th400 second gear intermitent

gmonde · 05-04-2009, 06:28 PM

transmission guys:
last week had my th400 transmission miss second gear several times ,but it was intermitent to where i was able to get 3 full passes out of thee eight atemps(you could feel it hit and then the motor hits the chip) ,get back to the pits and put it second and the gear held (flash the converter to 4000 in second) sometimes work and sometimes not,take the trans out bring it to my builder and tear it down,the trans is perfect no clutches burned,fluid red,checked the spags (witch i thought for sure would be the problem) but they look ok
my questions:can a sprag roll over and not break the outer race,is it possable that it could just not lock up
is it possable the converters sprag is bad and note the converter has only 4-5 % slipage

full manual tci valve body

any help would be greatful gmonde

63corvette · 05-04-2009, 06:47 PM

First thing to check is the shifter and cable. Any slop at all change the cable. It may be going past or not quite getting to the right spot in the valve body every time.
Cables or sloppy linkage has caused more problems to not be a real issue.
Been there done that and felt stupid afterwards after pulling a trans 3 times taking it apart 3 times then fixed by changing the cable.
My 2 Cents

gmonde · 05-04-2009, 07:16 PM

after the second pass attempt thats what i did,jacked the car up and make sure the cable was adjusted and didnt go past the detent when shifting ,,,,i wish it was that gmonde

greg fulk · 05-04-2009, 07:24 PM

what shifter do you have? We had a Hurst pro matic in one of our cars it did the same thing...it was a ratchet style & would not catch the notch sometimes! Sent the shifter back & go a new 1 no more trouble.

gmonde · 05-04-2009, 07:35 PM

hurst quarter stick,solid gate operation gmonde

63corvette · 05-04-2009, 08:14 PM

Just checking the detent is OK but I did the same thing 3 times before changing the cable.
Cables cause more problems than people think. If it is several years old I would still look at it. As a cable gets older it will get loose on the compression and stretch.
Like I mentioned earlier pulling the tranny out and apart 3 times with no problems found but changing the cable made me feel pretty dumb a few years back. The cable looked good and I thought it was good but changing it sure did fix the problem.
My 2 Cents

Alan Roehrich · 05-04-2009, 08:16 PM

Yes, it is possible to roll a sprag and not break an outer race.

The sprag in the converter would not just affect one gear.

Do not do stall tests, loading the converter and not allowing it to release by launching the car will kill the converter.

Is this a new transmission, a new valvebody, a fresh rebuild?

gmonde · 05-05-2009, 06:39 AM

this trans has 75 pases on it and worked flawless last season,tried a couple converters in this unit this year and went back to the converter that was used last year,and lost second gear,like i said we tore this down and it looked perfect ,clutches not even burned,the steels have no signs of chatter or burning (if it was a presure issue you would think it burn clutches)upon inspection of the sprag it worked as it should but there where a few small marks on the outer race but considered normal,
but if the sprag rolled wouldnt second gear not operate at all? or will it roll back and opreate normal until the load was recreated ??? gmonde

Alan Roehrich · 05-05-2009, 07:03 AM

Have you tried actually replacing the sprag and the outer race?

gmonde · 05-05-2009, 11:05 AM

i will change out the sprags and race before it goes back together,you just like to see something obviously wrong with a componet before throwing parts at it and hopes of repairing the problems as we all know it cost $$$ to get up to the track,to find out it didnt solve the problem

thanks for all the replys gmonde

05-04-2009, 06:28 PM	#1
gmonde Senior Member Join Date: Nov 2007 Posts: 615 Likes: 56 Liked 165 Times in 59 Posts	th400 second gear intermitent transmission guys: last week had my th400 transmission miss second gear several times ,but it was intermitent to where i was able to get 3 full passes out of thee eight atemps(you could feel it hit and then the motor hits the chip) ,get back to the pits and put it second and the gear held (flash the converter to 4000 in second) sometimes work and sometimes not,take the trans out bring it to my builder and tear it down,the trans is perfect no clutches burned,fluid red,checked the spags (witch i thought for sure would be the problem) but they look ok my questions:can a sprag roll over and not break the outer race,is it possable that it could just not lock up is it possable the converters sprag is bad and note the converter has only 4-5 % slipage full manual tci valve body any help would be greatful gmonde

05-04-2009, 06:47 PM	#2
63corvette Senior Member Join Date: Mar 2007 Location: Canyon, Tx Posts: 552 Likes: 128 Liked 359 Times in 103 Posts	Re: th400 second gear intermitent First thing to check is the shifter and cable. Any slop at all change the cable. It may be going past or not quite getting to the right spot in the valve body every time. Cables or sloppy linkage has caused more problems to not be a real issue. Been there done that and felt stupid afterwards after pulling a trans 3 times taking it apart 3 times then fixed by changing the cable. My 2 Cents

05-04-2009, 07:16 PM	#3
gmonde Senior Member Join Date: Nov 2007 Posts: 615 Likes: 56 Liked 165 Times in 59 Posts	Re: th400 second gear intermitent after the second pass attempt thats what i did,jacked the car up and make sure the cable was adjusted and didnt go past the detent when shifting ,,,,i wish it was that gmonde

05-04-2009, 07:24 PM	#4
greg fulk VIP Member Join Date: Jan 2003 Location: jackson Posts: 1,165 Likes: 0 Liked 5 Times in 3 Posts	Re: th400 second gear intermitent what shifter do you have? We had a Hurst pro matic in one of our cars it did the same thing...it was a ratchet style & would not catch the notch sometimes! Sent the shifter back & go a new 1 no more trouble. __________________ Greg Fulk 308 308X P/SA "ALL AMERICAN"

05-04-2009, 07:35 PM	#5
gmonde Senior Member Join Date: Nov 2007 Posts: 615 Likes: 56 Liked 165 Times in 59 Posts	Re: th400 second gear intermitent hurst quarter stick,solid gate operation gmonde

05-04-2009, 08:14 PM	#6
63corvette Senior Member Join Date: Mar 2007 Location: Canyon, Tx Posts: 552 Likes: 128 Liked 359 Times in 103 Posts	Re: th400 second gear intermitent Just checking the detent is OK but I did the same thing 3 times before changing the cable. Cables cause more problems than people think. If it is several years old I would still look at it. As a cable gets older it will get loose on the compression and stretch. Like I mentioned earlier pulling the tranny out and apart 3 times with no problems found but changing the cable made me feel pretty dumb a few years back. The cable looked good and I thought it was good but changing it sure did fix the problem. My 2 Cents

05-04-2009, 08:16 PM	#7
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,116 Likes: 1,573 Liked 1,832 Times in 415 Posts	Re: th400 second gear intermitent Yes, it is possible to roll a sprag and not break an outer race. The sprag in the converter would not just affect one gear. Do not do stall tests, loading the converter and not allowing it to release by launching the car will kill the converter. Is this a new transmission, a new valvebody, a fresh rebuild? __________________ Alan Roehrich 212A G/S

05-05-2009, 06:39 AM	#8
gmonde Senior Member Join Date: Nov 2007 Posts: 615 Likes: 56 Liked 165 Times in 59 Posts	Re: th400 second gear intermitent this trans has 75 pases on it and worked flawless last season,tried a couple converters in this unit this year and went back to the converter that was used last year,and lost second gear,like i said we tore this down and it looked perfect ,clutches not even burned,the steels have no signs of chatter or burning (if it was a presure issue you would think it burn clutches)upon inspection of the sprag it worked as it should but there where a few small marks on the outer race but considered normal, but if the sprag rolled wouldnt second gear not operate at all? or will it roll back and opreate normal until the load was recreated ??? gmonde

05-05-2009, 07:03 AM	#9
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,116 Likes: 1,573 Liked 1,832 Times in 415 Posts	Re: th400 second gear intermitent Have you tried actually replacing the sprag and the outer race? __________________ Alan Roehrich 212A G/S

05-05-2009, 11:05 AM	#10
gmonde Senior Member Join Date: Nov 2007 Posts: 615 Likes: 56 Liked 165 Times in 59 Posts	Re: th400 second gear intermitent i will change out the sprags and race before it goes back together,you just like to see something obviously wrong with a componet before throwing parts at it and hopes of repairing the problems as we all know it cost $$$ to get up to the track,to find out it didnt solve the problem thanks for all the replys gmonde