New rebuild with hd2 kit 2001 with no internal mods

Runs and shifts proprrly forward all gears . In Low - first gear accelerate and coast engine brake holds fine to the band engagement.

Shift into reverse line pressure shows 0 - 9 psi. Rev engine may raise it to 20-40 max

It is in reverse as the sljght backward draw can be felt and if a bounce stop is made immediately to reverse it may move slightly in reverse.

Have not tried to unplug the connector to force manual mode yet

Hd2 kit only plate and boost valve and its springs used - and intermediate snap ring

All forward shifts respond with aggressive throttle to raising line pressure

Once warn holds 35 psi in park and 45-50 in gear at a stop light. I plan to turn up the EPC solenoid slightly when I drop the pan to 50-70 at idle in park

Does anyone know how the manifold pressure and external prndl switch plays into a command to provide reverse gear pressure??

Have ttransducer 0-300 permanently installed port with electronic readout

 

Fact with presure that low you have a BIG BIG leak in REV. ARE you sure you are feeling 1st gear engine braking in M1 as last time I saw the presure drop that low in REV the center had broken out of the low servo and yes was on a new build , Reason I started using the billet low/rev in these. Wherever your line is going is where reverse is .
Havent used a TG kit in many years in one of these. But cant think of a mess up with that which could get you here.

 

Another possible missing low/rev check ball in VB

 

Thanks for the prompt response.

I aassume the checkball referred to is the ond this kit repairs? https://www.sonnax.com/parts/4715-7-...checkball-seat

I did not check that in the valve body

It was a bone yard core that had been rebuilt and I found mix-matched direct and forward steels, a torn intermediate lip seal, hard fourth piston apply seals that one could blow past with breath,, forward drum chewed up input shaft riding surface, and 71 thousandths intermediate frictions where 80 's should be. (it is a 2001 tranny)

I ffixed all that and otherwise the tranny was a new rebuild with pink fluid and new frictions measuring to new spec - except the intermediates clearly slipping down to 68 thousandths

The hd2 kit called for 7 checkballs and I am certain they all went in, but this low reverse check ball apparently goes inside the valve body

I wwill get some things ordered up for the pan drop

Thanks I will report back
I am pretty sure I felt good engine braking in low, but will check again tomorrow

 

I verified engine braking in low.

When II unplugged the transmission connector it threw P0753, 758 and 1860 but no P0748 which is the EPC solenoid code it "should" have thrown

This is odd to me

I did put a new transmission wiring harness in the rebuild.

Is there a way to test using a new pigtail connector plugged into the transmission???

 

Do yo have reverse with harness unplugged? No electrical situation will prevent reverse or cause presure to go that low, IMO you are chasing your tail doing anything other than 1st pull VB and check that LOW/REV BALL in it .Then I would air check the DIRECT ( YES UNLES DUAL FED YOU CAN HAVE GOOOD 3RD WHILE HAVING NO REV AND MASSIVE LEAK VIA A BROKEN RING ON CENTER SUPPORT) Pull rev servo inspect and check clearance to band. reality no rev and presure loss, your issue has to be in one of these places. Reverse will work fine normally with harness unpluged, If it dont work then you absolutly have a massive internal VB-SERVO-DIRECT CLUTCH LEAK

 

Thanks for the prompt response.

Yes uunplugged connector rear wheels off the ground they turn in reverse.
I rremember removing that check ball in the valve body to change the o ring, and I am sure I reassembled it with the checkball.

If by "broken ring" on the center support you are referring to the intermediate clutch pack snap ring, that is a new wider Chrysler style A518 ring, If you are not referring to that then what "broken ring" are you referring to???

I asked about the "MLP" PRNDL switch (and manifold pressure swith on valve body) because I put a new transmission wiring harness in the rebuild and it had an EPC solenoid plug that could go on either way and the wire colors did not match the original.

Because unplugged, the ECM did not throw the P0748 code like it lost communication to the EPC Solenoid I am puzzled . But it threw the P0753, 758 and 1860 (missing) but no P0748.

Remember this has a hd2 trople valve body plate which modifies and uses the reverse circuit to dual feed the direct clutch.

I air checked the three circuits at the center support feeds and while assembly lube may have masked a problem, there were no leaks. How can low hold tight to the band if the servo is leaking???

I aagree I should pull the srrvo, inspect and extend the pin and set throw / apply clearance.

The PPRNDL switch was out of adjustment or faulty because I could slowly apply pressure towards park but just before the rooster head engaged "park" the line pressure would go to 150psi, but by that time the manual valve was out of the reverse fluid circuit.

I have ordered the servo pin extender and reseal kit as well as a new gm pin just to be sure.
I may order the sonnax heavy duty piston also.

But tthe manifold pressure switch is new as well as the harnesz, and could be faulty - even "new" - I have seen that case.

I don't have a scantool to temporarily turn up line pressure to check the EPC solenoid to see if the ECM even has control to it.

That is why I am trying to understand the relationships of the EPC solenoid, the manifold pressure and PRNDL switch to affecting the reverse gear line pressure

I can rev the engine and line pressure will bounce to 330 psi momentarily - but the transducer is only rated 0-300 so that is maxed out.

Driving under agressive acceleration line pressure will go to 240 to 290 and cruise around 150

So rright now before I drop the pan, if the EPC solenoid or cable is bad because the ECM cannot control it, I need to have that on hand too or if the vehicle wiring harness transmission connector is bad.

Those HD2 valve body separator plates are known to cross leak and right now I suspect the plate more than anything.

I have another new hd2 kit that shipped without the plate assembled and I may assemble those plates with hydraulic thread locker or jb-weld thinly applied to stop the cross leaking before installing it.

So tthat why I am asking if you know the relationships of the EPC solenoid, the manifold pressure and PRNDL switch to affecting the reverse gear line pressure

 

The PCM does raise line when it sees reverse via the MPS but regardless of that you sould have reverse and no electrical condition could drop the presure to the low level you are talking and no electrical condition can cause a NO REV scenario . In the manifoild sensor the only posssible leak would be the oring physically missing.
With rings I mean the ones on the center support to direct clutch .
Also note I did have a one of situation many years ago but not quiet like yours. With it I had a normal rev engagement at idle even normal motion at light throttle but little more rev would just quit , The direct drum was cracked and would separate and dump oil when presure went up, But thats not you symptom. I am however comcerned you just said you could kick up to over 300 psi in drive . to me that is way high to me 220 230 is max in D SOME WOULD ARGUE IT SHOULD BE LESS .
Also if you have the TG and you have the presure release on VB they send , This is also a potential trouble point I would eliminate as it could be popping off in reverse dumping the oil. I never use those and suggest you block the hole and elminate if installled .
I still say MASSIVE INTERNAL LEAK VB-CENTER SUPPORT RINGS- TRANSGO PRESURE RELIEF -LOW REV SERVO . One of those is your problem based on the presure drop you mentioned. I would not chase any electrical gremilins that may exist till I had a normal rev not just on lift but on ground pulling with haness unplugged.
Back to EPC though I DO NOT THINK IT IS CAUSING YOUR REV ISSUE unless the line is going high enough to popofff the TRANSGO RELEIF SPRING VALVE is your issue , If indeed you are getting 300 plus at WOT I would change it, Direction of plug in does not matter BTW your drive presure should look like 50 to 80 at idle I like 60 to 80 psi and 200 to 230 WOT max, Some would argue that is even to high.
But I stand with your NO REV is one of the above I mention as a massive leak

 

No Transgo cone relief valve. I did not drill the valve body for it.

Won't do over 300 psi in drive, only a rev of the engine in park. Runs 270 maxon hard acceleration.

Found this circuit diagram and if check ball seven can fall out of the case, then it is missing

I will need to drop the VB to see


Reusable pan gasket so I will turn up the EPC solenoid first

I will deal with no reverse until the sonnax heavy duty low / reverse piston arrives and I verify electrically the EPC solenoid is talking to the ECM

 

Boost valve in pump pushed the OEM snap ring out and was riding partially out until finally came out completely with a total loss of line pressure

At least I was parked.

Used the more beefy snap from the hd2 kit and now I have reverse

 

Well that would explain the presure and massive leak in reverse as the rev part of the boost valve is fed directly with rev oil. I did consider this but thought but he has good really actualy overly high FWD presure, It must have landed just right somehow , I have seen them come completely out and lose all presure. Good you are fixed , Unlikley scenario but hey they happen too. I have seen many odd and strange things with trans in my years.

 

Unfortunately not fixed.

I had reverse, but lost all line rise in forward so it would not move.

I was going to wait on a new filter to see if it was a suction restriction I noticed when putting boost valve back in.

I could not blow with my breath back through the filter.

I ordered fluid, filter, and host of other thing from Amazon to deliver to a locker one mile away.

Long sstory short, it was clogged, but I swiched to a Sonnax 34200-01k boost valve and made the mistake of turning up the EPC solenoid a little bit of an eighth turn

I thought the 34200-01k was a stock valve with o-ring seals.

Apparently is the same as the Sonnax LB-1 which raises pressure when used with a certain spring

I found that later and used the springs that came with the HD2 kit

This combination resulted inreally high line pressure near and over 330 psi, at idle, but remember the transducer os only 0-300 psi which means it was likely higher.

However now no reverse again.

Driving it would be under 250 so I figured the next morning I would put the HD2 kit boost valve and its springs back in.

The next morning on start the line pressure went over 335, and then all forward line rise and won't move, and it goes to 60 at idle but goes to zero in either gear.

Then I found this https://ls1tech.com/forums/automatic...rse-boost.html and there was no resolution to that thread post but it appears the valve can block reverse boost and without the proper springs give the results I have been trapped in.

So I can only hope it has not blown seals or piston seals

 

EPILOUGE. In the end, the feverse servo pistion bore in thecase was wallowed to one side preventing full travel possible.

This resulted in once the band wore enough reverse would not hold, and eventually neither would forward.

The boost valve coming out twice wore the budhing to permanrnt low line pressure

Of ccourse out it came, the old tranny had mrtal to metal frictions on three dufect clhgches. New firwards, directs and intermediate with wide snap ting and it goes agajn fineI wwill into repairing the old case later