1996 with 124,000 miles update - oil pressure and transmission

[Scotty B]

Update on my project.

Removed the radiator and pressure washed. Installed 4K governor springs (thanks Big papa for suggestions) and removed the #6 plate. Installed a TST #8 and dialed back the AFC a little. No more overheating! But power is down a bit. I noticed an exhaust leak on the exhaust manifold on #1. I think the manifold is slightly warped. Needs a new one.

Had to have the transmission rebuilt. Metal fell out of the pan when I serviced. Lower reverse drum was badly fractured and the clutch pack looked like potato chips. I used Rob at Max Torque in Golden Co. He seems to be a 12 valve whisperer. He installed a billet DPC converter, mag Hytec deep pan, and various other billet parts. Shifts great and holds the current mild engine mods.

New issue.
Was towing my 5,000lb trailer to Laramie Wy up 287 (beautiful hilly drive north of Ft. Collins with some steep climbing sections). Truck had plenty power and held speeds with only 1100 degrees max on EGT's. Boost was steady at 22-25psi with the stock HX35. Would like to get another 50hp. Maybe injectors next?

Arriving into Laramie, I started to loose oil pressure. Upon acceleration, oil pressure gauge would drop to 0, then rapidly build back up as transmission shifted to overdrive and I let off the throttle. This freaked me out. After camping one night, we got safely home by not accelerating very hard. Was able to maintain 40psi at cruise - 70mph all the way home by not applying too much throttle at once. I checked the sending unit per the 1996 Dodge shop manual. All OK. Ordered a pressure gauge from Genos. Now waiting. I plan to install it in the spare port next to the turbo oil line off the top of the oil filter housing. What in the heck would cause this?

Notice the low oil pressure warning light did not illuminate. I think it comes on below 10psi?

Once home, I dropped the trailer and unloaded. Oil pressure would only slightly drop on hard acceleration w/o the trailer. Why would a load cause the oil pressure to drop during harder acceleration?

What possible damage to the motor could the previous owner have caused by running hard (toasting the transmission) on a #6 plate without gauges or any knowledge of how to drive this truck?

 

[Scotty B]

After taking my morning walk with the dog, I have a theory.

The PO overheated the motor so badly with the #6 plate it destroyed the oil viscosity. This resulted in badly wearing the main bearings. Now that I have a transmission that will hold the power here is what I am thinking.

Under a load, cylinder pressure is greatly increased. This puts a lot more stress on the mains, causing a complete leak out of oil, tanking the oil pressure. When I let off the throttle, oil pressure returns. The decrease in cylinder pressure allows the mains to seal back up, allowing oil pressure to rapidly return.

If I have to have the motor pulled and a new bottom end, what else should be done while out? I want this truck to last me the next 20 years or 300K miles, whichever comes first.

Thoughts?

 

[BigPapa]

I think you're over thinking it. I'd wait till you get the mechanical gauge and verify that it's actually losing pressure before coming to a conclusion.

 

[GAmes]

You can confirm or rule out excessive bearing wear with an oil analysis.

https://www.genosgarage.com/product/cc2525/oil-filters

 

[GrantP]

If it's bearing failure there should be plenty of glitter in the oil filter. You'll need to cut it open to take a look.

 

[Scotty B]

These are all helpful suggestions. I will wait for the autometer I ordered from Genos and compare to the in dash oil pressure unit. If it confirms, I will do the oil spectro analysis - which is a good idea - before going toward bottom end rebuild. Also trying to follow the Dodge service manual, but my symptoms are low oil pressure under load, not all the time. The main bearing check in this trouble shooting guide is what got me thinking about a main bearing failure - based on the PO's abuse of the motor.

 

[AnonEd]

I agree with testing that gauge. On a 1.6-liter gasoline four, which varied oil pressure by 120 psi depending on revs and oil temp, when my mains were tired (around 200K miles) cruising pressure by mechanical gauge -- 50-70 psi -- would drop momentarily by 3-5 psi when I matted the throttle and immediately start climbing with revs, but it never went to zero.

 

[Turbo Terry]

Test with gauge to be sure. Mine did similar and it was just the sensor. If you had zero pressure the motor would have blown up. I know that road. You would not have made it to Laramie let alone home

 

[Scotty B]

Thanks for the input. Installed the autometer from Genos. It is definitely the sensor. See install pictures.

Note the high tech white duct tape gauge installation. Have steering column gauge pod mount on back order from Genos.

Note the tan/orange stripe dimmer wire on the headlamp pull switch. I did a search on this wire and did not find a good image so I am posting this one in case anyone in the future searches for dimmer circuit for gauge installation.

 

[Cummins12V98]

That’s a great port to take an oil sample.

 

[Scotty B]

Good news! Oil sending unit fixed the problem. Now both gauges agree. Here are some installation notes.
1. Order the oil pressure removal deep thin walled socket!
2. Mine was very, very tight. Used a wiggler and 2 long 3/8's extensions with a 3/8 breaker to get loose.
3. Socket would not fit completely over the sending unit. I had to grind the edges because it was hitting the steering pump.
4. Make sure you order the correct sending unit. Round pin or flat. Mine was round.