Truck feels "sluggish" and jerks a bit at 40mph

A few months ago, every time I would get to 40mph (the speed limit on the main drag coming into the residential area I live), my truck would start jerking back and forth a bit like the tranny was slipping or something. If I sped up or slowed down just 5mph on either side, it generally went away.

I ran some Amsoil Performance Improver (Pi) to it twice and it seemed to run a slight bit better, but there was the occasional 40mph jumping around, and it felt a little sluggish to respond to the throttle at times.

Two weekends ago, I made a longer trip than normal down to south, south, south (almost in Mexico) Texas. 500+ miles round trip. On the way there, it drove perfect. On the way back, it was sluggish to throttle response. When I got home, it didn't seem to be running quite right and was VERY sensitive to that 40mph zone. The next day, it felt like I had water in my gas or something.

It's a 2007 Dodge Ram Quad Cab with the 5.7 MDS Hemi with almost 90K on it.

I thought it was a transmission issue at first, but my buddy thinks it's my engine. He said he recalled something about the fuel pump / injectors doing something at 40mph.

Any recommendations? My dealer always wants to do that "fuel rail treatment" to my truck, which I have been told is worthless, but now I'm not so sure.

All the best,
Glenn

Welcome bud, with 90k you are due for plugs, wires and coil boots unless thats been done recently. Tb will also cause the truck to feel sluggish and that can be cleaned, the cylinders kicking out not being under load could also give you the sluggish feeling. What fuel are you running also?

Thanks for replying.

I had the plugs changed out not too long ago (or at least it seems it wasn't that long ago). I'll break out the service paperwork and check the date. I don't think I had wires done at that time though.

I always run 89 octane (Valero brand here in Texas) in it, but on the way back from Harlingen TX, I stopped at a very old looking Valero station to gas up. Wondering if I got some bad gas there that compounded the problem.

Is cleaning the TB on my 07 pretty easy? I did it myself on my 03 with the 4.7.

All the best,
Glenn

it is very easy, take off the intake and then only 4bolts holding the TB in.
could also try out sea foam aswell, that could help.
and if it seems to be slipping, take the trans dipstick out and make sure its pink and doesnt smell burnt/have metal shards in it. could also just do a trans flush and look for metal shards.
poor gas could be the reason too.
see if it is showing any codes too.
turn the key all the way but do not start the truck and then turn it back off. do this 3times in a row and see if anything shows up on the mileage.

^yup

I lost this post for a little while, but finally found it. Trans fluid looks clean. Very light pinkish tint to it. No burnt smell, and at the proper level.

Not showing any codes. Starting early this week, it's now doing this at almost any non-highway speed.

I'll clean the TB this weekend, but have a feeling it's going in the shop soon.

All the best,
Glenn

Good luck with the TB cleaning, let us know how you make out.

Make sure you use brake cleaner and avoid the electronics at alllllllll cost there is a how to in the DIY section

When was the last time you had trans filters changed? I had this sort of thing happend once and I had a broken trans filter that messed with torque converter. Maybe not in this case but just an idea it is smart to change filters anyway.

Do you have an aftermarket cai or oiled reusable filter?
when was the last time the trans was serviced? (Pan dropped, filters replaced)
cruise control still work fine?

All good advice above. I'm really curious if your truck would still act this way if you dropped it out of MDS. Mine does some strange things similar to what you are describing when it is right at the switch over point. Pause, speed up, slow up, sluggish. Mostly in town. Occaisionally on the highway. In town I've started using the manual gear select bump it to 5. Never happens now. Just my 2 cents.
Jay

I tried some various things this week. Ran some fuel treatment through it again, filled up with premium to see if that would help. No change.

Cruise control still works fine, but when I put it on cruise at 40mph, the truck surges. It maintains 40mph, but it's like the engine / transmission is struggling to find the right gear / rpm's to keep me there.

Ran the truck with the OD off to see if that would make a difference - none noted.

So, I did what I should have done a long time ago and looked through my service records. There was NO WAY that it was time for a service. Well... I was wrong. I'm slightly over my mileage / timeframe for a tune up, transmission service, and transfer case service. So I brought it to the shop this morning for all three. They called a few hours later to tell me that my throttle body was "pretty darn filthy", and needed to be cleaned badly. So I had them do a complete cleaning of the fuel system components.

Got it back this afternoon, and the truck is no longer "sluggish". I have my power back. It feels like my truck is newer. However, at 40mph, it still would do that surging thing. It doesn't seem as bad as before, but it still was doing it. Then I turned off the A/C - it stopped doing it. Hmmmm.... I need to drive it more to find out, but I think I may have just stumbled onto something.

Anyway, it's running much better. I'm still worried about that 40mph surge though.

All the best,
Glenn

Compressor dragging or going out possibly?

That's where I was going. Not sure, as it hasn't been making noise or anything, but it's definitely something I'm going to look into.
All the best,
Glenn

Hi I am new here and came across your problem. I was wondering if you have found the problem yet. It sounds like we are having the same issue. Mine seems to show its ugly head between 40 and 55mph after I have let off the gas then start to apply slowly. If I give it a lot of gas it stops. Mine started right after I had the trans serviced so I thought it was the trans. Took it back and had the guy (friend of mine) test drive it and he said it was't the trans slipping, He said if it was there would be a fluctuation in the RPM and there isn't.

My truck does this same jolting and jerking right after it shifts from fourth into fifth gear.every time it does it, I hit the tow haul button and it instantly goes away. Sometimes it does it on flat ground after it shifts, but mostly on hills. I ran sea foam through it and my throttle body is clean. I didn't think it was the transmission, and I'm glad to see that everyone else seems to agree. Going to just take it to the mechanic and see what we can't have done about it.

Similar issue with my truck as well. I do have a P0868 tranny low line pressure code though.
Keep us posted if you figure out what is going on.


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