Torque Converter Blackmagic "is it stalling me out"

[MonkeyMadness]

Okay so I'm gonna ask a question that sounds dumb at least to me. I'm having a hard time wrapping my head around the issue.

The setup: So I have what I consider a mild built motor in my D100. 318/396 stroker, speedmaster heads, port matched Edelbrock single plane intake, Holley Sniper 2, comp cams mild cam 20-222, and long tube header and full custom exhaust. The motor runs really well. Its backed by a rebuilt 46RH with a stock replacement converter and it had a 8.25" & 3.23 gear with 20x8 wheels 31" tall... With all this the truck was strong but the gear felt lazy off the line, so I swapped out the 3.23 for a 3.91. YES! now this truck runs exactly how I've wanted for a while. Good punch of the line power band in the right spot for each gear cruising at round 2500rpm at highway speeds.

The Problem: Coming up to a light if I slow down to fast I can feel the motor struggle and then it stalls.....?WTF? If I slow early and I allow the trans to down shift as on its own as I pull up the motor still struggles a but will recover and idle. If I roll up at normal speed and shift into neutral before stopping no issue, unless I'm really going fast. My first thought was my lockup converter was still engaged and causing the issue so I disconnected the lockup and still have the issue... also I noticed when starting the motor if I toss too fast into gear forward or reverse it will also stall... I'm at a loss... "Also I have manual brakes so its not pulling a vacuum"

The Question: Could the stock stall converter be stalling out my motor? -This sounds so dumb to me-

 

[Professor Fate]

I may be way off base here, it's been a while since I wired up a lock up; so forgive me if I'm full of hooey- and I don't have a relevant FSM handy to double check...
But from what I think I remember about the H transmissions is that the electrical connections are to bypass the convertor lockup and OD engagement (tow/haul switch), so you need to supply 12v to it in order to keep it from locking up- disconnecting it would simply allow it to continue to engage and disengage on it's own. So, you may not have eliminated the TC lock up from the equation by disconnecting it. Try supplying 12v to the trans connection and see if that prevents lockup.
Then again, I could have this totally bass-ackward and early senility is setting in...

 

[Oldmanmopar]

Install a return filter after the mechanical pump . Or a return regulator after the carb with and electric pump.

 

[TT5.9mag]

I’m just going to throw this out there as a possibility, not related to transmission at all. With a carb, usually that symptom is due to float level adjustments. Too high will stall on decel or stopping. How is decel fuel handled in your sniper 2 setup?

 

[Demonx2]

Does the Sniper-2 have a DFCO (Decel Fuel Cut-Off) feature like all OEM fuel control systems do? If it does, I would think the RPM or speed to re-enable fuel would be a calibration value that you could adjust.

What you are describing sounds like DFCO that is not re-enabling in time (i.e. turning the injector(s) back on) and simply stalling out the engine. That being said, OEM systems also have the torque converter clutch ("lockup") and other variables to work with to get the coast to a stop engine control right. I am totally unfamiliar with these aftermarket systems as I worked on/with the OEM stuff for too many years!

 

[TT5.9mag]

I’m guessing the sniper 2 has no auto trans control functionality at all and it would be useless on a 46rh anyway. Also, @MonkeyMadness has already disabled clutch lock up and overdrive as a test.

 

[Syleng1]

Have you tried before coming to a stop throwing it in neutral and see what it does? This would eliminate fuel or ignition issues. And if the converter is staying locked you can test this by putting your truck up against something that will not move and put it in gear. If you back off the throttle and the truck stalls then your converter is staying locked (wired correctly- the 12vdc solenoid dumps od pressure to disengage lock up- no power and it locks up….. what controlling your lock up just a manual switch?)

 

[TT5.9mag]

If I roll up at normal speed and shift into neutral before stopping no issue,

Have you tried before coming to a stop throwing it in neutral and see what it does? This would eliminate fuel or ignition issues. And if the converter is staying locked you can test this by putting your truck up against something that will not move and put it in gear. If you back off the throttle and the truck stalls then your converter is staying locked (wired correctly- the 12vdc solenoid dumps od pressure to disengage lock up- no power and it locks up….. what controlling your lock up just a manual switch?)

Did you read the original post? See his quote above.

 

[Syleng1]

Did you read the original post? See his quote above.

Thanks- I must had not seen that.
So if he is stalling stoping then typically the converter is staying locked. Or distributor weights could be sticking or fuel issues. I still have not seen confirmation that it is wired properly.

 

[TT5.9mag]

Install a return filter after the mechanical pump . Or a return regulator after the carb with and electric pump.

It’s fuel injected

 

[TT5.9mag]

On a stock RAM with a 46RH, how do they tie the brake switch in to the converter lock up control? I know how it’s done on a 46RE but I am unfamiliar with the RH. I’d get a copy of a service/repair manual for a truck with that trans and start looking.

 

[Oldmanmopar]

It’s fuel injected

Then I would say you need a looser torque converter . The engagement is not letting it go to idle if you leave off to fast right before stopping. sounds like the cam is to large for the stall speed.

 

[MonkeyMadness]

I'll check into the efi cut off for decel DFCO, as well as an "auto" setting. I did have the idle set at 650rpm while it had the 3.23 gear. And after the 3.91 swapand the initial stall I jumped the idle up to 700 and it now at 750 without a change.

Then I would say you need a looser torque converter . The engagement is not letting it go to idle if you leave off to fast right before stopping. sounds like the cam is to large for the stall speed.

See this is what I'm looking for. "I didn't know" this was a thing?

 

[TT5.9mag]

I'll check into the efi cut off for decel DFCO, as well as an "auto" setting. I did have the idle set at 650rpm while it had the 3.23 gear. And after the 3.91 swapand the initial stall I jumped the idle up to 700 and it now at 750 without a change.


See this is what I'm looking for. "I didn't know" this was a thing?

It’s not. It’s all about the lock up clutch and when it dis engages. You can have a 5000 stall converter and if it stays locked it will drag the engine down.

 

[Syleng1]

On a stock RAM with a 46RH, how do they tie the brake switch in to the converter lock up control? I know how it’s done on a 46RE but I am unfamiliar with the RH. I’d get a copy of a service/repair manual for a truck with that trans and start looking.

The computer controls that portion of the program. With a relay, you can disconnect easy enough but you do know that lock up should only come on at like 3.rd gear and over 50mph right?

 

[TT5.9mag]

Now if the converter is not a lock up and has mechanical issues internally, then the same thing can happen. Once again, stall speed has zero to do with it.

 

[TT5.9mag]

The computer controls that portion of the program. With a relay, you can disconnect easy enough but you do know that lock up should only come on at like 3.rd gear and over 50mph right?

Yes I know the stock routine. I just am not aware of how the ecu disengages the lock up at the braking point and how the aftermarket “kits” for an RH simulate it.

 

[TT5.9mag]

@Bobzilla are you familiar with how the ecu disengages lock up on a 46RH when braking?

 

[MonkeyMadness]

I'm using the PATC O/D kit for the trans and it uses line pressure to engage or disengage the o/d and lockup, and a vacuum switch to read throttle position.

 

[TT5.9mag]

I'm using the PATC O/D kit for the trans and it uses line pressure to engage or disengage the o/d and lockup, and a vacuum switch to read throttle position.

View attachment 1716444048

I figured you were likely using a PATC kit. I would absolutely wire in a relay, controlled by the brake switch to disengage lock up at any time the brakes are hit. That’s a safety issue and even if it isn’t your problem, needs to exist.

 

[autopar3000]

Yes I know the stock routine. I just am not aware of how the ecu disengages the lock up at the braking point and how the aftermarket “kits” for an RH simulate it.

It's based on throttle position. As soon as you let off the throttle the PCM will tell the converter to unlock.

 

[TT5.9mag]

It's based on throttle position. As soon as you let off the throttle the PCM will tell the converter to unlock.

So the ECU controls the ground side of a relay somewhere?

 

[autopar3000]

So the ECU controls the ground side of a relay somewhere?

Surprisingly, in the OBD1 trucks there is no relay. The PCM just sends the ground signal itself. I can't say for sure without checking the FSM, but I think they added a relay in the OBD2 trucks. My engine and trans combo is from 1994 so that's where my expertise is.

 

[autopar3000]

I'm not sure if the tight converter is your issue, but I can tell you I have a ~2500 stall torque converter behind a 46rh, and it's fantastic. Running a 3.73 gear with a 26 inch tire, so probably pretty close to your RPM range.
I can be cruising along at 1500 rpm in 4th gear (45 mph) and when I get on the throttle the engine will flare up 1200+ rpms for acceleration. Get out of the throttle and it settles back, and never leave 4th gear.

 

[TT5.9mag]

Surprisingly, in the OBD1 trucks there is no relay. The PCM just sends the ground signal itself. I can't say for sure without checking the FSM, but I think they added a relay in the OBD2 trucks. My engine and trans combo is from 1994 so that's where my expertise is.

Thank you. I can’t check the FSM because i don’t have a copy for an RH controlled truck. If you do can you verify please?