OBS bogs down in reverse

[jjsalz]

Guys,

Curious if any of you have seen this issue before. Truck idles real good, but when I shift into reverse, it noticeable bogs the engine down, almost stalling, but recovers. My batteries were bad previously, and the engine would actually die before. New batteries it doesn't die, but comes close. Any ideas? It's a 1997 F-250, stock E4OD transmission, 4x4, 145k miles, it doesn't bog down in the other gears.

https://youtu.be/FqBZ65kKlww

 

[BrewTown]

I watched the vid, man I really wanted you to shift into the other gears...
I guess I'd be researching a transmission issue? Does it drive normal in all gears?

I don't have great experience with this but 2 things come to mind.
1. possibility of a cross leak or hard parts failure in the trans causing a partial converter clutch apply in reverse
2. Range sensor not sensing reverse and compensating the idle.

I don't know if either make sense, however it may spark something?
I know 7.3s aren't as sensitive, but any electronically controlled vehicle needs good operating voltage for the sensors to operate in range. You mention dead batteries, have you tested volts while running to make sure the alternator is working? All your grounds good and clean? Winters/salt are hell on everything here in WI...

 

[jjsalz]

Thanks a ton for the response! Yeah the reason I didn't shift into the other gears in the video is because it just sounds normal. Just goes into gear. Which makes this problem kind of peculiar. As far as the voltage is concerned, these are two brand new batteries which have full normal voltage. These batteries start the truck better than my other ones ever have to be honest.

I'm so unfamiliar with tranny parts/what could be causing this that I'm kind of stuck. I don't want there to be a major problem that is going to leave me stuck on the road. Grounds I believe are real good, but I don't know how many there are other than all the obvious ones that I visually and electrically test with my meter. My fear is some hard parts failing within the tranny are causing the problem. The truck drives excellent in all the gears, including reverse, it just bogs the engine down like that for a second. Super weird.

 

[Gnathv]

When you shifted into reverse your voltage gauge jumped negatively. I don’t know if this could be caused by solinoid pack or what, just noticed it.

 

[BrewTown]

I'm referring to if the alternator is charging. If you have a multimeter, fully charged batteries should be 12.7v, but at idle running you should get 13.6 to 14.4 if the alternator is working. This should be checked before anything! Also checking for good clean grounds is free

I also noticed that gauge jump when you shifted. I don't know what would cause that. I could speculate, but that's all it would be.

 

[jjsalz]

When you shifted into reverse your voltage gauge jumped negatively. I don’t know if this could be caused by solinoid pack or what, just noticed it.

Yeah I feel that negative jump should be indicative of what the problem is, some sort of heavy electrical load as soon as I go into reverse. Unless that drop is simply the alternator charging voltage going away because of the loss in RPMs? What do you think?

I'm referring to if the alternator is charging. If you have a multimeter, fully charged batteries should be 12.7v, but at idle running you should get 13.6 to 14.4 if the alternator is working. This should be checked before anything! Also checking for good clean grounds is free

I also noticed that gauge jump when you shifted. I don't know what would cause that. I could speculate, but that's all it would be.

Yeah I'll check the voltage while it's running just to be sure it's good and proper. Visually, it looks correct by the gauge, but it's best to test it with my meter. Do you think the negative drop on the voltage gauge is caused by a temporary high electrical load, or the alternator voltage dropping out because of the loss in RPMs?

Thanks for the replies guys, I really appreciate it.

 

[BrewTown]

Do you have a way to read gear? My cts2 will say what gear I'm in, just to make sure the pcm is seeing a gear and adjusting idle as necessary.

Unless you're thinking the reverse lights are creating a huge electrical load? Range sensor shorting. Short in the column when you hit reverse... should I keep spitballing?
Welcome to diagnosis over the internet!

 

[webb06]

Does the torque converter lock and hold as it should when driving? Might be the converter locking up in reverse. Which I have seen.


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[Mark Kovalsky]

It is almost certainly the converter partially locking causing the engine to bog.

The converter will partially lock if the pressure to the converter drops. The pressure can drop for several reasons. Low trans fluid, improperly installed internal filter, leaking seals on the input shaft, or a worn pump.

You could put a pressure gauge in the test port and see if the pressure drops going into reverse.

The voltage gauge dropping is probably due to the RPM dropping.