Kind of Off Topic

[Moseman]

I hope I can plumb the collective experience and knowledge on this site. My 77 Cordoba has a high frequency vibration shortly after starting up from a stop, starts to kick in at about 20 mph, continues from there and on. Here is what we have done so far:

1. Total front suspension rebuild, idler arm, bushings, tie rod ends, ball joints, steering box.
2. New ESPO rear springs (second new set, trying to solve by correcting pinion angle)
3. new u-joints
4. new tires/balance

Okay what do we do next? Pull and rebalance driveshaft? Could there be a rear differential problem? Or do I pull and replace front rotors?

Any thoughts?

 

[Pete Kaczmarski]

Will it have the same vibration while in Park and given same RPM's? if so start more basic like listening with a stethoscope to the items connected to the drive belts. If no stethoscope then disconnect them. If does not do it at an idle then put on hoist and give it some RPM's. Can't hear it? then in something that is connected to the tires.

 

[1978 NYB]

Is the wheel bearing adjustment correct?

Have you inspected the U-joints? No slop in the caps? Inspect the driveshaft for any appearance of weights falling off.

 

[Moparwilks]

Had a Dakota that had that problem. It was the back u joint. They can go bad without slop. Just a few rusty needle bearings is all you need to do the trick.

 

[Moseman]

Will it have the same vibration while in Park and given same RPM's? if so start more basic like listening with a stethoscope to the items connected to the drive belts. If no stethoscope then disconnect them. If does not do it at an idle then put on hoist and give it some RPM's. Can't hear it? then in something that is connected to the tires.

No vibration in park, and yes, I thought about running the drivetrain while on hoist.

 

[Moseman]

Is the wheel bearing adjustment correct?

Have you inspected the U-joints? No slop in the caps? Inspect the driveshaft for any appearance of weights falling off.

We haven't seen any evidence of thrown weights, and the two u joints were replaced chasing this problem. No joy.

 

[Davea Lux]

Sometimes a bad planetary gear set in the transmission can cause a significant vibration. When you have the car on the hoist, grab your stethoscope and listen to the center of the transmission case. If the noise is is not coming from there listen to the rear axle (from the back side). Note: A spinning drive line has the potential to cause serious injury or death! Be very careful. And this is obviously a two person job, pick someone responsible.

Dave

 

[Clover]

Sounds like torque converter shudder. It’s trying to lock up but won’t quite do it.

 

[Davea Lux]

You do not need to replace the rear springs to correct a pinion angle. There is a wedge shaped insert that is placed between spring and mount pad to correct this problem. A lot cheaper than new springs. Unless the pinion angle is so far off that the u-joints are hopping the rear axle up and down, I do not think that is your vibration issue.

Dave

 

[Moseman]

You do not need to replace the rear springs to correct a pinion angle. There is a wedge shaped insert that is placed between spring and mount pad to correct this problem. A lot cheaper than new springs. Unless the pinion angle is so far off that the u-joints are hopping the rear axle up and down, I do not think that is your vibration issue.

Dave

Dave, I wish it was so. Two frame/alignment shops could not do the wedge thing. The Cordoba springs are sandwiched between two large rubber isolators. I am thinking that your comment about the transmission may be the problem. I bought the car in Portland, OR last April or May and drove to New Mexico. Shortly after that, it crapped out the trans. fluid due to a dried up gasket. (second 727 trans. to do that to me, both on Cordobas) I wonder, if there are more problems inside that trans???

 

[Davea Lux]

The '77 Cordoba has a "Low Slip" torque convertor, it does not lock up as the '78 and later models did. Just in case somebody changed transmissions, if you have a failing lock up convertor, you will usually get a shudder when it tries to apply. Usually there will be significant debris in the transmission pan if this is the case. A bad clutch pack or bad convertor lining usually leaves enough debris to be obvious.

Dave

 

[Davea Lux]

Dave, I wish it was so. Two frame/alignment shops could not do the wedge thing. The Cordoba springs are sandwiched between two large rubber isolators. I am thinking that your comment about the transmission may be the problem. I bought the car in Portland, OR last April or May and drove to New Mexico. Shortly after that, it crapped out the trans. fluid due to a dried up gasket. (second 727 trans. to do that to me, both on Cordobas) I wonder, if there are more problems inside that trans???

Losing the transmission oil usually will not kill the planetary gears, The transmission will stop moving long before the gears run dry enough to fail. I would pull the pan if the transmission is determined to be the source of the noise. Planetary gears just wear out sometimes, but most often debris from failing clutch packs ruin them. There were no specific leakage problems to the Cordoba that I am aware of, most likely just the 40+ years of service.

Dave

 

[Moseman]

Losing the transmission oil usually will not kill the planetary gears, The transmission will stop moving long before the gears run dry enough to fail. I would pull the pan if the transmission is determined to be the source of the noise. Planetary gears just wear out sometimes, but most often debris from failing clutch packs ruin them. There were no specific leakage problems to the Cordoba that I am aware of, most likely just the 45+ years of service.

Dave

When I replaced the pan gasket, the bottom of the pan was relatively clean, just a little sludge/dirt, but jut a wipe of a shop rag took care of it. So, back to running on the lift!

 

[Davea Lux]

Dave, I wish it was so. Two frame/alignment shops could not do the wedge thing. The Cordoba springs are sandwiched between two large rubber isolators. I am thinking that your comment about the transmission may be the problem. I bought the car in Portland, OR last April or May and drove to New Mexico. Shortly after that, it crapped out the trans. fluid due to a dried up gasket. (second 727 trans. to do that to me, both on Cordobas) I wonder, if there are more problems inside that trans???

Unless you went to a lift kit type spring with a much different arch, I can't imagine how the pinion angle could be that far off unless somebody shipped the incorrect rear springs.

Dave

 

[Moseman]

You do not need to replace the rear springs to correct a pinion angle. There is a wedge shaped insert that is placed between spring and mount pad to correct this problem. A lot cheaper than new springs. Unless the pinion angle is so far off that the u-joints are hopping the rear axle up and down, I do not think that is your vibration issue.

Dave

First time I noticed the vibration was after the alignment shop replaced the tie rod ends, etc. and replaced the rear springs. Thus the suspicion about the pinion angle. We then replaced the u joints, (no joy), then I went to another shop (well respected in the area, does heavy trucks/ trailers, the owner has been in the business about 45 years). That was when we decided to go to another set of springs. Replaced tires, just to be safe. Still no success. So, now off to another shop and onto the lift. I have a two post in my shop in South Dakota. But here in New Mexico, I am a shade tree mechanic.

 

[Davea Lux]

First time I noticed the vibration was after the alignment shop replaced the tie rod ends, etc. and replaced the rear springs. Thus the suspicion about the pinion angle. We then replaced the u joints, (no joy), then I went to another shop (well respected in the area, does heavy trucks/ trailers, the owner has been in the business about 45 years). That was when we decided to go to another set of springs. Replaced tires, just to be safe. Still no success. So, now off to another shop and onto the lift. I have a two post in my shop in South Dakota. But here in New Mexico, I am a shade tree mechanic.

You probably want to find a lift that raises the car under the rear axle so the power transmission dynamics are the same as road use. (ie two post)

Dave

 

[Moseman]

Unless you went to a lift kit type spring with a much different arch, I can't imagine how the pinion angle could be that far off unless somebody shipped the incorrect rear springs.

Dave

We first had heavy duty springs from Stengel Bros., then opted for standard springs from ESPO. I reqally think we have exhausted the spring issue.

 

[1978 NYB]

The '77 Cordoba has a "Low Slip" torque convertor, it does not lock up as the '78 and later models did. Just in case somebody changed transmissions, if you have a failing lock up convertor, you will usually get a shudder when it tries to apply. Usually there will be significant debris in the transmission pan if this is the case. A bad clutch pack or bad convertor lining usually leaves enough debris to be obvious.

Dave

You can tell by the input shaft of the txsm. If it is splined all the way to the end of the shaft it is a lockup. It the first inch of the shaft is smooth then its a non-lockup. You can also tell if the valve body has a tube about the size of a brake line going across it if it's a lockup.

 

[Davea Lux]

First time I noticed the vibration was after the alignment shop replaced the tie rod ends, etc. and replaced the rear springs. Thus the suspicion about the pinion angle. We then replaced the u joints, (no joy), then I went to another shop (well respected in the area, does heavy trucks/ trailers, the owner has been in the business about 45 years). That was when we decided to go to another set of springs. Replaced tires, just to be safe. Still no success. So, now off to another shop and onto the lift. I have a two post in my shop in South Dakota. But here in New Mexico, I am a shade tree mechanic.

Since you bought an Oregon car, I will throw this out. We get a lot of water here in western Oregon and folks sometimes decide to drive thru it. Check the rear end oil for a whitish cast (moisture) Foaming gear oil can make all kinds of strange noises. (Water leaks in thru the vent if the rear axle is under water)

Dave

 

[67Monaco]

Does the vibration persist on decelleration?