slippage in drive after rebuild

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david30101

New member
After installing transmission after rebuild. I found that all forward gears have little or no movement of truck. Reverse is strong and holds good. Slips real bad in drive, 2 and 1 positions. I have a new accumulator piston with double seals. I did the air test on the kickdown servo and reverse servo, all was good. I did clean the valve body and made sure everything is back together same way. It has all new clutches and bands. What gives?
 
Bands are set properly. I have a IH service manual and was going through the troublshooting section. Proper band adjustment wasnt brought up. I was looking at the application chart for the bands and clutches, it shows that in drive and forward gear selections that the bands are not applyed, im thinking its the rear clutch. I did put new seals on the piston that activates it. According to the table that the rear clutch is the only thing applyed when selector is placed in drive (breakaway). I May end up pulling the transmission again. I do have another complete rear clutch assembly from another transmission that was never dissasembled. Ill just swap the plates and clutches over. But not touch the piston.
 
Were all parts typically found in a rebuild kit actually installed? Including all clutch plates and both bands using new items?

Were the clutch assemblies installed upon the pump and then air pressure tested for proper actuation?

Were all four "pressure points" tested with compressed air before the valve body was re-installed?

Have you verified the pump and input shaft assembly as noted in this thread, posts #2>6?:

http://www.forums.IHPartsAmerica.co...t-407-tf727-variations-parts-differences.html

Swapping parts in from another transmission when you don't know for certain what is actually wrong is a very lost cause. These units are certainly not difficult to rebuild if the various resources we've mentioned many times are used.
 
I already know what was wrong, I pinched a seal while assembling the rear clutch piston. It seemed to work ok with air pressure, but not good enougth to power the truck. I have it tore back apart. I think you have the year messed up. You were saying the transmission you have that is "newer" pn 492448 c91?. That is the exact same one I have in my Travelall which came out of a 74 or 75 model, not a 78. Anyhow.. Mine also has the part throttle downshift. Btw, I cant use the other rear clutch. Its the "older" style (74) and is completly differnt then the (late 74 or 75) transmission im trying to fix. I guess ill have to hunt down some rear clutch piston seals.
 
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