In need of help...

[69Gonzo]

I'm having some trouble with what feels like misfiring when downshifting... it normally only happens between 40 and 55mph. At first I thought it was my diff, because it felt like it was shifting a little rough, I changed the diff fluid today and it's shifting smoother but the problem persist... Anyone got any tips?

 

[1sweetSVT]

Have you pulled the plugs to check them out? Fuel filter? What have you looked over so far?

 

[throttle jockey]

Since you're downshifting I'm guessing this means its happening during deceleration when you're not on the throttle. If its not misfiring under acceleration and load then its probably not misfiring during deceleration in the absence of load. Could it be trans related based off what you're feeling? That would be my guess if there's any issue at all.

 

[69Gonzo]

Fuel filter and plugs are next inline;-)

 

[69Gonzo]

Since you're downshifting I'm guessing this means its happening during deceleration when you're not on the throttle. If its not misfiring under acceleration and load then its probably not misfiring during deceleration in the absence of load. Could it be trans related based off what you're feeling? That would be my guess if there's any issue at all.

My pop thinks I should put Lucas trans treatment in, but I really don't think it's the trans. Its acting somewhat the same way it did before I blew a plug. I'm gonna start with the fuel system and ignition then go from there. Just wanted to see if any of you guys had similar problems. I was hoping maybe it was something stupid I was overlooking, like a dirty vacuum tube, but I guess I'm starting the process of elimination today. Thank you guys for your input, it's very much appreciated.

 

[throttle jockey]

You didn't clarify if its happening during acceleration, deceleration or both. I am quite confident it has absolutely nothing to do with the differential based of your description.

I don't think its fuel or fire related based off what you've provided to us so far which is why I asked for clarification. When Belle was my DD I always replaced the fuel filter with every oil change and replaced plugs every 5,000-8,000 miles so I won't discourage you from doing those basic maintenance items regardless. Heidi isn't modded to the extent that Belle is so she doesn't get quite the same attention. Heidi gets a fresh fuel filter every-other oil change and I'll go 20,000 miles or so before I replace the plugs.

 

[69Gonzo]

You didn't clarify if its happening during acceleration, deceleration or both. I am quite confident it has absolutely nothing to do with the differential based of your description.

I don't think its fuel or fire related based off what you've provided to us so far which is why I asked for clarification. When Belle was my DD I always replaced the fuel filter with every oil change and replaced plugs every 5,000-8,000 miles so I won't discourage you from doing those basic maintenance items regardless. Heidi isn't modded to the extent that Belle is so she doesn't get quite the same attention. Heidi gets a fresh fuel filter every-other oil change and I'll go 20,000 miles or so before I replace the plugs.

It happens under deceleration normally it happens between 40 to 55 mph but the past few days it happened around 20 mph and in reverse under my first start up of the day, I never have any problems under power. One of the reasons I thought it was my diff was the rear main seal is leaking and from the drivers seat it feels kinda like an abrupt gear change in conjunction with a misfire. After next weeks paycheck, I'll handle the rest of my basic maintenance then if the problem persist I'll try a transmission flush. Thanks for your input dude, sorry if I was being a little vague in my description.