Mike, we have spoken on the phone a couple times in the past regarding Allison stuff (Probably 2 years ago).
Sorry for the long post.
I have a 1987 fullsize Blazer with a 700R4. It has the auxiliary valve body.
The trans was bad when I bought it. The converter was broken where the input shaft splines mesh, and the trans had 130k miles on it. I pulled it and rebuilt it with new clutches and steels, including the Raybestos 3-4 clutch pack. I put a newer valve body on it (a known working 1990 valve body). I also installed a Transgo 700 Jr. I replaced the input drum/input shaft. The pump had to be machined because of scoring. It has a new converter as well (obviously). This was the first 700R4 rebuild I have done.
When it first went back together it was great. The pressures were about the same as those recorded below. Good shift points, downshifts were appropriate, lockup working correctly, temps NEVER over 160 (measured at the pressure port above the manual linkage). I drove it around a bit, city and highway. I put about 150 miles on it and then....
One morning it started short shifting. 1-2-3-4 all by 20 mph. NO downshift with part throttle or WOT. Up in to 4th with the converter locked at 20-25 miles per hour and doing the lock-unlock-lock-unlock at mild throttle. The shifts do become more "solid" or "harsh" if you give it more throttle.
I replaced the throttle cable because I couldn't get the tbi to WOT with the pedal. I also replaced the tv cable with a new GM one because the lock appeared to be unable to hold in the correct position. I pulled the pan. The fluid was not burnt. There was a thin film of black stuff on the magnet, but nothing shiny. I verified that the TV lever was pushing the tv plunger flush with the tv bushing with the cable adjusted correctly at WOT. Drove it again and it acted the same. No difference whatsoever.
I pulled the valve body. The gaskets look brand new, i cant see any tears. I disassembled the VB and cleaned all the valves and the VB. No gunk or debris found. All the valves move smoothly with no binding. The tv plunger moves the TV valve smoothly, and strokes it to almost bottoming in the valve body (I dont know the name of the space in the vb). There was no debris in the case. The case and Valve body faces were deburred with a bastard file when I originally assembled the trans. I reassembled the vb to the case and again verified proper tv lever bottoming on the tv bushing with the tv cable adjusted correctly. Fluid level is perfect.
Pressures are as follows:
Idle: P=90, R=150, N=90, OD=90, D=90, 2=220, 1=220
1200rpm: P=110, R=180, N=110, OD=110, D=110, 2=220, 1=220
The pressure rises instantly with any throttle or with any manipulation (pulling) of the tv cable at the tbi.
If i disconnect the tv cable from the throttle arm at idle, the pressure is 80, I think my spring may be a touch long, but I would kill for late shifts at this point.
Drove it. No change.
Where do I go from here? Transgo tech support had nothing new to offer after going through their checklist.
My suspicion is that there is extra governor pressure for some reason. I think the governor is probably stuck. I am going to the garage to pull it now. If I pull the governor and there is nothing wrong I don't know what else to do.
Thanks for reading and sorry again for the long post.
Sorry for the long post.
I have a 1987 fullsize Blazer with a 700R4. It has the auxiliary valve body.
The trans was bad when I bought it. The converter was broken where the input shaft splines mesh, and the trans had 130k miles on it. I pulled it and rebuilt it with new clutches and steels, including the Raybestos 3-4 clutch pack. I put a newer valve body on it (a known working 1990 valve body). I also installed a Transgo 700 Jr. I replaced the input drum/input shaft. The pump had to be machined because of scoring. It has a new converter as well (obviously). This was the first 700R4 rebuild I have done.
When it first went back together it was great. The pressures were about the same as those recorded below. Good shift points, downshifts were appropriate, lockup working correctly, temps NEVER over 160 (measured at the pressure port above the manual linkage). I drove it around a bit, city and highway. I put about 150 miles on it and then....
One morning it started short shifting. 1-2-3-4 all by 20 mph. NO downshift with part throttle or WOT. Up in to 4th with the converter locked at 20-25 miles per hour and doing the lock-unlock-lock-unlock at mild throttle. The shifts do become more "solid" or "harsh" if you give it more throttle.
I replaced the throttle cable because I couldn't get the tbi to WOT with the pedal. I also replaced the tv cable with a new GM one because the lock appeared to be unable to hold in the correct position. I pulled the pan. The fluid was not burnt. There was a thin film of black stuff on the magnet, but nothing shiny. I verified that the TV lever was pushing the tv plunger flush with the tv bushing with the cable adjusted correctly at WOT. Drove it again and it acted the same. No difference whatsoever.
I pulled the valve body. The gaskets look brand new, i cant see any tears. I disassembled the VB and cleaned all the valves and the VB. No gunk or debris found. All the valves move smoothly with no binding. The tv plunger moves the TV valve smoothly, and strokes it to almost bottoming in the valve body (I dont know the name of the space in the vb). There was no debris in the case. The case and Valve body faces were deburred with a bastard file when I originally assembled the trans. I reassembled the vb to the case and again verified proper tv lever bottoming on the tv bushing with the tv cable adjusted correctly. Fluid level is perfect.
Pressures are as follows:
Idle: P=90, R=150, N=90, OD=90, D=90, 2=220, 1=220
1200rpm: P=110, R=180, N=110, OD=110, D=110, 2=220, 1=220
The pressure rises instantly with any throttle or with any manipulation (pulling) of the tv cable at the tbi.
If i disconnect the tv cable from the throttle arm at idle, the pressure is 80, I think my spring may be a touch long, but I would kill for late shifts at this point.
Drove it. No change.
Where do I go from here? Transgo tech support had nothing new to offer after going through their checklist.
My suspicion is that there is extra governor pressure for some reason. I think the governor is probably stuck. I am going to the garage to pull it now. If I pull the governor and there is nothing wrong I don't know what else to do.
Thanks for reading and sorry again for the long post.
