700r4 no 4th gear after warmup

[RShrimp]

I just did a Transgo Reprogamming kit on my 700r4. The trans was in good shape and worked in all gears (no Lockup but that's another story) It was, however weak slow shifts. Fluid was clean and just a little gray goo on the magnet. I followed the instructions to a T, watched several videos ect. I will say I will never do another on in the truck as it just makes too big a mess. I now shifts good and hard 1 to 2 , 2 to 3, and 3 to 4 whicj was exactly what I was after. Oh, Stock TBI 350 for now. When it's cold it works perfectly
The problem is after warmup of 10-15 miles it quits going into 4th. If you leave the lever in OD it will kind of fall out of 3rd but never go into 4th. If you let off the gas the engine goes all the way to idle and when you step on it it free revs up to the point where the revs match and then goes. If you put the lever in D or 3rd it does not do this and it does some engine braking. Sometimes I can get it go into 4th by manual shifting it from a stop. Once in it will stay in until I slow down or hit the throttle hard (as expected)

The one part of the kit I did not do is the Servo ( I did not mess with it at all) 3 inch exhaust runs right next to it and I was afraid I would never get it back in and the band adjusted correctly so I just left it alone.
I installed a new TV cable and adjusted it by simply fully opening the throttle.

 

[Drunkcanuk]

Check out the sticky in the transmission section, 2nd one down. @NickTransmissions did an excellent write up on how to set the cable properly with pressure readings.

Also...how is the fluid level?
Did you check it when it was hot and up to temperature?

 

[NickTransmissions]

I just did a Transgo Reprogamming kit on my 700r4. The trans was in good shape and worked in all gears (no Lockup but that's another story) It was, however weak slow shifts. Fluid was clean and just a little gray goo on the magnet. I followed the instructions to a T, watched several videos ect. I will say I will never do another on in the truck as it just makes too big a mess. I now shifts good and hard 1 to 2 , 2 to 3, and 3 to 4 whicj was exactly what I was after. Oh, Stock TBI 350 for now. When it's cold it works perfectly
The problem is after warmup of 10-15 miles it quits going into 4th. If you leave the lever in OD it will kind of fall out of 3rd but never go into 4th. If you let off the gas the engine goes all the way to idle and when you step on it it free revs up to the point where the revs match and then goes. If you put the lever in D or 3rd it does not do this and it does some engine braking. Sometimes I can get it go into 4th by manual shifting it from a stop. Once in it will stay in until I slow down or hit the throttle hard (as expected)

The one part of the kit I did not do is the Servo ( I did not mess with it at all) 3 inch exhaust runs right next to it and I was afraid I would never get it back in and the band adjusted correctly so I just left it alone.
I installed a new TV cable and adjusted it by simply fully opening the throttle.

Sounds like you didn't follow a couple essential steps: TV Cable adjustment valiation via pressure testing and servo travel check to ensure your band clearance was/is appropriate...Drop the pan then air-check the 4th gear apply via the little hole on the pan rail right under the servo...Watch the band grab the drum. If it's weak, pull the cover off and install a viton rubber seal there then reinstall (your servo cover may be a bit worn and the teflon sealing ring isn't fully able to seal). Next, check your TV Plunger-actuator arm pre-load...You should have that arm putting a small amount of pressure on the plunger such that as soon as you tap that gas, the plunger gets pushed in and you get immediate TV boost pressure rise. If that's not happening, that will cause your problems and then some.

Next, fix your TCC lock up...you are heat-soaking your transmission by driving around with no L/U functionality.

let us know your pressure readings and what you found when you inspected/air checked the servo and TV actuator arm/plunger relationship.

 

[Erik the Awful]

Don't drive it until you follow Nick's advice. If your TV cable is too loose you will burn up your transmission.

 

[RShrimp]

Went to HF and bought a gauge yesterday evening. I did fix the TCC by installing a 4th only vacuum controlled lockup harness. (All the internal wiring and the lockup solenoid was missing) For the first 10 miles the trans works flawlessly. All for shifts are crisp and firm. Lockup works perfect above 13 inches of vacuum in 4th gear. I could probably drive it 100 miles in 4th gear locked up if I didnt ever slow down. Once it is fully warmed up the next time I stop I get no 4th gear but 1,2 and 2,3 shift is still firm and crisp. It will "drop out of 3rd: but never goes into 4th. I did not mess with the 2-4 Servo and it worked fine before. I need to do the test hot which I did because there is no point in testing it when its working. I could not get it to 2000RPM as it spins the tires at around 1500. I disconnected the TV for the first test and pulled it all the out and clamped it for the second
Results from Hot test reveal very low line pressure readings when hot. I installed a .422 Boost valve with the shift kit as the one that was in the trans was very small and according to instructions required replacement.
Minimum TV
Park 60PSI @ 1000rpm
Reverse 60psi @ 1000 and 90psi @1500
Low 65psi @1000 and 90 at 1500
TV FULL PRESSURE
Park 75psi
Reverse 80@1000 and 90 @ 1500
Low 65 @1000 and 90 @1500.

 

[Erik the Awful]

Oof. Your pressure readings are lower than mine were. On Nick's recommendation I bought a new plunger and sleeve and it brought my pressures back up.

 

[NickTransmissions]

Went to HF and bought a gauge yesterday evening. I did fix the TCC by installing a 4th only vacuum controlled lockup harness. (All the internal wiring and the lockup solenoid was missing) For the first 10 miles the trans works flawlessly. All for shifts are crisp and firm. Lockup works perfect above 13 inches of vacuum in 4th gear. I could probably drive it 100 miles in 4th gear locked up if I didnt ever slow down. Once it is fully warmed up the next time I stop I get no 4th gear but 1,2 and 2,3 shift is still firm and crisp. It will "drop out of 3rd: but never goes into 4th. I did not mess with the 2-4 Servo and it worked fine before. I need to do the test hot which I did because there is no point in testing it when its working. I could not get it to 2000RPM as it spins the tires at around 1500. I disconnected the TV for the first test and pulled it all the out and clamped it for the second
Results from Hot test reveal very low line pressure readings when hot. I installed a .422 Boost valve with the shift kit as the one that was in the trans was very small and according to instructions required replacement.
Minimum TV
Park 60PSI @ 1000rpm
Reverse 60psi @ 1000 and 90psi @1500
Low 65psi @1000 and 90 at 1500
TV FULL PRESSURE
Park 75psi
Reverse 80@1000 and 90 @ 1500
Low 65 @1000 and 90 @1500.

Something's wrong...Either your geometry, adjustment or worn components inside the transmission such as TV boost valve, plunger/sleeve, pump pressure regulator valve, boost valve and/or excessive clearance in the pump's rotor and slide to deck surfaces. First things I'd do is verify your geometry; you can't just be 'close' or 'sort of correct' with the geometry, it has to be spot-on. Once confirmed, readjust the cable until either line pressure rise is restored or you have ruled out your geometry and cable adjustment as the culprits. Note - if your cable is old, replace it.

Full TV pressures should be 130-160 PSI in P, N, D, D3 and Reverse should be 90-120 PSI at min TV, 150-200 PSI at full TV.

Lastly, if you only have a .422 boost valve in the pump, upgrade to a .472 boost valve at minimum...No 700R4 leaves my shop with a .422 boost valve, I feel they are inadequate, especially given more and more folks w/700s are using them in resto mod swaps with engines making more than factory power.

 

[RShrimp]

I am going to wait for Nick's reply but is that the parts that go in the same hole as the boost valve? Got PN#s?

 

[NickTransmissions]

I am going to wait for Nick's reply but is that the parts that go in the same hole as the boost valve? Got PN#s?

Please quote my post or mention me as I just happen to see this reply as it was at the top of the 'Transmissions' sub-forum. Yep, the boost and reverse boost goes into the pump which can be accessed via the snap ring once the pan and filter is out of the way...I'd replace them both (.472 boost and new reverse boost valve/sleeve).

 

[RShrimp]

Geometry is factory stock TBI so that not likely the issue. TV cable is new. Engine has the factory 210HP so I dont think the .422 is causing the issue but if I take it apart again I will just go ahead and put the .500 in it. I think I am going to circle back to the boost valve in the pump. It all worked fine before the shift kit install. I replaced the boost valve and used springs from the shift kit. It almost has to my mess up. It was difficult to get the boost valve and assembly back in with the trans in the car. It went in without a lot of force but I had to fiddle with it a bunch to get it to push in and get the snap ring in there working upside down.

Question: It looks like the pump will only make 90psi no matter what I do with RPM or TV. Could the boost valve be laying in the pan? Maybe I didnt get the snap ring seated although I triple checked it. Is there a way to get the order of things correct but still install it wrong? Just seems strange that the entire thing works perfectly until it gets hot.

I think I will put the gauge on it again cold and see where we are when it works.