TH350 Blowing Fluid

Chad E532 · 01-15-2009, 07:04 PM

Towards the end of the 2008 season I went to a deeper gear spinning the engine/trans a little higher. Now I have a problem of transmission fluid blowing out of the plastic vent in the case. I see that TCI offers a reservoir for this problem on a TH400 or Glide but not for the TH350. Also, I remember seeing a super comp rail that had the vent line plumbed into the pan with AN line (aftermarket case).
I would like to just run a line from the vent to the pan, but I am not sure if this will fix the problem since any transmission case pressure will then have no way (that I know of) to release.
I am open to any ideas to keep my under carriage and garage floor clean.
Thanks,
Chad

ss3011 · 01-15-2009, 08:25 PM

Two things to look at. Make sure the oil level is correctly set. Too high of an oil level might cause the oil to come out the breather. Make sure you have the correct dipstick and tube for the type of pan you have. Factory Deep pans are to lower the oil level, not increase the amount of oil. Deep pan transmissions from the factory get different dipsticks, and tubes that lower the hot full mark on the stick, compared to the pan flange. Also another typical source of oil out the breather comes from cross leaks across the pump halves. Those surfaces are bolted together, and need to be flat, so they seal on each other. If the breather passage in the pump gets flooded with line pressure oil, or converter feed oil, it can over load the circuit, and the extra will blow out the breather. You could also put a small line on the breather fitting, and run it into a vented plastic bottle tie wrapped to the transmission crossmember, that will help keep the overflow off the track or garage floor.

Chad E532 · 01-15-2009, 09:40 PM

Thanks SS3011,
I am running a TCI deep cast pan but with a stock dip stick. I typically run the fluid at the "add a pint" mark but maybe that is too high.

I am going to have to pull it out and replace the front pump gasket and seal just to be sure and then I can run a tap into the vent hole to add some plumbing.

Mark Yacavone · 01-15-2009, 10:29 PM

T200's are just as bad or worse.
The catch cans are ok until you forget to empty it .
I just braze a short nipple, made out of a piece of brake tubing, up near the top of the filler tube, and run a small hose from the vent, up to it.

Joe Toller · 01-16-2009, 11:47 PM

I actually do that on my demo derby car trannies, works great.

SSGN · 01-18-2009, 08:22 PM

Quote:

Originally Posted by Mark Yacavone

T200's are just as bad or worse.
The catch cans are ok until you forget to empty it .
I just braze a short nipple, made out of a piece of brake tubing, up near the top of the filler tube, and run a small hose from the vent, up to it.

That is a great idea,but how does the trani vent to atmoshere when useing a locking dipstick.I am thinking you would build pressure in the trans.

Mark Yacavone · 01-18-2009, 09:02 PM

Quote:

Originally Posted by SSGN

That is a great idea,but how does the trani vent to atmoshere when useing a locking dipstick.I am thinking you would build pressure in the trans.

The old non-locking dipsticks I use don't seal very well!

SSGN · 01-19-2009, 09:46 PM

Thanks for the info Mark,muchly appreciated.We are looking at some changes over the winter and that is one of them.Have a good winter.

ss3011 · 01-19-2009, 11:16 PM

If you make the modification that Mark is suggesting, drill a hole through the dipstick tube just below the seal/o-ring that seals in the case. That will stop the straw effect, that could cause oil to spew out of the top of the dipstick tube. Also if you look at the early style, non locking dipstick, you will notice that the seal up by the handle has a notch in it. It also acts like a vent.

67ss · 01-20-2009, 08:43 AM

I've had this problem on a 350 and a 400. A new pump in the 400 fixed the problem which may likely be the same problem you are having. These old pumps get slightly worn/warped and casue fluid to bleed across the circuits as previously mentioned, but I also run a universal catch can made by CSR. We had the trans out so we pulled the plastic vent tube and just barely enlarged the hole for 1/4" copper tubing. Pushed tubing through and flared it so it would seat just like the plastic line. Also used a little JB weld to seal it. Then I just used some clear tubing from Lowe's from the trans to the can. The catch can comes with an 1/8" NPT snaplock type fitting but it was going to take a much larger hole to tap it for the fitting and there isn't much room there to drill in the 400 so we just opted for using the copper line.

01-15-2009, 07:04 PM	#1
Chad E532 Member Join Date: Jul 2008 Location: Lindstrom MN Posts: 156 Likes: 7 Liked 54 Times in 7 Posts	TH350 Blowing Fluid Towards the end of the 2008 season I went to a deeper gear spinning the engine/trans a little higher. Now I have a problem of transmission fluid blowing out of the plastic vent in the case. I see that TCI offers a reservoir for this problem on a TH400 or Glide but not for the TH350. Also, I remember seeing a super comp rail that had the vent line plumbed into the pan with AN line (aftermarket case). I would like to just run a line from the vent to the pan, but I am not sure if this will fix the problem since any transmission case pressure will then have no way (that I know of) to release. I am open to any ideas to keep my under carriage and garage floor clean. Thanks, Chad

01-15-2009, 08:25 PM	#2
ss3011 Senior Member Join Date: Feb 2002 Location: Southeast Michigan Posts: 903 Likes: 68 Liked 237 Times in 112 Posts	Re: TH350 Blowing Fluid Two things to look at. Make sure the oil level is correctly set. Too high of an oil level might cause the oil to come out the breather. Make sure you have the correct dipstick and tube for the type of pan you have. Factory Deep pans are to lower the oil level, not increase the amount of oil. Deep pan transmissions from the factory get different dipsticks, and tubes that lower the hot full mark on the stick, compared to the pan flange. Also another typical source of oil out the breather comes from cross leaks across the pump halves. Those surfaces are bolted together, and need to be flat, so they seal on each other. If the breather passage in the pump gets flooded with line pressure oil, or converter feed oil, it can over load the circuit, and the extra will blow out the breather. You could also put a small line on the breather fitting, and run it into a vented plastic bottle tie wrapped to the transmission crossmember, that will help keep the overflow off the track or garage floor.

01-15-2009, 09:40 PM	#3
Chad E532 Member Join Date: Jul 2008 Location: Lindstrom MN Posts: 156 Likes: 7 Liked 54 Times in 7 Posts	Re: TH350 Blowing Fluid Thanks SS3011, I am running a TCI deep cast pan but with a stock dip stick. I typically run the fluid at the "add a pint" mark but maybe that is too high. I am going to have to pull it out and replace the front pump gasket and seal just to be sure and then I can run a tap into the vent hole to add some plumbing.

01-15-2009, 10:29 PM	#4
Mark Yacavone Veteran Member Join Date: Mar 2002 Location: Miles From Nowhere Posts: 7,738 Likes: 2,838 Liked 4,995 Times in 1,899 Posts	Re: TH350 Blowing Fluid T200's are just as bad or worse. The catch cans are ok until you forget to empty it . I just braze a short nipple, made out of a piece of brake tubing, up near the top of the filler tube, and run a small hose from the vent, up to it. __________________ The sun will shine in my back door someday March winds will blow all my troubles away.... (Hunter / Garcia / traditional)

01-16-2009, 11:47 PM	#5
Joe Toller Senior Member Join Date: Jan 2009 Location: Lewistown, Montana Posts: 550 Likes: 78 Liked 4 Times in 4 Posts	Re: TH350 Blowing Fluid I actually do that on my demo derby car trannies, works great.

01-19-2009, 09:46 PM	#8
SSGN Senior Member Join Date: Feb 2006 Posts: 644 Likes: 128 Liked 140 Times in 51 Posts	Re: TH350 Blowing Fluid Thanks for the info Mark,muchly appreciated.We are looking at some changes over the winter and that is one of them.Have a good winter.

01-19-2009, 11:16 PM	#9
ss3011 Senior Member Join Date: Feb 2002 Location: Southeast Michigan Posts: 903 Likes: 68 Liked 237 Times in 112 Posts	Re: TH350 Blowing Fluid If you make the modification that Mark is suggesting, drill a hole through the dipstick tube just below the seal/o-ring that seals in the case. That will stop the straw effect, that could cause oil to spew out of the top of the dipstick tube. Also if you look at the early style, non locking dipstick, you will notice that the seal up by the handle has a notch in it. It also acts like a vent.

01-20-2009, 08:43 AM	#10
67ss Junior Member Join Date: Jan 2008 Posts: 29 Likes: 0 Liked 0 Times in 0 Posts	Re: TH350 Blowing Fluid I've had this problem on a 350 and a 400. A new pump in the 400 fixed the problem which may likely be the same problem you are having. These old pumps get slightly worn/warped and casue fluid to bleed across the circuits as previously mentioned, but I also run a universal catch can made by CSR. We had the trans out so we pulled the plastic vent tube and just barely enlarged the hole for 1/4" copper tubing. Pushed tubing through and flared it so it would seat just like the plastic line. Also used a little JB weld to seal it. Then I just used some clear tubing from Lowe's from the trans to the can. The catch can comes with an 1/8" NPT snaplock type fitting but it was going to take a much larger hole to tap it for the fitting and there isn't much room there to drill in the 400 so we just opted for using the copper line. __________________ Chad Harris 67 Chevelle SS http://mysite.verizon.net/harrisracing