. Is the AWD system really so intolerant of mixing new/old tyres on the same axle? I've read on the web that you can't simply replace one tyre on an axle, you have to replace the pair?! Is that really true or just scaremongering? I assume front/rear differences are ok

its not advisable and will kill the awd system fast you nrmally have to keep the tyres with in 2mm accross both axles so a puncture at 5mm will mean 4 new tyres

2. I understand that the main reason for the AWD failing (apart from potentially differing wheel diameters) is that a (transfer box?) seal fails allowing fluid to escape causing the bearings to overheat? If that is correct, is there an 'upgraded' seal that can be fitted as a preventative measure? How easy is it to replace the bearings? I've noticed that most people disconnect the propshaft and drive it as a FWD car, but I'll want to retain the AWD if it does start to have issues.

main issues on ours are the cv joints that go dry and cost £350 each from volvo but can be bought for less check what size prop is on the car when you get it as i have 3 and only 1 fits my car auto ones are longer then manual

3. Is the '98 auto AWD model more or less prone to these issues? The one I have 99% bought only has 110k miles up so is comparatively low mileage (for a Volvo lol).

depends how its been treat in earlier life

4. Presumably the rear diff will need regular maintenance too - is any particular oil recommended? I don't mean what is in the owners manual - what have owners found to be the best oil?

i have had mine 5 years and not needed to do anything

5. Finally (!!!) Do we have a resident AWD system guru that I can bug rather than post endless daft questions here?

can contact me anytime i have rebuilt mine including modifying mine as i was using it have a read of http://www.volvoforums.org.uk/showthread.php?t=177363

[upv5]

Read this post http://www.volvoforums.org.uk/showthread.php?t=201540
The Service Bulletin I attached shows how the system works and advises to always put the larger diameter tyres on the front.

John

[Thanatos]

The p2 awd system is different as it's the haldex system and our on the 1998 is a viscous coupling but the early p2 used the same not sure what year it changed though


Sorry Jon just reread your post and the builtin makes sense actually never seen that one when's it from

[RollingThunder]

Originally Posted by Thanatos

5. Finally (!!!) Do we have a resident AWD system guru that I can bug rather than post endless daft questions here?

can contact me anytime i have rebuilt mine including modifying mine as i was using it have a read of http://www.volvoforums.org.uk/showthread.php?t=177363

Thanks mate, appreciate this. Hopefully i won't need to bug you too much but I'm sure I'll have the odd query...

Nice car btw

[Thanatos]

no problem its getting there with the additional bits like indicators

new Bigger turbo to go on and I have an R eecu for it which it runs perfectly well with at the moment just runs out of puff withteh little turbo I got

[Paffel]

I'm also happy to chime in if you have any AWD questions there Sam.

[RollingThunder]

Thanks Thanatos and Paffel, appreciate that Haven't even looked at the car yet sadly as I've been too busy! Hoping to get a chance to wash/inspect it later today...