[bmj26]

hey guys
1996 f350 7.3 powerstroke

not sure what the issue is here.. when i'm driving and i reach 3rd gear (roughly 40mph) the rpms go from about 2700 right down to anywhere from 1000-1400 when the truck shifts. it is an automatic. the engine is then bogged out and the whole truck sort of does some type of shake. the only way to get power back is to let it down shift or to give it copious amounts of throttle. the turbo does not spool at all when this issue occurs (i have a gauge). the weird thing is, sometimes it will not do the shake and will provide a normal amount of power. not sure if it helps but there's about 285k on the engine.

i'm not sure if this issue is also related, but when i shift from drive to either neutral, reverse or park the rpms will dip below 500. it will also happen going from reverse to park, neutral or drive. the rpms will also dip below 500 sometimes when i'm in drive and coasting down a hill.

please let me know why you guys think. thanks i'm advance

 

[tinman57]

Every once in a while depending on weather and speed, engine temp (usually just started) mine will go into overdrive and lock the converter at the same time. When it does it kind of shudders unless i get off the throttle, or give it enough to downshift. It sounds similar. Mine has over 304k on it.

 

[bmj26]

Every once in a while depending on weather and speed, engine temp (usually just started) mine will go into overdrive and lock the converter at the same time. When it does it kind of shudders unless i get off the throttle, or give it enough to downshift. It sounds similar. Mine has over 304k on it.

this issue occurs regardless of the temperature outside or of the engine. transmission problem, or injectors? not sure what the overall condition is of the transmission and i believe there may be a bad injector in the engine. when i let off the accelerator sometimes i can feel the transmission kind of like bang and then it jerks the whole truck. this is a recent issue

 

[[email protected]]

I would bet more on a trans issue. Engine should not get down to 500rpm when putting it in gear.

Do you have a scan tool of some sort to watch gear commanded and TQ converter lockup? That might help to see what is going on. I could see the truck really bogging down if it is shifting into OD and locking the converter at 40mph. You should be going a little faster before OD comes.

 

[bmj26]

I would bet more on a trans issue. Engine should not get down to 500rpm when putting it in gear.

Do you have a scan tool of some sort to watch gear commanded and TQ converter lockup? That might help to see what is going on. I could see the truck really bogging down if it is shifting into OD and locking the converter at 40mph. You should be going a little faster before OD comes.

this issue can come in one of two ways. the first way is i hit 40mph and it's still running strong, then i let off accelerator and when i hit it again it bogs out and does it's shake. the second way is if i'm cruising up to 40mph and just about when i hit 40mph it will do its shake. i do not personally have a scan tool but i know a handful of people who do, but i'm not sure how sophisticated their scanners are. maybe time for a new transmission?

 

[[email protected]]

this issue can come in one of two ways. the first way is i hit 40mph and it's still running strong, then i let off accelerator and when i hit it again it bogs out and does it's shake. the second way is if i'm cruising up to 40mph and just about when i hit 40mph it will do its shake. i do not personally have a scan tool but i know a handful of people who do, but i'm not sure how sophisticated their scanners are. maybe time for a new transmission?

Just to make sure... Your speedo is accurate, correct?

 

[bmj26]

Just to make sure... Your speedo is accurate, correct?

i believe it is off by 2 mph

 

[MichaelPatrick]

It does sound like the tranny is getting into overdrive too soon for the engine to handle. That could make it shake like it would when shifting a standard into high gear at a speed too low for the engine to handle.

Could be a tranny issue or maybe a speed sensor?

 

[harry1shop]

no one mentioned fuel pressure under load, should be 80 psi at filter

 

[madpogue]

Necro-post....... You MIGHT see 80 psi at the regulator. 80 PSI would blow out the filter; remember, the filter is between the stages of the pump.

 

[redtopman]

Mine runs 60-65. I have a fuel pressure guage.

 

[[email protected]]

no one mentioned fuel pressure under load, should be 80 psi at filter

Should not be anything over 70psi, or else leaks will be coming shortly.

The sweet spot is usually 62-65psi.