No power in reverse

[Zamboni]

So the issue I'm having is i have no power in reverse, not transmission problem power but my truck will not push my 5th wheel trailer in reverse up an incline, just black smoke. So ever since i changed to an HX35 turbo and a lower stall torque converter this has been an issue. My thinking on this problem is the lower stall converter is not allowing the engine to increase in rpm to get any boost from the turbo. So question is, will my old hy35 spool better with this setup or would a stock or higher stall converter be a better option or am i just missing something? 

[Dieselfuture]

I don't think it's your turbo at all, you can always check for both clicks to be sure but you really don't need boost backing up a trailer. Sounds like there may be an issue with your transmission.

[IBMobile]

I have a HX35 turbo and an 800 RPM stall convertor with no problems backing an 8K 5th wheel up a steep driveway into my backyard.   

The rear transmission band may be slipping.   Put the transmission in manual 1st and accelerate checking for slippage.  Only reverse and manual 1st use this band.

[Zamboni]

I use manual first all the time, there is no slippage. I pull a 12k pound trailer and start out in manual first and reach 30+ lbs of boost with no issues. It just won't push a trailer up a hill in reverse. I don't get it. I was ready to give up on this truck last year and decided to install the adrenaline now I'm second guessing that decision. 

[ddmk6]

I just put mine in 4 low.  I had an ATS transmission built before I started adding more power.  It's rock solid, just no low end.

[Zamboni]

2wd

[Haggar]

When in reverse trying to back up the weight, does the engine freely spool up or does it try to stall?

 

If the engine rpm increase with no gain in speed, the clutch is slipping or the torque converter is not converting.    If you stall you don't have enough torque to perform the maneuver. 

 

HTH
Hag

 

 

[Mopar1973Man]

For sure not the turbo. I would look at the transmission and torque converter.

[Zamboni]

In reverse under load rpms will not go above about 1200 and lots of black smoke. Rpm does not increase and engine does not stall. It just bogs down. Trans has a couple thousand miles on it with a single billet DPC converter, has no issues other than no reverse power with a load. Go just fine in reverse unloaded. Have had problem with 3 different trailer of various weights. 

Not sure where to go from here. 

[Tractorman]

29 minutes ago, Zamboni said:

In reverse under load rpms will not go above about 1200 and lots of black smoke. Rpm does not increase

 

16 hours ago, Zamboni said:

I use manual first all the time, there is no slippage. I pull a 12k pound trailer and start out in manual first and reach 30+ lbs of boost with no issues. It just won't push a trailer up a hill in reverse.

 

First gear ratio is 2.45:1, reverse gear is 2.21:1.  Reverse gear provides less torque to the rear wheels.  What is your rear axle ratio?  I am guessing 3.54:1.  

 

23 hours ago, Zamboni said:

So ever since i changed to an HX35 turbo and a lower stall torque converter this has been an issue. My thinking on this problem is the lower stall converter is not allowing the engine to increase in rpm to get any boost from the turbo.

 

I think you may be correct about this - especially if your rear axle ratio is 3.54:1.  I also think that the HX35 turbo would be more suited for the low stall converter than the HY35 turbo.  The HX35 should spool earlier in rpm's under load so it would be a better match with a low stall speed torque converter.  

 

- John

[Zamboni]

So i have the hx installed now. This problem seemed to evolve when i switched from the hy i think. I was thinkin hy would spool better due to smaller housing. May be something in trans but don't understand why just with weight. 

[Dieselfuture]

Could it be map sensor telling ecm something goofy, can you see life data.

[Zamboni]

I can hook up my scanner and check. That would make sense. Not sure why in reverse only but it is worth a try. 

[Tractorman]

What is the read axle gear ratio?  It is not listed in your signature.  It matters.

 

Clearfield, Utah is above 4,000 ft elevation. - much lower air density than at sea level.  Most turbochargers are out of their efficiency zones at low engine rpm, especially at higher elevations.  Things that will negatively affect getting a turbocharger to spool up under a heavy load.:

 

*  3.54:1 axle ratio vs. 4.10:1 axle ratio

*  low stall torque converter

*  4,000 ft elevation

*  2.21 reverse gear ratio vs 2.45 1st gear ratio

 

You may not be experiencing the problem in first gear because you have more torque to the ground just because of the first gear ratio.  This equates to less load on the engine.

 

The combination of all of these things could easily put the engine into a condition that the turbocharger cannot gather enough air for efficient combustion when trying to move a heavy load from idle, consequently, lots of black smoke.  I am not saying that there is not a transmission problem or another problem;  I am just trying to show what is working against you, so that you can take it into consideration.

 

1 hour ago, Zamboni said:

May be something in trans but don't understand why just with weight. 

 

If there is less load on the engine (less weight), there could  be sufficient ambient air pressure (available oxygen) combined with a little boost to get the engine above 1200 rpm, which will get the turbo closer to its efficiency zone.  Once that happens, the power comes on and the smoke clears.

 

- John

 

Edited May 4, 2021 by Tractorman

[Zamboni]

It is the 3:54(55) rear end. We are about 4700ft. I think i will install my hy turbo and see if it makes a difference, that is a free and easy swap and that seems to be when the problem started. I only changed it to try and lower egts but no with the adrenaline they are under control. 

[Tractorman]

After doing a bit more reading, the HY35 turbo may spool better in that dead zone just because it has a smaller exhaust housing.  However, exhaust gas temperatures may run hotter under higher rpm loads than the HX35  I guess you will find out when you make the exchange.

 

- John

[Dynamic]

What is the stall speed of your DPC converter? Many people get carried away with lowering their stall speed. A little tighter than stock is all you want, and at altitude a good case could be made for a stock stall converter in your application. Also, Tractorman is exactly right. The reverse gear ratio of a 47RE/48RE is very tall - somewhere between 1st gear and 2nd gear when compared to the forward ratios.

[Zamboni]

Im not sure on the stall. It came with a kit i bought, all the invoice says is dpc drm1 low stall converter. This problem may have started after converter install, i changed the turbo after 1st trip with new trans and noticed problem when i tried to get my 5th wheel back in my yard which is a slight incline.