TH350 Problem

Terry Cain · 10-23-2021, 07:45 PM

60's pretty good first pass off of trailer. second pass will slow about 3 on 60. Third pass will slow even more. Will slow as much as a tenth on 60. Everything has been pulled a part and check by several people. New valve body. New clutches (several times) Only thing that has not been replaced is the case. Can take the convertor and put it on another (spare) trans and it is very consistent on 60's. Any suggestions? Need to add. I can put spare trans in and use same dipstick on both trans so fluid level is the same.

Angelo DiTocco · 10-23-2021, 09:08 PM

do you have a pressure gauge for the trans?

Mark Yacavone · 10-23-2021, 09:49 PM

Do you have a temp gauge on the trans?

Terry Cain · 10-24-2021, 05:52 AM

Quote:

Originally Posted by Angelo DiTocco

do you have a pressure gauge for the trans?

160

Henrys Toy · 10-24-2021, 08:56 AM

Quote:

Originally Posted by Terry Cain

60's pretty good first pass off of trailer. second pass will slow about 3 on 60. Third pass will slow even more. Will slow as much as a tenth on 60. Everything has been pulled a part and check by several people. New valve body. New clutches (several times) Only thing that has not been replaced is the case. Can take the convertor and put it on another (spare) trans and it is very consistent on 60's. Any suggestions? Need to add. I can put spare trans in and use same dipstick on both trans so fluid level is the same.

Good Morning Terry,
I had a similar problem a few years back with a GM/Chevrolet PG case.
I had changed over from "sleeve type bushings" to Roller Bearings and followed the recommended clearance tightening and the trans would slow the car down as we started hot lapping the car. I loosened the "end play" about .003 to .005 overall and the problem stopped.
My spare Glide ( also a GM case) was set up with the recommended tighter clearence's and wouldn't slow down as it got hotter.
So is the case growing and tightening up or is it the front pump, maybe its an alum. drum or hub, sorry I don't have a exact answer, but I found running a little more end play clearence did "fix" my problem at the time.

Respectfully,
Henry Kunz 1534 H/SA

Terry Cain · 10-24-2021, 07:13 PM

It does have the aluminum stuff in it and also a new pump.

Mark Yacavone · 10-24-2021, 10:33 PM

I don't know about the 'glide but you don't want to loosen a T 350 up much. Keeping them snug helps them in the direct drum area.
I asked about the temp, because, if the converter is already on the loose side of things, the warmer fluid could hurt it.

ss3011 · 10-24-2021, 10:36 PM

You probably have a seal that is leaking , which is causing a clutch to drag . The hotter the fluid gets the greater the leak that is causing the clutch to drag . What type of ring seals do you have on the pump tower ? Typical types are cast iron with a locking feature or two types of plastic seals one solid , or the second type with a diagonal cut end . The best seal is the solid teflon .

Terry Cain · 10-25-2021, 07:21 AM

Quote:

Originally Posted by ss3011

You probably have a seal that is leaking , which is causing a clutch to drag . The hotter the fluid gets the greater the leak that is causing the clutch to drag . What type of ring seals do you have on the pump tower ? Typical types are cast iron with a locking feature or two types of plastic seals one solid , or the second type with a diagonal cut end . The best seal is the solid teflon .

Teflon and front pump has been out a zillion times. Not sure on temp but don't think that is the problem. Deep pan so it has an extra 2 qts. Sharver originally done trans yrs back. He plugged the coolant lines and did some drilling on pump to redirect fluid. The pump has been replaced and wondering if maybe that could be problem?

ss3011 · 10-25-2021, 09:38 AM

I have talked about this before , but deep pans are not designed to increase the cold fill volume , but to lower the fluid level away from the rotating parts . As fluid gets hotter it expands and if that expansion gets the fluid up into the rotating parts it will mix up like a milk shake . That is bad for windage and will also hurt pressure stability , lubrication , and cooling . A deep pan with 2 extra quarts of fluid in the trans will be even worse . Typically you need a re-calibrated dipstick which compensates for the deeper pan .
Since you have a problem with one trans and no problem with another , I still believe a leaking seal is more likely .

10-23-2021, 07:45 PM	#1
Terry Cain Senior Member Join Date: Feb 2008 Location: Georgetown, Indiana (close to Louisville, KY) Posts: 774 Likes: 530 Liked 230 Times in 106 Posts	TH350 Problem 60's pretty good first pass off of trailer. second pass will slow about 3 on 60. Third pass will slow even more. Will slow as much as a tenth on 60. Everything has been pulled a part and check by several people. New valve body. New clutches (several times) Only thing that has not been replaced is the case. Can take the convertor and put it on another (spare) trans and it is very consistent on 60's. Any suggestions? Need to add. I can put spare trans in and use same dipstick on both trans so fluid level is the same. __________________ Terry Cain ???? STK tcain19689585@gmail.com Last edited by Terry Cain; 10-23-2021 at 08:26 PM.

10-23-2021, 09:08 PM	#2
Angelo DiTocco Senior Member Join Date: Dec 2001 Location: NY, NY Posts: 750 Likes: 175 Liked 189 Times in 48 Posts	Re: TH350 Problem do you have a pressure gauge for the trans? __________________ Angelo DiTocco '98 Firebird SS/HA '98 Firebird B/SA

10-23-2021, 09:49 PM	#3
Mark Yacavone Veteran Member Join Date: Mar 2002 Location: Miles From Nowhere Posts: 7,780 Likes: 2,872 Liked 5,065 Times in 1,931 Posts	Re: TH350 Problem Do you have a temp gauge on the trans? __________________ "We are lucky we don't get as much Government as we pay for." Will Rogers

10-24-2021, 07:13 PM	#6
Terry Cain Senior Member Join Date: Feb 2008 Location: Georgetown, Indiana (close to Louisville, KY) Posts: 774 Likes: 530 Liked 230 Times in 106 Posts	Re: TH350 Problem It does have the aluminum stuff in it and also a new pump. __________________ Terry Cain ???? STK tcain19689585@gmail.com

10-24-2021, 10:33 PM	#7
Mark Yacavone Veteran Member Join Date: Mar 2002 Location: Miles From Nowhere Posts: 7,780 Likes: 2,872 Liked 5,065 Times in 1,931 Posts	Re: TH350 Problem I don't know about the 'glide but you don't want to loosen a T 350 up much. Keeping them snug helps them in the direct drum area. I asked about the temp, because, if the converter is already on the loose side of things, the warmer fluid could hurt it. __________________ "We are lucky we don't get as much Government as we pay for." Will Rogers

10-24-2021, 10:36 PM	#8
ss3011 Senior Member Join Date: Feb 2002 Location: Southeast Michigan Posts: 908 Likes: 70 Liked 238 Times in 113 Posts	Re: TH350 Problem You probably have a seal that is leaking , which is causing a clutch to drag . The hotter the fluid gets the greater the leak that is causing the clutch to drag . What type of ring seals do you have on the pump tower ? Typical types are cast iron with a locking feature or two types of plastic seals one solid , or the second type with a diagonal cut end . The best seal is the solid teflon .

10-25-2021, 09:38 AM	#10
ss3011 Senior Member Join Date: Feb 2002 Location: Southeast Michigan Posts: 908 Likes: 70 Liked 238 Times in 113 Posts	Re: TH350 Problem I have talked about this before , but deep pans are not designed to increase the cold fill volume , but to lower the fluid level away from the rotating parts . As fluid gets hotter it expands and if that expansion gets the fluid up into the rotating parts it will mix up like a milk shake . That is bad for windage and will also hurt pressure stability , lubrication , and cooling . A deep pan with 2 extra quarts of fluid in the trans will be even worse . Typically you need a re-calibrated dipstick which compensates for the deeper pan . Since you have a problem with one trans and no problem with another , I still believe a leaking seal is more likely .