T5, auto hesitates changing into 4th gear then clunk

[ImmortalT5]

Hi guys I have a 2008 transporter and it has just started revving and losing power every time it goes into 4th gear then slams into gear but every other gear is fine,
also after a little while doing that all of the ‘PRDS’ are all highlighted and tiptronic doesn’t work but that part goes away once off and on, can’t see fault codes either.
What should I do??
Thanks for the help in advance

[Rebuild]

Is it slipping(ie providing some drive) or is it going into neutral, with the revving? kms?Any oil/filter changes?
The first is flaring, and if it's a regular occurence, it will eventually burn up the clutch plates or more inside.
Most flaring with these gearboxes, occurs on the 2-3 and 3-4 change
Mine did flare early on years back on the 2-3, maybe 3 or 4 times only.
I have been doing my own filter and partial oil changes.Supposedly these gearboxes are sealed for life, which is BS
Just recently had my gearbox repaired for thumping into drive at 160K km, not much change from $3500
The Torque Converter Auto (NOT DSG) T5 thumps into drive when cold

Get it to a good auto trans place to diagnose.

[Sunny43.5]

As rebuild says ignore the Sealed for life BS {wish I had } ours had similar issues at 60000 as VW were not going to do a service we kept driving until complete failure at around 110000 turns out the original problem was caused by a partialy blocked filter just inside the box for the cost of 15 bucks for a new seal 45 bucks for a new filter and the new fluid I doubt ours would have failed completly .

[ImmortalT5]

I have only had it about 2 years and it’s up to 215,000km now, been doing oil and filter changes but never did transmission service, thought it was sealed for life,
It provides some drive trying to go out into gear I back off the accelerator to make it a smoother gear change but impossible to get up hills at the moment just keeping it in 3rd gear

[ImmortalT5]

My father is a diesel mechanic and he says maybe I have a leak?
So I’m thinking of trying to top it up but can only find drain plug so far

[ImmortalT5]

Also do you think that this could be linked?
When going into 3rd gear it’s like half way through 3rd it goes into another gear?
It’s like there are 2 gears for 3rd

[ImmortalT5]

But display still says ‘3’ even though I can feel it changing gear again

[Rebuild]

been doing oil and filter changes but never did transmission service

i did mean gearbox oil and filter.....

Sounds like it's flaring. IIRC, feels like it's half way between gears then thumps into next gear type thing

You can check the level reasonably easily.
Engine MUST be running and warm, on level ground
remove gearbox sump plug 5mm allen key.There is a tube up inside that sets the level, you won't lose all the oil. Wear gloves or be careful, hot oil
Oil should only drip out, if at all.There is a spec oil temp of 40C, but i never bother, just make sure gearbox is warm.
If low, filler is up on side of gearbox.Some more info here
How to change T5 Auto Gearbox Oil - The Brick-yard - Page 1

Gearbox oil is G055025 spec IIRC. VW sell the genuine stuff.

[ImmortalT5]

Thanks for all of the help!
I have added some Penrith full synthetic atf and it has gotten a little better but still slipping going to have to do a full service
The filler hose broke off inside hole and has been changed before because lack of o-ring 🙄
Filter wasn’t changed last time so....

[ImmortalT5]

Also my filler was at the top of the gearbox
Is that normal??

[Rebuild]

Maybe the fill location changed on later models.
As i said, i think you should seek the opinion of a transmission specialist

[jets]

Thanks for all of the help!
I have added some Penrith full synthetic atf

Do not start mixing oils, use the VW oil.

[ImmortalT5]

How often should you service auto trans?
Mine was last serviced 35k ago

[ImmortalT5]

So it has been getting stuck in 5th gear and very little power and tiptronic can’t make it change either, got engine light on and error po735
Changed fluid and filter and it was better for a second but then pretty much back to bad, it isn’t as bad now but still bad,
Does anyone know what the transmission sensors are called?
Shops only have “speed sensors”

[Rebuild]

i planned on doing partial changes once i started, every 75K km or so.Now gearbox is fixed, next oil and filter around 235K

i guess you've seen this or similar
17119/P0735/001845 - Ross-Tech Wiki