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Old 03-01-2013, 02:38 AM   #26
BlackedOut67shorty
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Re: Speedo cable leaking?

And I thank you soo much for doing that. Just remember whenever ya need good deals on New parts I'm down the street, oh and the Speedo is more like 15 to 20 miles off, gotta find some time to get that bullet out and take it to the tranny shop. Hopefully I can start on it in the afternoon
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Old 03-01-2013, 10:56 AM   #27
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Re: Re : Speedo Gears & Ratios ?

Quote:
Originally Posted by VWNate1 View Post
Who's got a link to that chart ? .

My TH350 is reading almost *exactly* 10 MPH too fast.......

I just need a link but any other comments or helps would be great too .

TIA ,
My 68 with a 3 speed saginaw was showing somewhere around 53-55 at 60 mph. With a little luck and doing some reading I got mine right on the money without having to change the drive gear inside the transmission. I just counted the teeth on the driven gear and tried one with the next fewer teeth.

Example; The speedometer reads 66 MPH at an actual 60 MPH. 66 divided by 60 is 110% or 1.1. That means the driven year is rotating 1.1 times too fast. To slow it down, we must increase the number of teeth on it by 1.1. If it is a 40 tooth gear initially, a 44 tooth gear will be correct.

Conversely, if the speedometer is reading too slow, the driven gear speed must be increased, and less teeth on the gear would be required. In John's case, the speedometer was accurate before the gear change and the error caused by the gear change is known. 3.42 divided by 3.08 = 1.11. John needs to increase the driven gear's teeth by 1.11. If he has a 40 tooth gear, 40 x 1.11 = 4.44. Therefore, he would need a 44 tooth gear. http://www.bafb.org/1968firebird.org...articles16.htm

More reading...

http://www.thegearbox.org/catalog/it...82/3697857.htm

http://www.transmissioncenter.net/sp...n_______va.htm
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Old 03-01-2013, 11:11 PM   #28
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Thumbs up Re: Speedo cable leaking?

Great info ! THANX ! .
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Old 03-02-2013, 03:23 AM   #29
midniteblues
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Re: Speedo cable leaking?

thank you for the info
i'll havta take hs truck for a ride with a gps too get some real #'s an go from there

that is after he fixes the window
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Old 08-23-2013, 11:14 PM   #30
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Re: Speedo cable leaking?

Is this something that should have been replaced in a rebuild? Im leaking at the speedo cable as well. TH400. I just had the tranny rebuilt. I noticed the cable was loose so I tightened it up, i must not have tightened when i reinstalled the tranny. but I noticed another drop and some fluid on the crossmember.
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Old 08-24-2013, 09:18 AM   #31
midniteblues
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Re: Speedo cable leaking?

Quote:
Originally Posted by JointTech View Post
Is this something that should have been replaced in a rebuild? Im leaking at the speedo cable as well. TH400. I just had the tranny rebuilt. I noticed the cable was loose so I tightened it up, i must not have tightened when i reinstalled the tranny. but I noticed another drop and some fluid on the crossmember.

Im only guessing here but if a trans is rebuilt then a rebuild kit was ordered for it.
an once again i'm only guessing that the bullet seals shoulda been in the kit.
i've never rebuilt a trans but it only seems logical to replace all the seals.

even if it was supposed to be replaced i would still go back too the rebuilder an ask for either the seals (2 of them) or a complete new bullet.

be sure too count the teeth on the speedo gear or better yet take it with you most times the leak comes from a ring worn on the gear shaft.

these parts are/should be fairly inexpensive.but if you dont have a trans shop nearby they could be a lil' difficult too locate locally new.
of course they are availible everywhere online.
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Old 08-24-2013, 12:03 PM   #32
oldgoalie
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Re: Speedo cable leaking?

T-400 only uses a aluminum speedo gear housing, about 1 1/2 in diameter. There are different ones depending on the # of teeth the speedo gear has. They take just a small rubber seal which does come in a o/h kit. The gear will get a groove in it where the seal rides and seep a little. You can double up the seal, which will help. Best is to find a new gear. New housings are getting a little harder to find, it has been about 25 years ago GM quit building the 400 and most parts aren't being produced any more such as speedo housings. It is NOS or used. That being said I am sure the trans shop would fix it for you.
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Old 08-24-2013, 01:06 PM   #33
Tx Firefighter
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Re: Speedo cable leaking?

This is the seal that goes in a Th350 speedo bullet. Two bucks from Rockauto. The old and new seals on the box with part number. Made is USA seal too.



O ring for outside of the bullet. Tractor Supply in the hydraulic section. A baggie of them is under 2 bucks.



I press the seal in on my press to slip it in nice and straight without trauma to the seal. Bonus points for using an antique S-K Wayne socket as a press tool.



A dollop of grease on the gear.



Fresh o ring.


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