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TH350 speedo drive seal leaking

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Old 11-17-2011, 07:53 AM   #1
Stephen Irons
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Default TH350 speedo drive seal leaking

Hi

I've noticed that there is a very small escape of fluid from the speedo drive on the trans of my '78. So, can someone tell me what the arrangement there is for a seal etc? Is it possible/easy to change the seal with the trans in situ etc. Any “how tos”?

At the moment the car has a single cable from ‘box to speedo head which I may be changing if and when I re-furb the transducer. But, I’m a bit reluctant to fiddle with the cable if the leak may be exacerbated!

Thanks!
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Old 11-17-2011, 08:19 AM   #2
BHRIG
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From under the car check to see if
The retainer which holds speedometer cable to the transmission has an "O" ring which is probably leaking... If this is where the problem is it is an easy fix......
Remove retainer, 1 bolt, and slowly pull on cable to remove retainer.
There should be an "O" ring, or a grove for one, near the outside of the retainer.
Replace and reinstall....clean area around and watch for leaks.
No, you don't have to remove transmission to replace this "O" ring.....
Good luck

Last edited by BHRIG; 11-17-2011 at 08:25 AM. Reason: omission
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Old 11-17-2011, 07:04 PM   #3
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Default speedo gear housing

stephen- in addition to the o ring on the speedo gear housing (called a " gear sleeve") there is an internal cup type seal that seals the speedo gear shaft. costs less than $5 at NAPA. be sure to notice how the orig. was installed and replace accordingly. i replaced both on my 78 and still had a small leak so i put a small amount of silicone on the o ring and on the threads of the gear housing then screwed te speedo cable back on. sometimes the keeper will not keep the gear housing from moving- not much room here to work but you have to use needle nose or similar to hold the housing while you tighten the round coble "nut". i marked mine then screwed the cable to the housing then put the gear housing in the hole then installed the small retainer plate. let the silicone set up before using- a couple hours. same for 77-81 i think and maybe other yrs. as well. hope this helps. its a pain in the butt on a good day.as it is right over the crossmember with a 350 trans.
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Old 11-17-2011, 07:12 PM   #4
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I clean all surfaces with laquer thinner or similar before applying silicone- especially up in the hole. You may call me if you like -Joel 251-945-5735
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Old 11-18-2011, 12:34 AM   #5
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Default Housing!

Replace the speedo gear housing.This part solved my never ending speedo leak for good! http://www.transmissioncenter.org/sp...ar_housing.htm [IMG][/IMG] There is some sort of seal in that housing that is not easily repaired.It's better to just install a new one.....Aloha's
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Old 11-18-2011, 06:45 AM   #6
Stephen Irons
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Thanks guys!

Sounds like "fun"! There certainly is not a great deal of space up there... I'd already decided I'd need to drop the exhaust front pipe just to unscrew the cable I'll do some investigating soon!
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Old 11-18-2011, 01:47 PM   #7
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The seal is easy to replace but the housing itself could have some other issue so I agree- EBAY #200651200109 will put one to your door USPS for $10.50 + $2.89. Budon,t forget what I said about the silicone- used SPARINGLY it CAN be your friend. I,m going to order 1 of those speedo housings myself! 78 mahogany lonebull- out!
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Old 11-07-2015, 03:09 PM   #8
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Default 82 speedo cable

Hi Everyone- I'm back to the '82 speedo cable I cried about a couple months ago. The problem turned out to be in the tranny, that little gear broke. I got the bolt and keeper out but the little plate is stuck. Should I apply a little persuasion and pry it out? Thx
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Old 11-07-2015, 03:18 PM   #9
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Quote:
Originally Posted by stevic View Post
Hi Everyone- I'm back to the '82 speedo cable I cried about a couple months ago. The problem turned out to be in the tranny, that little gear broke. I got the bolt and keeper out but the little plate is stuck. Should I apply a little persuasion and pry it out? Thx

Plate? Are you talking about the aluminum (sometimes plastic) driven gear housing that the 6mm bolt and retainer hold in? if so just pry on it or you can grab the threaded end (after wrapping a double thickness rag around it) and give it a little twist while pulling on it. It'll pop out pretty easy.
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