Another TH400 leak
Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
There are 2 seals. One is an O-ring around the outer diameter of the large speedo gear insert. The other is a lip seal that seals the spinning inner shaft to the inner diameter (bore) of the insert. Tightening the speedo cable has no effect on leaks - there is no seal in the cable.
Thread Starter
Advanced
Joined: Oct 2019
Posts: 85
Likes: 7
From: UK
There are 2 seals. One is an O-ring around the outer diameter of the large speedo gear insert. The other is a lip seal that seals the spinning inner shaft to the inner diameter (bore) of the insert. Tightening the speedo cable has no effect on leaks - there is no seal in the cable.
Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
Nope. The speedo gear insert is above the pan fluid level. You'll get a few drops leaking when you remove the insert, so just put a drain pan under it when you yank it out.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
IF the inner lip seal on the TH400 is similar to the one on the TH350 then replacing it may or may not solve the leak depending on the condition of the old seal. I replaced mine when it was leaking only to find it still leaked. What I ended up doing was putting and o-ring under the lip portion of the the lip seal ( where a spring normally resides, Don't recall if this one had a spring or not), to force it tighter around the sealing area and that did the trick.
Thread Starter
Advanced
Joined: Oct 2019
Posts: 85
Likes: 7
From: UK
IF the inner lip seal on the TH400 is similar to the one on the TH350 then replacing it may or may not solve the leak depending on the condition of the old seal. I replaced mine when it was leaking only to find it still leaked. What I ended up doing was putting and o-ring under the lip portion of the the lip seal ( where a spring normally resides, Don't recall if this one had a spring or not), to force it tighter around the sealing area and that did the trick.
