Stutter in reverse after Transgo and Sonnax Upgrade

[DBarfield]

I have a 2004. 5 3500 48RE with 77,000 miles that I just did a Transgo shift kit with several of the Sonnax Valve upgrades that are discussed on TDR. 3 to 4th is very crisp but 1-2 and 2-3 are almost mushy. My issue is with reverse where there is a stutter and I have heard a metal type grind initially and it takes 3 to 4 seconds before there seems to be full power to reverse. Both bands were adjusted per FSM. I have not driven the truck with a load yet but unloaded it is fine.



Interestingly, I ended up with an extra check ball (1/4" Steel) after everything went back together. I have looked through the FSM and ATSG transmission manual and double checked the 7 check valves that the FSM called for. I did not drill any of the valve body or plates instead using the Sonnax valves. I tried to use the OEM spring etc. when the forums said to for not creating a hard shift.



The only issue that I had before the upgrade was during initial launch, forward or reverse, in that it took a very heavy foot on the pedal to get a heavy load (14,000 pound) started.



The parts that I used were,

Transgo shift kit

GM Pressure Control Upgrade

53397A Governor Pressure Sensor

Sonnax 22771A-02K Pressure Regulator valve

Sonnax 22771-09 Manual valve

Sonnax 22771A-01 4 spool valve

Billet Strut and Anchor

Billet Accumulator piston

Removed the drainback valve in coolant line

Gauges in pan and hot line - staying less than 150d unloaded

Amsoil to top off system, about 2 gallons.



First time posting but have enjoyed TDR since 2006. Any thoughts would be appreciated.



David

 

[cerberusiam]

Offhand, it sounds like a possible problem with the rear servo. They have a problem jamming in the bore.



Run your pressure tests and see what that tells you is the best way to start. Something may be obvious from there.



How does manual 1st work?

 

[DBarfield]

Going forward seems to be fine. I will need to get some gauges.

David.

 

[DBarfield]

I finally was able to test the pressures. 160 psi on the rear servo port in Reverse. FSM seems to point to rear band out of adjustment.



First gear seems to be okay. It does not seem to slip like reverse does but I have not had a load on it to stay in first.



I need to pull a trailer tonight so it appears I need to drop the pan and check the rear band adjustment. The rear servo was mentioned as sticking, is there something that I can look at while the pan is off?



I really do not want to drop the valve body today but will consider it if necessary.



David.

 

[cerberusiam]

The pressure is low on the rear servo, that sprobably causing the chatter because reverse is an abnormal highly leveraged condition and low pressure will cause skip.



You can try adjusting the band but my guess is the seals are blown on the rear servo or you have another leak down on the circuit.



You have to disassemble the trans to ge tthe servo out and check it. Pretty hard to tell in th etrans if it is bad. IIRC, the apply pressures on the rear servo should be 300 psi or so in reverse.



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[DBarfield]

I have dropped the pan and I found the rear servo band adjustment was loose. I reset the adjustment and LOCKED the adjustment screw this time. Reverse seems to be at least back to where it was before I dropped the valve body.



I had the gauge in the rear servo port and it read 160 at Idle. Holding the brake and revving, the pressure raised to 230 to 240 range. I will know in a couple of days if I still have an issue.



Thanks for your help.

David.

 

[cerberusiam]

Yeah, it was loose and slipping.



Since you have an 04. 5 with a TV cable all you need to do is advance the TV cable to see what the max is, you don't have to rev the engine.



Your numbers look better and if you max the TV lever at 1600 rpms it should go over 300 psi with the shift kit in it.