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Old 04-06-2014, 08:30 PM   #1
cwilkie
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TH400 Leak fixed..new problem. Please Help.

I was finally able to get my TH400 to stop leaking. It was the speedo housing o-ring and speedo gear drive seal. Well I replaced those and it stopped leaking. Great... So I thought.

After a few miles with a smile on my face I noticed my speedometer making a winding noise. I removed the speedo cable from the dash and the noise was still there but not too bad.

I thought it was the speedo so I grabbed a known working speedo from my stash and it still made the noise but not as loud. Next I removed the Speedo cable from the truck and removed the cable to clean and grease it. When I reinstalled it the noise was still there but not as bad.

I am leaning towards the speedo gear housing being the problem but visually the housing and gear look fine. It seals so no leaks.

Has anyone had a similar problem like this before.

I want to get this issue resolved because my 17 year old nephew has been asking me all winter to let him use my truck for his prom. Well I agreed and his prom is this coming Saturday.
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1968 Chevrolet Stepside
BB 396 w/TH400

1972 Chevrolet 3/4 Ton 4x4
BB 496 w/TH400
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Old 04-06-2014, 08:34 PM   #2
airdale94
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Re: TH400 Leak fixed..new problem. Please Help.

You could have a kink in your cable. I wouldn't think if it was the gear that the sound would travel that much.
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Old 04-06-2014, 08:43 PM   #3
cwilkie
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Re: TH400 Leak fixed..new problem. Please Help.

The cable it just the right lenth. I actually tried two. The th400 cable and another one I have laying in the the garage. The noise did not start until I put a new o ring and seal on the speedo gear housing. The are no kinks and does not appear to have any extreme bends.

This is a weird issue. Any help is greatly appreciated.
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1968 Chevrolet Stepside
BB 396 w/TH400

1972 Chevrolet 3/4 Ton 4x4
BB 496 w/TH400
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Old 04-06-2014, 10:46 PM   #4
luvbowties
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Smile Re: TH400 Leak fixed..new problem. Please Help.

Quote:
Originally Posted by cwilkie View Post
I was finally able to get my TH400 to stop leaking. It was the speedo housing o-ring and speedo gear drive seal. Well I replaced those and it stopped leaking. Great... So I thought.

After a few miles with a smile on my face I noticed my speedometer making a winding noise. I removed the speedo cable from the dash and the noise was still there but not too bad.

I thought it was the speedo so I grabbed a known working speedo from my stash and it still made the noise but not as loud. Next I removed the Speedo cable from the truck and removed the cable to clean and grease it. When I reinstalled it the noise was still there but not as bad.

I am leaning towards the speedo gear housing being the problem but visually the housing and gear look fine. It seals so no leaks.

Has anyone had a similar problem like this before.

I want to get this issue resolved because my 17 year old nephew has been asking me all winter to let him use my truck for his prom. Well I agreed and his prom is this coming Saturday.
Try another cleaning-and-greasing. Sometimes heavier(or lighter) grease than that designed for it will work better. Is cable long enough to try a slight re-route? Try using nylon tie straps to shorten/reposition the sharper bends. HTH,
Sam
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Old 04-07-2014, 12:13 AM   #5
cwilkie
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Re: TH400 Leak fixed..new problem. Please Help.

I will try that. I am going to go get some white grease tomorrow. I will soak the cable in a coffee can with transmission fluid for a day and then coat in in white lithium grease then reinstall and hope for the best.
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1968 Chevrolet Stepside
BB 396 w/TH400

1972 Chevrolet 3/4 Ton 4x4
BB 496 w/TH400
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