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Old 04-23-2012, 01:10 PM
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T-400 w/brake problems

i have a th400 with a transbrake reverse valvebody it has worked flawlessly for about a year and a half went to town the other day and washed car got on it a couple times all seemed normal went back to garage and tried to back up and nothing solenoid clicked and nothing tried forward gears and clicked right in all three gears and solid shifts also went to end of dead end road and tried to turn around and slowly revved motor and at about 3600 to 3800 rpms it solidly engaged reverse as if you dropped it in reverse but not at idle or lower as it used to and it did not slip a bit so i tried to launch on tbrake and would not even tryt to hold so i launched off foot brake went into first and it kinda was soft but did engage and ran it thru the gears shifting at 7800 and all gears solid as before but still no reverse unless revved to 3800 took solenoid out for inspection and tested found nothing apparent wrong put back in then nothing no forward or reverse took tranny out and apart tottally found no seals or clutches fried sprag was solid and clean no chatter marks and rollers were all good also one way rollers also good clutch pack seals also good i am at a loss ordered new solenoid just in case have not gotten it yet can anyone please help with ideas am at a total loss have run out of ideas the converter is good also and no debris in tranny v/b or pan cleanest i have ever taken apart all ideas will b used and appreciated thanx in adavance please help at wits end never had nothing like this and this is first tbrake tranny but it worked awsome for quite awhile oh and trans temp never got above 160 it has a good cooler with its own fan and an autometer procomp gauge thanx again all ideas will b entertained sorry forgot to add fluid level was checked and full blucamaro1969

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Old 04-23-2012, 07:34 PM
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Quote:
Originally Posted by blucamaro1969
i have a th400 with a transbrake reverse valvebody it has worked flawlessly for about a year and a half went to town the other day and washed car got on it a couple times all seemed normal went back to garage and tried to back up and nothing solenoid clicked and nothing tried forward gears and clicked right in all three gears and solid shifts also went to end of dead end road and tried to turn around and slowly revved motor and at about 3600 to 3800 rpms it solidly engaged reverse as if you dropped it in reverse but not at idle or lower as it used to and it did not slip a bit so i tried to launch on tbrake and would not even tryt to hold so i launched off foot brake went into first and it kinda was soft but did engage and ran it thru the gears shifting at 7800 and all gears solid as before but still no reverse unless revved to 3800 took solenoid out for inspection and tested found nothing apparent wrong put back in then nothing no forward or reverse took tranny out and apart tottally found no seals or clutches fried sprag was solid and clean no chatter marks and rollers were all good also one way rollers also good clutch pack seals also good i am at a loss ordered new solenoid just in case have not gotten it yet can anyone please help with ideas am at a total loss have run out of ideas the converter is good also and no debris in tranny v/b or pan cleanest i have ever taken apart all ideas will b used and appreciated thanx in adavance please help at wits end never had nothing like this and this is first tbrake tranny but it worked awsome for quite awhile oh and trans temp never got above 160 it has a good cooler with its own fan and an autometer procomp gauge thanx again all ideas will b entertained sorry forgot to add fluid level was checked and full blucamaro1969
Did you check voltage to the transbrake switch & solenoid? Did you check all of the grounds?
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Old 04-23-2012, 07:47 PM
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yes 12.2 volts and moved ground and even temp run wire all way back to batt and no change even bypassed relay and ran straight voltage to solenoid and no change taking trans back apart to more closely inspect seals just gave them a qwik once over and feel may even just replace just to be sure but there were no chunks oe tears out of them whats weird is it just quit reverse first and had strong forward gears then when revved it would bld go to reverse as long as you held it that high and no slip but no transbrake action at all so i am leaning towards the solenoid but it seems to work and hold its position when i removed it and inspected it reinstalled and then no gears at all in any rpm level so i dont know buy thanx for the advice
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Old 04-24-2012, 06:41 AM
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Did you air check the rear band servo and check the rear band for wear?
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Old 04-24-2012, 07:19 AM
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just looked at the band looked ok but now you mention it the drum it rides on did have some minor wear grooves where band was applying would that cause it to go all at once? what gets me is the revving it and have it grab as if you jerked a normal trans into reverse at those rpms but after removing and putting solenoid back in lost everything just makes no sense i wished i would have found something broken it would have been easy from there but at least i get to learn this way maybe i will replace drum with new one also would that make the tbrake not engage and lock in 1st gear to launch it wont even try to hold it when it was working and with no reverse before this was working perfect when reverse wouldnt work tbrake wouldnt even attempt to hold put in first and engage button sloenoid would click and hold and car would just roll on as if nothing there thanx for the idea i am pulling it back apart and will inspect a little closer and will replace drum anyway will keep updating waiting on new solenoid before reinstall of trans for now thanx again and please keep ideas coming blucamaro1969
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Old 04-24-2012, 11:25 AM
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If it has minor wear it is fine. When you increase rpm you are increasing pressure and volume that is why is works at 3800. Put it back together and back in the car. You can have a friend you trust work the car from the top end on a lift or on jackstands while you operate the transmission, you can put in first, engage the solenoid by hand, and then relase. If it holds then the solenoid is shot, the transmission does not care how the solenoid engages as long as it is engaged. If it does not work take a line pressure test reading off the plug above and to the rear of the shift linkage. Should be between and depending on the brake and associated chart around 180-210psi. Any manufacture should have instruction posed online. If it is low then you have a pump issue or a leak witch is found by the air and line pressure test. You can also apply air to the reverse band servo in port with the Valvebody removed, about 40 psi will apply it and let you know if there is a leak. Also some transbrakes have you install a 1/4 check ball in the 1-2 accumulator servo area under the reverse band apply servo, make sure this is installed.

So is there only no reverse, no transbrake or flat out nothing at all without increased engine RPM? Line pressure should have been your first step, it will tell you everything.
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Old 04-24-2012, 12:04 PM
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first off i would like to say thank you for taking time to help i appreciate it very much. thank you just got my new solenoid in so will put that in also at first it had no reverse unless revved got it back to the shop and took out solenoid to inspect it and simply put .it back in then i had nothing but before that i had just run the dog snot out of it thru all 3 gears and shifted firm and no slip and trans temp normal thats what has me confused this trans worked great for about a year and a half or so but havent put but maybe 600 miles on it if that if it was a seal i think i would have other symptoms but have none going to air check it as soon as i get back there if it leaks then what? seals on the servo or ? oh and when i first noticed no reverse i tried the brake and it did not function would not hold the car or even try. as long as i held in the button the solenoid held its position so i really dont think it the solenoid but stranger things has happened to me and i will also check pressure have to run down a tester first and will post those findings after i get it back in the car. also when i found out reverse was not working i noticed going to first was not as solid as it had been almost as if fluid was low kinda slipped in but not slipping dont really know how to describe it but fluid level was fine even added a quart to make sur and no change but on the foot brake fisrt never slipped or gave any sign of trouble and manually put in second and third and no signs of trouble holding thats when i decided to play it safe and pull tranny out and apart to inspect it and found nothing broken burnt or torn thanx again for taking your time to help will try all advice blucamaro1969
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Old 04-24-2012, 12:27 PM
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How are you getting reverse? Putting it in reverse or putting it in neutral and then hitting the transbrake button. Most transbrakes have you put them in neutral and then hit the transbrake button. For reverse the rear band and direct clutch are on. For third forward and direct drums are on. So if there is a pressure probelm/leak I would most likely suspect a rear band or rear servo leakage (check ball missing that is driven into the case under the 1-2 accumulator will cause a huge pressure loss) if and only if third gear is perfect, just like I said before until you run a line pressure test you are troubleshooting this blindfold with you hand tied behind you back, I don't think you can fix it until you run a line pressure test!!

Also make sure you did not mix up the transbrake valve with the stock modulator valve!!!
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Old 04-24-2012, 01:42 PM
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the hole was tapped and threaded with a plug came in the kit until i removed solenoid all forward gears were perfect until i reinstalled solenoid will be puttn trans back in ina day or so then will pressure check it and let you know what the outcome is. could a defective solenoid act like this? it should not affect forward gears though i wouldnt think
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Old 04-24-2012, 02:03 PM
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Did you install a plug in the center support next to the right of center support bolt? That has to open to get reverse and is plugged when guys dual feed direct. With a transbrake or manual valvebody this does not get plugged to dual feed and is accomplished within the valvebody.
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Old 04-25-2012, 03:05 AM
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no plug. it has worked for a year and a half and then all of a sudden no reverse have not changed just drove it then no reverse removed solenoid and reinstalled then nothing no movement. also neutral then push button for reverse as long as i have it apart again i ordered a new rear band and replacing it also trying anything i can think of to fix this even though the old band still has all the writing and markings on if that matters pertaining to wear.
thanx for all the help so far
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Old 05-01-2012, 10:29 AM
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new update on this junk went thru entire tranny replaced all seals and orings and replaced rear band just to be sure measured old band thickness and new band and no difference so old band was good even changed the drum air checked it and it is working took tranny to local college and put it on there trans dyno and still no reverse all forward gears but no reverse unless you bring rpms way up then it is as if you dropped it from neutral it just bangs in and no slippage i think the valvebody is garbaged i even put a new solenoid on it and no difference all forward gears now work but will not even try to hold on the transbrake like its not even there and pressure was at 192 according to the dyno operator and temps never got above 190 so i guess i am off to buy another valvebody. oh and i disassembled the current v/b to inspect for stuck or possible debris and i could not tell if any were stuck all seemed to move as they should so if anyone has anymore advice before i spend more money on this junk please advise me on what i could check next i am totally lost thanx
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Old 05-02-2012, 06:34 AM
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See if you can send the v/b back to whoever you bought it from. Maybe they can test it and make a small change to get it working again.
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