420 Auto transmission fluid.

[BookerME]

The 420 has been sat unused for well over 10 years. I’m in the process of putting it back on the road. As part of the re-commissioning, I’m considering replacing the transmission fluid in the auto gearbox. I wondered if it may have deteriorated over time – say a bit like brake fluid is prone to?

According to the manual, it’s a Model 8. It says drain the oil, remove and clean the pan and adjust the bands. The first two might be a bit messy but should be easy enough for me. With the third, I’m somewhat reluctant to start messing around with something I don’t fully understand.

Has anyone got any views or experiences on this please? Many thanks in advance.

Mac Booker.

[PPV]

I used to have a Vauxhall Ventora with auto. I would suggest a pan clean and change of fluid after it has been standing for so long. I was surprised how much crud had settled in mine. If not used in the period there may be gumming up of some of the pathways etc but I personally would not play around with it until fluid changed and then having run it as if you did play with it and it did not work well then you could not be sure it was something you did or it was like that before.
Regards,

[RichardSEL]

"8" probably refers to a BW8. Those were in use into the early series 1 XJ6 too
Change both ATF and filter. You may find two small metal pieces magnetised in the pan to collect filings. Check to see whether you have any swarf
I say may coz I've not done mine yet that's been standing also for many years.

The fluid is not latest Dextron. It's type "G" or "F". For parts suggest: www.automaticchoice.com
p230 of their .pdf catalogue. There's no drain plug on a BW8 but can be added from the kit they sell. New gasket required once pan taken down (and warm old ATF runs up your arms)

Or use a suction pump to get most out. You won't get out what's in the torque convertor.

Any use?

[BookerME]

Thanks Richard, that’s all good info to take on board.
I’d seen that it was going to need a new gasket if I took the job on and wondered where I might get one.
I’d crawled underneath to see if I could spot a drain plug and couldn’t find one anywhere or any reference to one in the workshop manual either. It’s crazy that one wasn’t fitted – even if you do have to take the pan off to properly/fully service it. I guess they never imagined back in the day that anyone would actually do all that themselves!
On balance, I think I will change the fluid though if it’s been sat there all that time.

[RichardSEL]

"It's sealed for life, sir!" was the mantra given by dealers to any enquirers such as ourselves. Enforced by there being no drain plug

Even Vag were saying that for their Tiptronic (by Aisin Warner now made in China) sensitive to crud boxes up until five years ago. Course, that's got nothing to do with box failure or slippage causing £££s of added service work due to ATF breakdown
VW now say 60k is recommended (that was started coz VW US just went ahead and announced their own recommendation knowing what cack "sealed for life" was.

Think Jaguar are now saying 80k (?) for their XJ8 series (ZF's 5HP24).
But for the BW8 or 12 don't think anything was published (?)

[BookerME]

Richard, I agree, I know what you mean. Despite all the ‘sealed for life’ blurb, I had mine changed in my XKR when it got to 65,000 miles (I was too chicken to do it myself).

It seemed like a no-brainer really and all things considered, it wasn’t that expensive. A darn site cheaper than having it fail anyway. My thinking was it just HAD to have deteriorated over that time and I was absolutely sure I noticed the difference when I drove it up the road afterwards – well, that could have all been in my mind of course!

Anyway, the Daimler 420’s workshop manual says change it every 21,000 miles.
My bet is it might just have been changed once since 1969 – but probably never!
My original concern – maybe unwarranted – was that if it’s been sat there unused for over 10 years, it can’t have been good for it. I know brake fluid definitely won’t survive that time and will absorb moisture from the atmosphere. Would transmission fluid be that different? I don't know. The mighty Daimler's been in a dry garage all that time – but even so....

[RichardSEL]

>> Anyway, the Daimler 420’s workshop manual says change it every 21,000 miles.

Thanks for that, whether BW8 or 12, it's info I'll follow.
Despite my XJ6 series 1 only ever recording 24k

And get the ATF sump plug kit fitted -- this is pic of a BW12 sump with plug added.
(think this pic is a pre-made replacement pan though, can't remember where I found it)

[Tintin]

That's a pic of the BW12 sump pan fitted to my Series 1. When I took the pan off for an earlier fluid change I had this drain hole and magnetic drain plug fitted. The FR corner of the pan is its lowest point. It makes easy work of partial fluid changes to keep the old stuff well diluted.

Robbie