TH400 shift issues no 2-3 shift
TH400 shift issues no 2-3 shift I have a normal th400 that when I took it out it had a very soft reverse. 1-3 was fine forward. I found the direct cjutch smoked and the piston had a ripped seal. I thought cool this is it! So I looked over everything else quick, replaced the seal, fibers and steels and the wave plate as it was cracked. Put it all together and in the truck. Now I have reverse, and the 1-2 shift is good. 2-3 never seems to happen and the weird thing is that I don't have any engine braking in manual first. Any iseas of what I could have f***ed up? Governer maybe? Modulator is good (new) as is vacuum to it. Thanks! 
There is a ball in the case like in a bathtub around the middle are you sure its there ?
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This is a regular old th400, stock rebuild, no trans brake. It is in my 88 K3500 shop/plow rig that I lost the motor in recently and swapped in an 02 5.3L. All the rest of the drive train is stock. Thanks though.
Thats correct I think maybe Vince saw the part about no engine braking and some how concluded a transbrake.
I mentioned the ball because the OP seems to have two separate issues the no engine braking in manual low which would point to and issue with the LOW/REVERSE band and no 3rd which would point to the direct clutch drum. But they have a common path through that area of the case at that ball and since he has reverse I would have to assume that the two parts are working since they are both used to make reverse. So thats where I would be looking.
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When I first pulled the trans I was expecting a broken reverse band or a servo issue. We deal with this issue with 4L80E's all the time (GM tech). It did not have engine braking before I pulled it apart as well. When I didn't find an issue with the rev band then I started digging deeper and found the clutch/piston seal issue. Just weird that 3rd was solid before even with the smoked clutches. I will R&R the valvebody and check the check ball and the governer to see if the shaft is stuck or it spit out a spring. Thanks.
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Verdad Gallardo I would take a look at the center suport bolt and make sure all is tight there.
Last edited by FLT; Oct 22, 2009 at 07:29 AM.
Haha! I forgot that was in the sig. Never thought to check the center support bolt either. Now my brain is playing tricks on me. Did I tighten it? Did I put the check ball in? Maybe when I air checked the clutch I messed up the seal? ARGH!
pulled and checked the governer. It is ok. Check ***** are all in the correct locations, center support bolt is tight. Only thing I am finding without taking the trans apart is the plastic piston that is in the valve body is cracked. This is on top of the forward accumulator. According to the fluid chart this goes to the direct clutch. Could this cause my issue? Not broken but has a large crack though it. thanks.
Ok. Obviously I have messed up something in the direct clutch because after driving the truck home I now have no reverse again along with no 3rd still. Time to take it back out.
The cracked piston is definitely an issue. Get yourself an aluminum one to replace it. A leak in this area can cause issues with both 2nd and 3rd gears. This is due to the intermediate band circuit being on just the other side of the piston. I have seen issues when the wrong seal was installed and a leak was caused. Basically if you were to manually shift this trans it would hurt the band because oil would try to apply the band and vice versa.. So yes I definitely think you found your problem. Let us know how it turns out for you. Vince Bielanski
yea I put in the new piston and still didn't have 3rd. Drove it 20 mile from the shop to the house and when I got there reverse was gone again. I think the piston seal I put into the direct clutch might have an issue although it seemed to air check ok.
