[msnunes]

I have a strange pulsation in the drive train at around 40mph, usually when it's still in 3rd gear, after the TC locks. Sometimes it will do it in OD and a bit faster speed. This is normally at the lower end of the power band, not quite lugging, but acceleration is gradual. If I accelerate it will go away. I feels as if something is slipping...

I had my trans replaced with a factory re-man last summer, but it did it before that. Before it was replaced, I thought it was just a symptom of an old trans, maybe the TC. When the trans finally gave up, I figured that would go away with it, but I have still noticed it right along. I'm finally getting around to having my shop ride with me to experience it, as it didn't sound familiar to them.

Any ideas?

 

[bbasso]

Any codes or odd readings on the guages?
Color of trans fluid?
Enough trans fluid?
What are the operating temps (high/low) of the trans and what temps so you have this issue?

 

[msnunes]

No codes, need to double check the trans fluid but it was fine the last time I checked. Remember, it's been doing this for some time, before and after replacing the trans. Temps would be probably mostly cold, but I believe it would do it almost anytime. It doesn't have to happen if I accelerate thru that speed range without staying there very long.

 

[bbasso]

Do you have a spare CPS, try swapping it out and see what happens

 

[XRACER]

Have you looked for worn or cracked U-joints?

 

[msnunes]

Might have a spare CPS somewhere, one of the old original ones that I bought as a spare. I have to see when it was changed last, but it hasn't been a LONG time.

I had the drive shafts etc inspected not long ago, and the u-joints were fine. I now have rear-pinion wear that I need fixed, and I notice the slack when shifting into reverse, and when first taking off in drive, but that's only been in the last several months. But this symptom has gone on for quite some time, maybe a few years already.

 

[bork]

I notice mine jerks like I'm pulling a trailer, like a slight bucking. Seems, from all the searching, I've come to the conclusion, I think its the IPR sticking a tad. I've been living with it, unless it starts creating a big problem.
BTW, My torque converter doesn't lock up until I'm going 50.

 

[van_350sd]

Nunes,

If you have the centarmatic wheel balancers, you need to make sure the wheels are torqued at 120lbs. minimum and the Alcoa fitment guide says 120-140 lbs. If the wheels are not torqued at least 120 lbs. you will have issues like this. Make sure a tire shop uses and actual torque wrench breaker bar type when he does the final tightening. This is very important. My van did the same thing until I had the wheels tightened, and I even had the wheel balancers on. I think my wheels are 130 lbs to 133 lbs.

I would at least try this first since it's cheap to do. When the wheels are off balance like this it could cause the driveshaft to shake making it cause more problems. Mine did it at about 40 mph also. It was a dangerous feeling driving the van this way

 

[msnunes]

Thanks bork, it does feel like a slight "bucking" -- not like a shaking, I've had plenty of that before, with out of balance issues, and have recently had the fronts rebalanced. I'll take a closer look at the IPR...