TH400 leak question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

OUbesto · 08-21-2017, 02:33 PM

I am getting a slight fluid leak that builds up around the speedometer cable where it enters the tranny housing. What's interesting is that there are no drips where the cable actually attaches to the tranny but the red fluid accumulates on the larger round band which is about an inch away from the housing. This round band can be finger turned to a point and then I used a pliers and tried to tighten a little but it doesn't seem to lock down. Since I'm looking at this area from my garage floor while using a floor jack, I can't get a real good look at how the speedo cable secures into the tranny housing. It almost looks like there is a small screw in the metal where speedo goes into tranny housing.

Can anyone tell me how the speedo cable is attached to the tranny housing? Also, any thoughts why the fluid would accumulate by the band and not where it enters the tranny housing?

67 chevelle · 08-21-2017, 03:05 PM

most trany guys call it a bullet , has an inner and outer o ring , sounds like the inner o ring is shot , they are cheep , just get a bullets

just the seals
http://www.ebay.com/itm/Speedo-LEAK-...-/310409441700

wbc409 · 08-21-2017, 03:08 PM

The speedo cable has a nut that threads onto the housing at the tranny. The housing is round, and holds the speedo drive gear in place. The speedo drive gears are replaceable, and different tooth counts depending on rear axle ratio and tire diameter. There should be a rubber o - ring that seals the housing to the tranny.

**70STOVEBOLT** · 08-21-2017, 04:25 PM

There is also a lip type seal that goes into the cable adapter and seals against the speedo driven gear. It is held in by a wire clip. You can buy a seal kit that comes with the o-ring for the adapter as well, I paid $8 on eBay.

OUbesto · 08-21-2017, 06:40 PM

Thanks to all. Ordered the o rings from eBay and will tackle the job this weekend!

Lanman1972 · 08-21-2017, 06:54 PM

Keep us posted on how it turns out! Thanks

08-21-2017, 02:33 PM	#1
OUbesto Registered User Join Date: Oct 2015 Location: Lincolnshire, IL / Burlington, WI Posts: 209	TH400 leak question I am getting a slight fluid leak that builds up around the speedometer cable where it enters the tranny housing. What's interesting is that there are no drips where the cable actually attaches to the tranny but the red fluid accumulates on the larger round band which is about an inch away from the housing. This round band can be finger turned to a point and then I used a pliers and tried to tighten a little but it doesn't seem to lock down. Since I'm looking at this area from my garage floor while using a floor jack, I can't get a real good look at how the speedo cable secures into the tranny housing. It almost looks like there is a small screw in the metal where speedo goes into tranny housing. Can anyone tell me how the speedo cable is attached to the tranny housing? Also, any thoughts why the fluid would accumulate by the band and not where it enters the tranny housing? __________________ 1970 C-10 CST, LWB, 402/400, A/C

08-21-2017, 03:05 PM	#2
67 chevelle Registered User Join Date: May 2013 Location: WEST PALM FLORIDA Posts: 1,174	Re: TH400 leak question most trany guys call it a bullet , has an inner and outer o ring , sounds like the inner o ring is shot , they are cheep , just get a bullets just the seals http://www.ebay.com/itm/Speedo-LEAK-...-/310409441700 __________________ 68 Long Fleet , ly6 , turbo 350 , 3-5 drop , original paint , front discs 67 Small window , 7 foot bed , tweaked 6.0 LSX 2004R Medium Olive 58 Apache fleet , 235 , offy intake , dual exhaust , 4 on the floor , red/white 69 Long Fleet , Custom , 6.0, 4l60 , AC , Medium Olive Last edited by 67 chevelle; 08-21-2017 at 03:10 PM.

08-21-2017, 03:08 PM	#3
wbc409 Registered User Join Date: Mar 2015 Location: st cloud mn Posts: 163	Re: TH400 leak question The speedo cable has a nut that threads onto the housing at the tranny. The housing is round, and holds the speedo drive gear in place. The speedo drive gears are replaceable, and different tooth counts depending on rear axle ratio and tire diameter. There should be a rubber o - ring that seals the housing to the tranny.

08-21-2017, 04:25 PM	#4
70STOVEBOLT Senior Member Join Date: Jun 2005 Location: Winona Lake, IN Posts: 6,414	Re: TH400 leak question There is also a lip type seal that goes into the cable adapter and seals against the speedo driven gear. It is held in by a wire clip. You can buy a seal kit that comes with the o-ring for the adapter as well, I paid $8 on eBay. __________________ 70 C/10 SWB 402/TH400/3.73 "The Needy Beast" 200,000 Mile Club Disc Brake Club Owner installed options: Front Sway Bar Power Steering Power Brakes Cigar Lighter Courtesy Lights Deluxe Side Markers Wiper Delay Sliding Rear Window Power Windows Power Locks Sniper EFI 2015 Silverado 1500 LS 4.3/6L80/3.23 lowered 2" front & rear

08-21-2017, 06:40 PM	#5
OUbesto Registered User Join Date: Oct 2015 Location: Lincolnshire, IL / Burlington, WI Posts: 209	Re: TH400 leak question Thanks to all. Ordered the o rings from eBay and will tackle the job this weekend! __________________ 1970 C-10 CST, LWB, 402/400, A/C

08-21-2017, 06:54 PM	#6
Lanman1972 Registered User Join Date: Dec 2013 Location: Omaha NE Posts: 620	Re: TH400 leak question Keep us posted on how it turns out! Thanks __________________ 1972 C10 Custom Deluxe LWB, 402/400, PS, PB, A/C, Highlander, Hugger / White 1971 C10 Cheyenne LWB (SWB), 350/350, PS, PB, A/C, Dark Olive / White.



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