Did my 7.25 take a crap?

[SD_R/T]

Ok, so the last time I tried to get the Valiant going I was having some issues. Shifting into Reverse was pretty rough, and the Drive gears felt very sluggish. After looking around a little, I noticed I was missing a return spring on the throttle pressure lever. See here for a little history: http://www.forabodiesonly.com/mopar/showthread.php?t=147097

I wasn't sure if that was the problem. So today I replace the spring, fire her up and now when I shift into gear (R,D,1,2) I get a pretty decent whirring/grinding noise from the rear end. Did it crap out on me? In neutral the slanty revs up fine and there is no noise. The noise is kinda hard to describe: closest thing I can come up with is the noise an over-revved starter makes. Is that clear as mud? When it made the noise, I did not drive it (so as not to do more damage) so I can't say how it drives/sounds at speed.

When it originally was shifting hard into R, I thought about the u-joints since I've had the same problem on previous Dakotas. But I wouldn't think they'd make this horrible racket when the driveshaft wasn't even moving? But I'm not sure. I was running out of daylight.

Anybody have any ideas on what to look for/check?
It's a '68/904/7.25 with the Slant. It's new to me so I don't have much history on it (for example: like how long the PO was driving without the return spring).

 

[Bad Sport]

Well, I'm certainly no expert, but is this with the car moving or just putting it in gear? When you put it in gear does the car move? I would lean more towards a trans noise. Is the fluid full? How did you check it? Does the noise go away if you unhook the spring?

 

[SD_R/T]

Well, I'm certainly no expert, but is this with the car moving or just putting it in gear? When you put it in gear does the car move? I would lean more towards a trans noise. Is the fluid full? How did you check it? Does the noise go away if you unhook the spring?

Thanks for the reply. To answer your questions:

-The noise is when shifting into gear (not moving). I did not push the accelerator to move the vehicle due to the noise. It gets your attention.
-Fluid is full. Checked per FSM: Operating temp, in neutral.
-I did not unhook the spring, but I believe it now may be an unrelated issue, since the spring only comes into play during/after acceleration. I never had a chance to do this. I simply shifted into gear.

I'm positive the noise is coming from the rear. I had a friend put it into gear and it's certainly not coming from the trans. I got out there a little while ago and didn't feel any play from either of the u-joints, but who knows.

I did, however, see that the transmission mount is toast! It appears to have disintegrated. I can physically lift up the tail of the trans as it failed at the 'skinny' part of the of mount. I will get a replacement. Would an obliterated trans mount cause a noise at the rear end?

 

[Bad Sport]

Curious, did it do it before you put the spring on? Was the car able to move under it's own power before? If it's making a noise in the rear maybe something came loose in there. Sound has a funny way of traveling and can be hard to track down sometimes. I guess I would try to figure out if the driveshaft will turn in gear without the car moving, if not I would look at the trans for the source. Start the car, put it in gear and have someone watch the drive shaft to see if it's turning, without the car moving.

 

[SD_R/T]

Start the car, put it in gear and have someone watch the drive shaft to see if it's turning, without the car moving.

Do you mean while up on blocks?

I replaced the transmission mount this afternoon. Didn't seem to have an effect. The vehicle was on all fours when I put it in gear and it made the noise.

 

[SirDan]

Check it on the ground, if your driveshaft is spinning and the car isn't moving you blew the rear. if you look and the driveshaft isn't moving and the car isn't moving you can assume the rear isn't blown up.

 

[magnumdart]

Sounds like this car might not go anywhere even a foot or two. Leave the car on the ground, start it, have someone look under it while you put it in gear, (keep foot on brake). If the drive shaft moves at all the diff is probably bad. Small amount of movement with a clunk, maybe u-joint.This should be easy to diagnose, but the repair could set you back.

 

[SD_R/T]

Thanks for all the replies. Before I ran out of light, I had a friend get in and put in gear while I looked underneath (car on the ground and brakes ON). When it is put in gear, the driveshaft starts to move slightly but stops immediately (not even a 1/4 rotation). Once it stops, that's when the noise kicks in. I paid special attention to the noise and it's location: definitely aft of the trans.

Curious, I went and performed the same experiment on my Dakota. Same thing: Once the trans was put in gear, there was a very slight movement to the driveshaft. Albeit with no noise like the Valiant.

Again, I appreciate everyone's input. Is my next step to replace the u-joints?

 

[magnumdart]

So this car is in gear, brakes applied, running, driveshaft not turning, making noise, noise is not from trans but somewhere further back? Is this a good assessment? Baffling. I once let my Dart get so far out of tune that when it was idling in gear the tailpipe would pound on the floorboard.

 

[Johnny Dart]

Why not just take the rear end cover off and give her a looksie ?

 

[caferacerx]

if the driveshaft is NOT turning, and the wheels are NOT turning
then the rear is not turning and CANT be making any noise

I would check for loose T/Q bolts, or cracked flex plate, to start

 

[Johnny Mac]

pulling the diff cover is going to tell the tale, i think you also need to see if it moves under its own power also...even pushing it in neutral w/o the car running should produce this mystery noise if its the carrier...or better yet put it in neutral, and then jack up the rear, spin the tires by hand (both forward with you and a buddy to simulate rolling down the road) and the noise should be easy to source...if its a u joint you can grab the driveshaft in park and it'll be excessively sloppy....anyways lucky for you ppl give those 7.25's away ( i know i have) so finding a new center section, or complete rear for free/cheap will be easy.

 

[caferacerx]

pulling the diff cover is going to tell the tale, i think you also need to see if it moves under its own power also...even pushing it in neutral w/o the car running should produce this mystery noise if its the carrier...or better yet put it in neutral, and then jack up the rear, spin the tires by hand (both forward with you and a buddy to simulate rolling down the road) and the noise should be easy to source...if its a u joint you can grab the driveshaft in park and it'll be excessively sloppy....anyways lucky for you ppl give those 7.25's away ( i know i have) so finding a new center section, or complete rear for free/cheap will be easy.

re read what he said THE DRIVESHAFT AND WHEELS ARE NOT TURNING! he has his foot on the brakes, so it cant be the rear causing the noise,

 

[SD_R/T]

So this car is in gear, brakes applied, running, driveshaft not turning, making noise, noise is not from trans but somewhere further back? Is this a good assessment? Baffling. I once let my Dart get so far out of tune that when it was idling in gear the tailpipe would pound on the floorboard.

It is baffling. I'm not above admitting that my ears might be deceiving me. I listened from in front of both rear wheels and it sounded the same. It is on a concrete driveway with walls nearby. Perhaps it is coming from further forward. Or perhaps there is a vibration starting further forward at the tranny and culminating in a noise further back.

Why not just take the rear end cover off and give her a looksie ?

That was on my list but ran out of light :grin: Pulling the disintigrated tranny mount out of the crossmember took longer than anticipated.

if the driveshaft is NOT turning, and the wheels are NOT turning
then the rear is not turning and CANT be making any noise

I would check for loose T/Q bolts, or cracked flex plate, to start

Sounds logical and reasonable to me, which is why I had doubts about the rear u-joint because it wasn't moving at the time of the noise.

pulling the diff cover is going to tell the tale, i think you also need to see if it moves under its own power also...even pushing it in neutral w/o the car running should produce this mystery noise if its the carrier...or better yet put it in neutral, and then jack up the rear, spin the tires by hand (both forward with you and a buddy to simulate rolling down the road) and the noise should be easy to source...if its a u joint you can grab the driveshaft in park and it'll be excessively sloppy....anyways lucky for you ppl give those 7.25's away ( i know i have) so finding a new center section, or complete rear for free/cheap will be easy.

I will keep farting around with it and gathering more detailed info/symptoms.

 

[SD_R/T]

I would check for loose T/Q bolts, or cracked flex plate, to start

Just curious, but would these problems have any effect on Neutral? I can rev it up nice and good in N with no noise. Only when put into gear.

 

[Johnny Dart]

Looked at your other thread.
The spring you are missing is for your kick-down to the trans.
Very important spring, hopefully you didnt fry your trans running without it.

 

[SD_R/T]

Looked at your other thread.
The spring you are missing is for your kick-down to the trans.
Very important spring, hopefully you didnt fry your trans running without it.

Yep. Came like that from the PO so I have no way of knowing how long it was driven around like that, unfortunately. :sad10: It's only been around the block (literally) once since I got it.

I replaced the spring, but hopefully not too late. When I earlier had replaced the trans fluid, it seemed kinda tired but not overly cloudy or full of shavings. But who knows. It's still new (to me) and I'm trying to track down all these gremlins.

 

[Bad Sport]

Check it on the ground, if your driveshaft is spinning and the car isn't moving you blew the rear. if you look and the driveshaft isn't moving and the car isn't moving you can assume the rear isn't blown up.

Yes, this is what I meant.

 

[SD_R/T]

Small update:
Had a few minutes when I got back from work and put her up in the air. Put her in neutral, parking brake off, and attempted to spin the wheels manually to see if I could get some noise.

Driver wheel: Spun freely, driveshaft spun freely. No noises. Passenger wheel did not spin at all while spinning Driver wheel (either same or opposite direction).

Passenger wheel: Did not spin at all. Putting a bar on a lugnut, I was able to barely get it to move. I mean barely. I noticed the Driver wheel spun in the opposite direction when I did this. Hmm. Stuck brake?

I ran out of time and dropped her back down. I'm hoping to find a little time this weekend to pop the differential cover and perhaps now look at the brake. Also hoping to look further forward at the TC bolts and flexplate in case my ears were deceiving me as to the location of the noise. Can I make a decent assessment of these from the inspection cover area?

Hopin' everyone's weekend is getting off to a nice start! :drinkers:

 

[Bad Sport]

I would check the brake first, it could be hung up.

 

[Gnome]

I get a pretty decent whirring/grinding noise

re read what he said THE DRIVESHAFT AND WHEELS ARE NOT TURNING! he has his foot on the brakes, so it cant be the rear causing the noise,

i agree with caferacerx at this point the only thin that can make that noise with the brake ON is inside the trans area.

IMO time for a rebuild.

 

[Gnome]

I noticed the Driver wheel spun in the opposite direction when I did this. Hmm. Stuck brake?

Hopin' everyone's weekend is getting off to a nice start! :drinkers:

that is normal with an open diff.

it could be possible that the brake is stuck not allowing the passenger wheel to move easily.

 

[SD_R/T]

Just wanted to update this since I know it can be frustrating reading a thread that you think might be able to help you out with a problem only for the OP to drop off the face of the planet.

Turns out the rear passenger drum was indeed stuck (see this thread: http://www.forabodiesonly.com/mopar/showthread.php?p=1440616#post1440616) Once I got that pulled off, the rear passenger axle would spin freely in conjunction with the driveshaft. Did not hear any funky noises while spinning it by hand. Have not dropped it down and put it in gear yet (have to rebuild the brakes first) however I'm hopeful this will alleviate the issue. Time will tell!

Appreciate all who chimed in.

 

[nuttyprof]

Pull the drive shaft and check the splines in the yoke and on the output shaft. If that's not it you probably killed your transmission. Sorry to hear about your troubles. If the drive shaft is not turning the grinding noise is not coming from your diff.