th400 second gear intermitent - Page 2

Tom Goldman · 05-05-2009, 11:30 AM

Greg,I'm assuming you are using the smooth race 34element sprag. ....It's very unlikely you hurt the sprag, altho I've had one or two spin the inner race on the direct drum.......? are you using an aluminum drum?,very possible to spin a race on some of them ....Hard to find since the race is pressed onto the splines on the drum. ....Other than a sheared center support bolt,which feeds second gear, Id be looking at the valve body.....Tom

gmonde · 05-05-2009, 12:15 PM

its not a 34 element ,we counted 17,but the replace ment will be the 34 element one ,that could be the issue gmonde

Henry S · 05-05-2009, 01:37 PM

What rings are you using for the center support? teflon or steel? I had a similar problem where a teflon ring was smashed in the ring groove. caused similar problem i think it was temp sensitive, hot would fail, cold was ok. Good idea to replace the cable regularly.

gmonde · 05-05-2009, 06:05 PM

teflon rings and they looked good they where not stuck in the grooves,but if it was a presure issue i would think it would show in the clutch pack, burned or marked clutches and or steels gmonde

Tom Goldman · 05-05-2009, 09:02 PM

The sealing rings on the center support are for the direct clutches and the sprag lube circuit ....they dont affect 2nd gear. ...... .the intermediate brake clutches in the case are actuated thru the center support anchor bolt....400's have been prone to sealing ring issues at the center support for years . ....some prefer teflon tings, others hard chromed iron rings. both work well when the drum stays off the ring lands ......ATI has a modified support with a floating bearing machined between the ring lands that helps support the weight of the direct drum, and keeps it from dragging on the ring lands ,which is really important with a stock iron drum at high rpm.,altho you really should have an aluminum direct drum for your application. ......Tom

west coast · 05-05-2009, 10:14 PM

It is your sprag if it does not hold no second gear. You said you have a 17 element which is stock they do not hold up to alot of power a couple of people make the double elements I used the Hughes never had another problem had to do it on a friday night at a divisional in Seattle. The tell tale sign of this is you hit the chip. I have ran S/G and S/ST for years with this combo.

Jeff Stout · 05-05-2009, 10:59 PM

The $2.00 snap ring that holds sprag in place is broke. I just went through this 3 months ago.On the street it worked great but twice at the track no second. If you guys watch Passtime my car is the Monte from the episode of AZ Fastest street cars in which it had no second and I thought I put it into neutral from coming down from a large wheelie.Sent meatl trash throughout the whole trans.
Jeff

SS Engine Guy · 05-05-2009, 11:06 PM

When the sprag rolls it does not come and go in my experience. Stock sprag is really bad about rolling the elements. Should roll one way but not the other. Good call on the snap ring/spiral ring holding the sprag. Back when we ran 400's the ring was tigged in place.

gmonde · 05-06-2009, 06:39 AM

the snap ring was in place,i will upgrade the sprag to the 34 element ,and try it out ,like mentioned it all looks real good ,no metal chunks,presure testsed the clutch pack for clamping presure ,checked detent for valvebody spool operation,tom your right should have the aluminum drum, but it is not in the budget for this month,thanks for the replys ,all of the info very helpful

gmonde

ss3011 · 05-06-2009, 07:43 AM

If your 2nd sprag has been slipping, it probably has hurt the surface finish on both the inner and the outer races. The surface finish is critical to the ability of the sprag to hold torque. The outer race is easy to replace. The inner one is ground true after being pressed on the drum, and should not be replaced. Best practice is get a different/new drum that is in good condition. Also make sure you get a 400 drum instead of a 4L80-E drum. The balance procedure on the 4L80 part might have compromised it's ability to be able to spin at high RPM. OK for a truck, iffy for a race car.

05-05-2009, 11:30 AM	#11
Tom Goldman VIP Member Join Date: Jan 2003 Location: Allentown,PA Posts: 2,477 Likes: 892 Liked 883 Times in 237 Posts	Re: th400 second gear intermitent Greg,I'm assuming you are using the smooth race 34element sprag. ....It's very unlikely you hurt the sprag, altho I've had one or two spin the inner race on the direct drum.......? are you using an aluminum drum?,very possible to spin a race on some of them ....Hard to find since the race is pressed onto the splines on the drum. ....Other than a sheared center support bolt,which feeds second gear, Id be looking at the valve body.....Tom __________________ Tom Goldman 1500 SG , 1506 STK Last edited by Tom Goldman; 05-05-2009 at 04:01 PM.

05-05-2009, 12:15 PM	#12
gmonde Senior Member Join Date: Nov 2007 Posts: 615 Likes: 56 Liked 165 Times in 59 Posts	Re: th400 second gear intermitent its not a 34 element ,we counted 17,but the replace ment will be the 34 element one ,that could be the issue gmonde

05-05-2009, 01:37 PM	#13
Henry S Junior Member Join Date: Aug 2007 Posts: 83 Likes: 11 Liked 19 Times in 7 Posts	Re: th400 second gear intermitent What rings are you using for the center support? teflon or steel? I had a similar problem where a teflon ring was smashed in the ring groove. caused similar problem i think it was temp sensitive, hot would fail, cold was ok. Good idea to replace the cable regularly.

05-05-2009, 06:05 PM	#14
gmonde Senior Member Join Date: Nov 2007 Posts: 615 Likes: 56 Liked 165 Times in 59 Posts	Re: th400 second gear intermitent teflon rings and they looked good they where not stuck in the grooves,but if it was a presure issue i would think it would show in the clutch pack, burned or marked clutches and or steels gmonde

05-05-2009, 09:02 PM	#15
Tom Goldman VIP Member Join Date: Jan 2003 Location: Allentown,PA Posts: 2,477 Likes: 892 Liked 883 Times in 237 Posts	Re: th400 second gear intermitent The sealing rings on the center support are for the direct clutches and the sprag lube circuit ....they dont affect 2nd gear. ...... .the intermediate brake clutches in the case are actuated thru the center support anchor bolt....400's have been prone to sealing ring issues at the center support for years . ....some prefer teflon tings, others hard chromed iron rings. both work well when the drum stays off the ring lands ......ATI has a modified support with a floating bearing machined between the ring lands that helps support the weight of the direct drum, and keeps it from dragging on the ring lands ,which is really important with a stock iron drum at high rpm.,altho you really should have an aluminum direct drum for your application. ......Tom __________________ Tom Goldman 1500 SG , 1506 STK

05-05-2009, 10:14 PM	#16
west coast Senior Member Join Date: Dec 2008 Location: Rainy Washington Posts: 609 Likes: 12 Liked 223 Times in 73 Posts	Re: th400 second gear intermitent It is your sprag if it does not hold no second gear. You said you have a 17 element which is stock they do not hold up to alot of power a couple of people make the double elements I used the Hughes never had another problem had to do it on a friday night at a divisional in Seattle. The tell tale sign of this is you hit the chip. I have ran S/G and S/ST for years with this combo.

05-05-2009, 10:59 PM	#17
Jeff Stout VIP Member Join Date: Dec 2001 Location: phoenix Posts: 1,486 Likes: 66 Liked 704 Times in 281 Posts	Re: th400 second gear intermitent The $2.00 snap ring that holds sprag in place is broke. I just went through this 3 months ago.On the street it worked great but twice at the track no second. If you guys watch Passtime my car is the Monte from the episode of AZ Fastest street cars in which it had no second and I thought I put it into neutral from coming down from a large wheelie.Sent meatl trash throughout the whole trans. Jeff

05-05-2009, 11:06 PM	#18
SS Engine Guy Member Join Date: Sep 2003 Location: usa Posts: 256 Likes: 1 Liked 1 Time in 1 Post	Re: th400 second gear intermitent When the sprag rolls it does not come and go in my experience. Stock sprag is really bad about rolling the elements. Should roll one way but not the other. Good call on the snap ring/spiral ring holding the sprag. Back when we ran 400's the ring was tigged in place.

05-06-2009, 06:39 AM	#19
gmonde Senior Member Join Date: Nov 2007 Posts: 615 Likes: 56 Liked 165 Times in 59 Posts	Re: th400 second gear intermitent the snap ring was in place,i will upgrade the sprag to the 34 element ,and try it out ,like mentioned it all looks real good ,no metal chunks,presure testsed the clutch pack for clamping presure ,checked detent for valvebody spool operation,tom your right should have the aluminum drum, but it is not in the budget for this month,thanks for the replys ,all of the info very helpful gmonde

05-06-2009, 07:43 AM	#20
ss3011 Senior Member Join Date: Feb 2002 Location: Southeast Michigan Posts: 909 Likes: 70 Liked 239 Times in 114 Posts	Re: th400 second gear intermitent If your 2nd sprag has been slipping, it probably has hurt the surface finish on both the inner and the outer races. The surface finish is critical to the ability of the sprag to hold torque. The outer race is easy to replace. The inner one is ground true after being pressed on the drum, and should not be replaced. Best practice is get a different/new drum that is in good condition. Also make sure you get a 400 drum instead of a 4L80-E drum. The balance procedure on the 4L80 part might have compromised it's ability to be able to spin at high RPM. OK for a truck, iffy for a race car.