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Transmission electrical plugs – beware the URO!

6K views 9 replies 7 participants last post by  43sqd 
#1 ·
Just so no one tries fixing a leaking transmission electrical plug with an inferior product........

After reading posts of the URO transmission electrical plug not being up to par, I got a MB plug to compare with the URO plug previously ordered from AutohausAZ. (Had previously ordered but not installed a URO for the lastest 722.6xx addition to the family, a ML320 with 165,000 mi)

A quick visual did not show any differences. A dimensional comparison of the plug bodies with calipers showed they were the same.

However, a dimensional check of the smaller O ring showed that the URO was thinner than the MB plug by about 20 thousands when installed on the plug. The upper O ring was also thinner.

Once the O-rings were rolled off the plug bodies, the size differences became clear. (see photo)

I speculate that the smaller O ring is critical to keep ATF out of the conductor plate shroud connection (a guess) and that the larger O ring keeps ATF from leaking to the outside of the transmission. A less tight fit of the URO plug may increase the chances of ATF leaking into the connector and wicking up to the Transmission Control Module.

Glad now of spending a few extra bucks on the MB plug. Just changed it out on the ML320 (which has a transplant tranny and heaven knows how many miles). Of course, the connector plug was wet with ATF on the electrical side, and the inelastic rubber O rings were red (factory original?) Also, the new MB connector plug was slightly difficult to get the center 7mm bolt to engage than compared to the last time I changed a plug on our E420 – with a URO. Suspect that the smaller O-rings make for easier seating, but inferior sealing. And, as luck would have it, I had ordered the S430 transmission plug replaced 3 years ago from AutohausAZ, so that (URO) is going to be replaced in during the upcoming tranny service.
 

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#2 ·
With them being under $20 at the dealer I have never seen an aftermarket one.

Thanks for showing the W163 members. Maybe Boca or AsianML can make this a sticky.
It is very important that the OEM MB one is used.
(I could, but I am not a moderator for this forum and do not want to offend Boca or AsianML)
 
#4 ·
The Uro adapter plug is not a good part - one of the very few autohausaz.com MB parts I have seen problems with.

I don't blame autohausaz.com on this one, as shown by the side-by-side comparison the parts are to all inspection "comparable" - it's just on that key execution of the o-rings the updated OE part is superior.

Keep the faith !
 
#6 ·
1 year life out or URO plug

I replaced a leaking plug with a URO plug less than a year ago. Then I saw a spot in the driveway where my wife parks her E55. When she returned home I did a complete inspection. The plug was Leaking! After reading this post I have ordered the genuine Mercedes part from Pelican parts. Its almost an embarrassing problem. Thanks all for the post!
 
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