TheSamba.com :: View topic - Automatic - leaking from final drive pan when filling gearbox

Thu May 22, 2025 10:45 am

Hi!

As the topic reads, my final drive pan is leaking oil when i refillwd with new ATF.

I noticed my van shifted gear really strange and i checked my oil level and it was zero.

I didnt notice any spill but filled up with new oil and the oil started to flow, not from the gearbox pan but under the final drive.

I understand the gasket is done, but i wonder, does the gearbox and final drive share oil?

I remember i had to fill it through a tube by losing a screw before. So if they share oil, good then i just need to change gasket. Or is it a seal inside that is broken so the oil travels to the final drive?

Best regards.
Johan

Thu May 22, 2025 10:58 am

First, head over to the transmission section of the FAQ. You will be able to quickly locate the information you need in the AT section.

https://www.thesamba.com/vw/forum/viewtopic.php?p=6236053#6236053

From your photo, it does look like the AT pan has a leak. When did you last check the level (prior to now)?

When you drop the AT pan, share some photos of what the fluid and debris in the pan look like.

Thu May 22, 2025 11:02 am

brickster wrote: First, head over to the transmission section of the FAQ. You will be able to quickly locate the information you need in the AT section.

https://www.thesamba.com/vw/forum/viewtopic.php?p=6236053#6236053

From your photo, it does look like the AT pan has a leak. When did you last check the level (prior to now)?

When you drop the AT pan, share some photos of what the fluid and debris in the pan look like.

Is it not the differential pan that is leaking? It is clearly red that i filled the transmission with. I changed oil in the differential last summer.

Thu May 22, 2025 11:12 am

Johanjons wrote: brickster wrote: First, head over to the transmission section of the FAQ. You will be able to quickly locate the information you need in the AT section.

https://www.thesamba.com/vw/forum/viewtopic.php?p=6236053#6236053

From your photo, it does look like the AT pan has a leak. When did you last check the level (prior to now)?

When you drop the AT pan, share some photos of what the fluid and debris in the pan look like.

Is it not the differential pan that is leaking? It is clearly red that i filled the transmission with. I changed oil in the differential last summer.

Yes, that's the differential pan that's leaking.

And, unfortunately, no, the differential and automatic sections DO NOT share the same fluid. You DO NOT refill the differential using the dipstick tube in your engine compartment. YES, there is a seal between the two systems that can break causing ATF and differential gear oil to mix.

You might have a bit of a headache to deal with.

Thu May 22, 2025 11:34 am

I’d degrease and pressure wash the entire drive train. It all looks like ass and a fluid will always drip from the lowest point.

And to clarify for someone in the future. There are 2 pans. One for the differential next to the engine case and one for the automatic. The differential is drained by removing the pan and filled with gear oil through the Allen plug in the side of the differential near the cv flange.

The automatic also doesn’t have a drain plug. You can remove the fill tube and drain quite a bit or the pan has to be removed. You can access the filter with the pan off and it’s filled from the engine compartment transmission dipstick tube. You use ATF Dexron was recommended, but some swear by Type F. I recall 3 QTs on a drain and refill.

Thu May 22, 2025 11:40 am

Johanjons wrote:
Is it not the differential pan that is leaking? It is clearly red that i filled the transmission with. I changed oil in the differential last summer.

It is, but I wanted to point out that your AT pan also looks like it was leaking prior to this. If you stopped driving in time, the transmission section of the transaxle may be OK. If you share the pan's contents before cleaning it would help diagnose its condition.

The final drive section may also be OK if you didn't drive with it empty for long. They are fairly hardy in comparison to the transmission section.

Thu May 22, 2025 11:59 am

Thanks guys!

I guess i have some work to do again.. :lol:

Any recommendation of seals and gasket of high quality that i should get before i remove everything. I am better of just changing everything i can when i remove it.

Thu May 22, 2025 12:19 pm

You may be at an advantage being in Europe, but I don't know. Hopefully someone from there will chime in.

Check this sticky out (Resources: Helpful Web Links & Vendors):
https://www.thesamba.com/vw/forum/viewtopic.php?t=128668

Thu May 22, 2025 1:36 pm

Johanjons wrote: Thanks guys!

I guess i have some work to do again.. :lol:

Any recommendation of seals and gasket of high quality that i should get before i remove everything. I am better of just changing everything i can when i remove it. To clarify, this is your Final Drive pan under the differential section of the Transaxle. If you added ATF to the Transmission Dipstick Tube, and it's now coming out THIS pan, you have indeed an issue.... :shock: :shock:

Thu May 22, 2025 2:14 pm

What people are trying to tell you....cryptically I might add :wink: ...is that you have ATF in the gear shift section and SAE gear oil in the differential section.

Most of these Borg Warner based transmissions for VW and some Audi of this era have two seals that need to be replaced at a reasonable interval.

In the early 90's VW/Audi had a technical data sheet that listed on very similar transmissions that thee seal should be replaced at an interval of 7 years or 70,000 miles. If either of the seals fail, the AtF fluid will get into the final drive fluid. What this causes is dilution of the anti-scuff qualities of the final drive hypoid oil. Within a couple hundred miles you can literally destroy the ring and pinion.

Yes, the gear oil can also get into the ATF sectio nand gum up valves and clutches but thats not permanent damage. ATF in thefinal drive oil IS permanent damage.

Any of this type of transmission has this issue with the seals. This included the 003 trans that went into type 3 and 4 cars and the 010 that went into the bay window bus.

The two seals are the mainshaft seal between the final drive and the gear section and the governor shaft seal loacted in the final drive section.

Back in those days it was about a $300 job because its not really invasive to the transmission.

Ray

Thu May 22, 2025 4:27 pm

For the differential pan you can just use silicone and do away with using the gasket. Some silicone compounds specifically mention they are good for use with gear oil. Whether you use a gasket or just silicone you want to flatten the area around the bolt holes in the pan, as people tend to tighten the bolts tighter when a leak shows up deforming the pan when doing so.

Do not use silicone on the transmission pan gasket, and don't go hog wild on the silicone you use on the differential pan gasket, just use a judicious amount.

Fri May 23, 2025 11:26 am

Wildthings wrote: For the differential pan you can just use silicone and do away with using the gasket. Some silicone compounds specifically mention they are good for use with gear oil. Whether you you a gasket or just silicone you want to flatten the area around the bolt hole in the pan, as people tend to tighten the bolts tighter when a leak shows up deforming the pan when doing so.

Do not use silicone on the transmission pan gasket, and don't go hog wild on the silicone you use on the differential pan gasket, just use a judicious amount.

When I was wrenching full time (late 80's early 90s) and doing 10 a week, I would invert the pan bending with a small ball peen hammer like;
https://enkaytool.com/888-2-mini-ball-pein-hammer-...4e7e4b7a0a
I guess anything like a CV ball would work but the intent was to keep the pressure even and proper without over doing the torque.

Fri May 23, 2025 11:29 am

The back to back seals have likely failed majorly.

Fri May 23, 2025 11:45 am

ALIKA T3 wrote: The back to back seals have likely failed majorly.

Yep....its a common issue with all of this "type" of transmission whether its Vanagon, Type 2, Type 3 or Type 4....and also in some of the watercooled VW and audi automatics.

I had this problem twice over about a five year period on my VW 412 back in the 80's. The original transmission one day...ate the transmission at 60 mph. The shop guy showed me the dissected parts. The differential oil was contaminated by ATF for an unknown period of time and the pinion shed a couple teeth....violence insued.

I still did not know why this had happened at that point in time. I was young and there were no books on 411/412. I bought a good used automatic out of a wreck and rolled on down the road. Three years later...same thing.

The problem is/was that its hard to find exact seal material and lip design that works for both oil types.

It used to be a bigger problem back in the day but I think seal materials have improved. Its still a problem though.

Ray

Fri May 23, 2025 11:47 am

When the internal seals between the final drive and the automatic side fail, the automatic fluid typically flows into the final drive so if you remove the final drive plug (17mm), reddish-brown oil will pour out as it will have the AT fluid mixed in with the hypoid/diff oil.

If you remove the plug and find the final drive oil level at it's normal level and the oil is still a normal colour, then the internal seals probably haven't failed and the leaks are external - from the pans, or somewhere else.

I had this happen with my 003 when I was having the 010 rebuilt back in 2019. One day after starting the Bus up I noticed a reddish brown pool under the Bus. I immediately shut it off. When I removed the diff plug, about a quart of reddish brown oil flowed out and there was no red automatic transmission fluid showing on the dipstick.

Mon May 26, 2025 11:56 am

Thanks for all the information everyone. I will do some ordering of new gaskets, seals and some other stuff now and check what can be done.

Saw a guy selling a automatic transmission on a facebook group in worst case.

Will update as soon as have identified the issue.

Thanks.

Tue Jun 03, 2025 12:53 pm

Hello again,

I have been searching the internet for the correct seals that you are refering to "Back to Back seals", feels like all sites have had different names for them but I found that according to VanCafe, that refer them to Transmission-Differential-seal, they state that in the Bently Workshop Manual, it is refered to the "Pinion seal"

https://vancafe.com/automatic-transmission-differe...9WYiq1oEyT

The pinion seal can luckily be found at BrickWerk - do you think this is the correct one to be replaced? https://brickwerks.co.uk/product/autobox-seal-t3/

PS i also found this blogpost which pretty much described my situation :D https://gowesty.com/blogs/article-library/automati...RMFvGqYDRR

Tue Jun 03, 2025 2:01 pm

Yes, that's the correct seal, and you'll need two. Notice that each vendor lists the VW part number (089409529D) on the product page.