Transmission fluid seepage - The 1947 - Present Chevrolet & GMC Truck Message Board Network

OregonNed · 05-20-2020, 09:18 PM

Looking for some advice for my truck. I have a '68 with a TH350 and a one-piece driveshaft. One of the first things I noticed with it is that when warm and parked on an incline with the front facing up, I get seepage of trans fluid from the front yoke. In researching it would appear that there are yokes with this sort of seep hole, (pressure relief?). Is there anything I can do to prevent these embarrassing puddles? Is it possible to get a new yoke with out this opening? thanks in advance.. Ned

**Boog** · 05-21-2020, 07:20 AM

Make sure the plastic vent tube at the top of the trans is open.

68Gold/white · 05-21-2020, 08:01 AM

The vent holes are only on the TH400's, as far as I know. The TH400's have a rubber "O" ring on the out put shaft, that seals inside the TH400 specific yoke. The TH400 yoke does not have splines inside it for the first 3-4 inches for this "O" ring to seal on.

Get under your pickup and push around on the yoke. There's a bushing the aligns the yoke. The bushing could have excessive wear allowing the yoke to be off center, allowing a slight leak, or your seal could be just leaking...

Richard2112 · 05-21-2020, 09:22 AM

Quote:

Originally Posted by 68Gold/white

The vent holes are only on the TH400's, as far as I know. The TH400's have a rubber "O" ring on the out put shaft, that seals inside the TH400 specific yoke. The TH400 yoke does not have splines inside it for the first 3-4 inches for this "O" ring to seal on.

Get under your pickup and push around on the yoke. There's a bushing the aligns the yoke. The bushing could have excessive wear allowing the yoke to be off center, allowing a slight leak, or your seal could be just leaking...

That's good information. As I recall, the TH400 didn't seem to have a seep problem. But I often hear of the 350 having this issue

OregonNed · 05-21-2020, 10:08 AM

Thanks for the advice given - I will check these out and try to nail it down,

05-20-2020, 09:18 PM	#1
OregonNed Registered User Join Date: Dec 2012 Location: Vancouver, Washington Posts: 1,644	Transmission fluid seepage Looking for some advice for my truck. I have a '68 with a TH350 and a one-piece driveshaft. One of the first things I noticed with it is that when warm and parked on an incline with the front facing up, I get seepage of trans fluid from the front yoke. In researching it would appear that there are yokes with this sort of seep hole, (pressure relief?). Is there anything I can do to prevent these embarrassing puddles? Is it possible to get a new yoke with out this opening? thanks in advance.. Ned __________________ 1968 Chevrolet C/10 LWB - 327, TH350 - 4/5 Drop

05-21-2020, 07:20 AM	#2
Boog laying low Join Date: Mar 2001 Location: Searcy, Ark. USA Posts: 13,513	Re: Transmission fluid seepage Make sure the plastic vent tube at the top of the trans is open. __________________ Boog 69 Chevy stepside, 358/T350, 4.11 posi, 4.5/4 drop, rallys, poboy driver primer is finer 91 Chevy sportside, Tahoe, Yukon & GMC Crewcab All GM..'nuff said. I stand for the flag and kneel at the cross

05-21-2020, 08:01 AM	#3
68Gold/white Registered User Join Date: Sep 2011 Location: Ark City, Kansas Posts: 3,405	Re: Transmission fluid seepage The vent holes are only on the TH400's, as far as I know. The TH400's have a rubber "O" ring on the out put shaft, that seals inside the TH400 specific yoke. The TH400 yoke does not have splines inside it for the first 3-4 inches for this "O" ring to seal on. Get under your pickup and push around on the yoke. There's a bushing the aligns the yoke. The bushing could have excessive wear allowing the yoke to be off center, allowing a slight leak, or your seal could be just leaking...

05-21-2020, 10:08 AM	#5
OregonNed Registered User Join Date: Dec 2012 Location: Vancouver, Washington Posts: 1,644	Re: Transmission fluid seepage Thanks for the advice given - I will check these out and try to nail it down, __________________ 1968 Chevrolet C/10 LWB - 327, TH350 - 4/5 Drop



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