Chugging/vibration/noise at highway speed

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Bl1zzard

Bl1zzard

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1974 Dodge Dart Swinger. Newly rebuilt 360 bored .030" turning a bone stock 904 and 7 1/4 stock rear end.

So, you can read about my rebuild of the 360 in the forums. It went well, we've been driving it a lot and I really like the power it's putting out, but I think it's leaving something on the table. It seems to have a lot a torque and gets up to highway speed pretty quickly but once you're there it feels like it's chugging like a freight train. It's very noisy and after an hour or so, I have a headache. You can feel it in the steering wheel, floors and seats, everywhere. It's not a pleasure to take on the highway.

I've had a wheel alignment and balanced all the wheels too.

What I haven't done is touched the transmission, drive shaft or rear end. Could one of these be the cause of the chugging/vibration/noise? It just seems like there is something wrong, but I have no idea where to start beyond the engine. How does one determine what is causing it.

I've checked the timing and it's bang on, plugs are nice and gray/brown after 1000 miles.
 
Have new Ujoints in and have the drive line balanced. Check your pinion angle with an angle finder while the car is on the ground may have to shim the axel housing...

How does the 904 sound when is in neutral, and in-gear stopped? If your not hearing a bunch of wheining, or fluid pressure ramps, shifts smooth but strong and trans fluid does not smell like death, your trans is mostly fine. Thay are super easy to freshen up...
 
Classic drive line vibration symptoms. I assume it does not do any of this in park or neutral, correct?
 
Scody21 said:
Have new Ujoints in and have the drive line balanced. Check your pinion angle with an angle finder while the car is on the ground may have to shim the axel housing...

How does the 904 sound when is in neutral, and in-gear stopped? If your not hearing a bunch of wheining, or fluid pressure ramps, shifts smooth but strong and trans fluid does not smell like death, your trans is mostly fine. Thay are super easy to freshen up...
Click to expand...

I was thinking that I should do something with the u joints for sure. I bet they are original and have never been changed. The 904 sounds great, no whining or smell to the fluid. I did change the fluid in the rear end when I got the car 3 years ago, that old gear oil smelled like death, it had to be original.
 
Bl1zzard said:
I was thinking that I should do something with the u joints for sure. I bet they are original and have never been changed. The 904 sounds great, no whining or smell to the fluid. I did change the fluid in the rear end when I got the car 3 years ago, that old gear oil smelled like death, it had to be original.
Click to expand...

Yeah, Ujoints. Dropping a drive line sucks.... bet that is what your feeling. also check the converter bolts.
 
Bl1zzard said:
Correct, I haven't tried dropping it into neutral at highway speed though. That should tell me a lot I think.
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Perhaps. Now we need to determine if it's drive shaft speed, or tire/axle speed. This is simple. Does it sound and feel like a heard of pissed off bumble bees? That's high frequency vibration and is indicative of drive shaft and pinion speed.

Or, is it more of a "whomp whomp" like when you get a flat tire and can feel that it's axle and or wheel and tire speed?

If you can make that determination, that will narrow it down a little more.
 
'Newly' rebuilt, right. Externally balanced engine. Correct converter & dampener used?
 
RustyRatRod said:
Perhaps. Now we need to determine if it's drive shaft speed, or tire/axle speed. This is simple. Does it sound and feel like a heard of pissed off bumble bees? That's high frequency vibration and is indicative of drive shaft and pinion speed.

Or, is it more of a "whomp whomp" like when you get a flat tire and can feel that it's axle and or wheel and tire speed?

If you can make that determination, that will narrow it down a little more.
Click to expand...

It's more of a whomp whomp for sure. I need to get it into a shop to have it looked over. The money pit never ends does it?
 
Bl1zzard said:
It's more of a whomp whomp for sure. I need to get it into a shop to have it looked over. The money pit never ends does it?
Click to expand...

Ok cool. It could be simple as a bad tire.
 
Took it for a highway cruise. Dropped it in neutral, vibration continues in neutral. Seems to be in the front end and the drive train. Noticed the hood shaking in neutral at 60 mph engine idle. I also dropped it into 1st gear from a stop and ran it at 40mph at 4000 RPM for a few blocks, no vibration. Engine seems to be running just great, no complaints there. I think I need to bite the bullet and fix up the suspension with bigger torsion bars, a larger sway bar, better shocks, leaf springs and rear shocks. Also need to replace u joints and the transmission yoke grommet/rubber sleeve (it's cracked and brittle). It would probably help to put new boots and rims on it. It has the original steel wheels and the tires are from 2003 (18 years old!).

I did spend money on the steering linkage and had all the bushings replaced and alignment down when I first got it. Even has a new steering box.
 
Put jack stands under the rear axle and run the car. If it stops the problem is in the front end somewhere, if not and it vibrates in park, its up front. If it’s ok in park then put it in gear and run it up to 2000 rpm then slip it into neutral and see if it goes away. If not take off the rear wheels and try again. Next remove the drums and try again. (Be conscious about avoiding the brake pedal) I just turned the ignition off and it stopped turning. See if you get any differences without those items. While it’s up in the air make double sure there is lube oil in the differential. Ya never know....
 
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