T25 Automatic 090 Gearbox reverse gear clunk

[DjD]

Need some help - have a T25 camper B reg 1985 with 1.9cc petrol engine DG code and 090 autogearbox - all works fine when cold and warm but when hot (after 6 mile drive) engaging reverse from P and D gives a large shudder/clunk

Revs are 850rpm, new Dexron 2 ATF fluid level OK and drives well in all gears.

Just had the ATF changed with Castrol Dex 2 and after a day noticed that fluid was not red- but slightly brown - but smelt Ok no burnt smell.

The autoshift from 1-2 and 2-3 seems OK and can reach 70mph ok shifting from 2-3 is almost un noticeable but more of a slight surge from 1-2.

Some mention adjusting bands, others replacing valve seals in autobox which means dropping box and expense. Drives OK in forward and accelerates OK.

The only band to adjust is 2nd gear band in the Bentley manual.

If the diff had play it would also be a problem when cold ?

. HELP
Down in West Cornwall. Thanks

[Ian Hulley]

Welcome to the forum

Ian

[Aidan]

could be pinion bearing, change the diff oil and see what the magnet says

[DjD]

Thanks for advice - there seems to be no gearbox whine that would be associated with a pinion bearing problem but is hard to hear this with the noise of a VW

The clunk in engaging reverse only appears when engine is hot and we have driven 6+miles and no clunk when cool, warm. When cool, warm the auto transmission is smooth and P,D,R, N etc all seem smooth to engage.

As you select R when hot you get a shudder/clunk - occurs when going from P to R or N to R.

Perhaps it could be the oil pump in the autobox and lack of pressure ?
Or backlash /slack in diff more apparent when HOT ?

But will now change diff oil and have now some Fuchs Hypoid 90- will see what the magnet has picked up

thanks

[aruntaylor]

Hi
My auto box had this clunk when selecting reverse and then into D.
I drove it several thousand miles until one day it made a crunch, split a planetary diff gear and punctured the diff pan. Oil all over the campsite, and the AA home.

So, new diff from the states and a Cogbox rebuild.

The diffs are very expensive so maybe it worth removing the diff, changing the oil etc before t too late.

But then again, it will probably drive for another 20 years like that... My van is very heavy.

[DjD]

Arun

Thanks for help on this - did your problem only happen when hot after 6 miles or so and was ok when cold/warm

Difficult to get much help on the 090 3 speed in Uk more from Canada and USA
see the links below

I have to drop the diff sump pan after i have made a pan gasket as these are difficult to source - VW don't supply any more
the oil level is fine but the previous owner wasn't so hot on maintainence

I have changed auto pan seal/filter and ATF.


Some replies have mentioned slack in the CV joints and pinion bearing in the diff - the auto 3 speed seems fine otherwise

thanks
Dave

http://www.thesamba.com/vw/forum/viewto ... +planetary" onclick="window.open(this.href);return false;
http://www.josephpugh.com/?p=95" onclick="window.open(this.href);return false;
http://tech.bentleypublishers.com/forum ... 49&start=0" onclick="window.open(this.href);return false;
http://vanagonsyncroproject-herman.blogspot.com/" onclick="window.open(this.href);return false;
http://www.volkszone.com/VZi/showthread.php?t=741292" onclick="window.open(this.href);return false;

[aruntaylor]

Hi
I've just driven mine after new diff and box rebuild and it still has a clunk into reverse clunk into drive.
Just the way it is I suppose.
Probably going to be slack in the driveshafts? Not my diff as that is a brand new peloquin item. Cv joints will be my next job.

[DjD]

Some of the T25 /Vanagon forums suggest syringing in some CV grease into the CV joints - I will try this first before removal work
You can carefully syringe some Moly grease with a thin stiif pipe and syringe under the rubber gaiter on the drive shafts carefully

Surprised that you still have a clunk in reverse with rebuilt diff/autobox - check the engine mounts.
Does the clunk only happen when engine hot ?