70 duster rear brake drum/vibration question

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Shadowfirexz

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Hello... I have a 1970 Plymouth duster. 340 4 speed. New clutch, rebuilt a833, new trans mount, new “balanced” driveshaft with new ujoints, rebuilt 8-3/4. Pinion angle checked and set. New brakes, wheel bearings, wheel studs and drums.
I have 2 questions I need help with. I’m chasing a high speed vibration. Ready to burn car lol.
At 130km or 80 mphish the car developes the most violent vibration I’ve ever experienced. I can’t push through it and have to back off immediately or the world is gonna end. At this moment it hits The shift lever, clutch pedal and floor are experiencing brutal vibrations. Feels like it’s coming from the trans area but everything on car is new and aligned. Runs perfect at lower speeds. At 100km a slight vibration starts but I can pull outa it. At 130 she’s done!!!! 4th gear it happens in nothing changes if I push the clutch and pull into neautral vib still there in or outa gear while at that speed...... A hot rod that can’t go fast uhg ready to bail from the Abody world as this vibration has cost me thousands in Trying to sort out.

I’m running 14x5.5 ralleys small bolt pattern. I’m not suspicious of a slightly bent rim as I bought these used. Ordered new rims from wheel vintiques they are 4 weeks away here in Canada. Sadly I can’t change the tires/ rims yet. So that’s my 1sts suspicion although the vibration to me doesn’t seem like a wheel as it’s felt on the shift lever and clutch pedal mostly.

A while back I bought a set of 10 inch brake drums from classic industries. One drum has maybe a couple oz weight the other has massive weights!!!!!! It makes me suspicious the darn drum is outa wack!!!!!!

These drums fit goofy to the backing plates as they touch in the odd spot. Grinded the plate to clear in few spots which sickened me..... where do you guys get your rear 10 inch brake drums for these abodies? Small bolt pattern 5x4 so I’ve learned options are skimpy but come on Gotta be some that work better....??? The old 10 inch bell drums I had were toast!!!!! Anyone make rero bell drums for my 8-3/4? Also no I’m not into spending a dime in changing bolt patterns to gain more options, just looking for sbp options. Anyone have some good shape 10 inch sbp bell drums they wanna ship up to Canada? Lol.
Very suspicious of the drums I’ll attach a couple
Pics and you can see the diff weights on each drum it looks suspicious to me and at 80mph could be a vibration nightmare ??????

Help with some advice? At the end of my rope chasing this vibration

D5B2F47E-1849-4660-84DF-C08442B276C7.jpeg
 
Shadowfirexz said:
Hello... I have a 1970 Plymouth duster. 340 4 speed. New clutch, rebuilt a833, new trans mount, new “balanced” driveshaft with new ujoints, rebuilt 8-3/4. Pinion angle checked and set. New brakes, wheel bearings, wheel studs and drums.
I have 2 questions I need help with. I’m chasing a high speed vibration. Ready to burn car lol.
At 130km or 80 mphish the car developes the most violent vibration I’ve ever experienced. I can’t push through it and have to back off immediately or the world is gonna end. At this moment it hits The shift lever, clutch pedal and floor are experiencing brutal vibrations. Feels like it’s coming from the trans area but everything on car is new and aligned. Runs perfect at lower speeds. At 100km a slight vibration starts but I can pull outa it. At 130 she’s done!!!! 4th gear it happens in nothing changes if I push the clutch and pull into neautral vib still there in or outa gear while at that speed...... A hot rod that can’t go fast uhg ready to bail from the Abody world as this vibration has cost me thousands in Trying to sort out.

I’m running 14x5.5 ralleys small bolt pattern. I’m not suspicious of a slightly bent rim as I bought these used. Ordered new rims from wheel vintiques they are 4 weeks away here in Canada. Sadly I can’t change the tires/ rims yet. So that’s my 1sts suspicion although the vibration to me doesn’t seem like a wheel as it’s felt on the shift lever and clutch pedal mostly.

A while back I bought a set of 10 inch brake drums from classic industries. One drum has maybe a couple oz weight the other has massive weights!!!!!! It makes me suspicious the darn drum is outa wack!!!!!!

These drums fit goofy to the backing plates as they touch in the odd spot. Grinded the plate to clear in few spots which sickened me..... where do you guys get your rear 10 inch brake drums for these abodies? Small bolt pattern 5x4 so I’ve learned options are skimpy but come on Gotta be some that work better....??? The old 10 inch bell drums I had were toast!!!!! Anyone make rero bell drums for my 8-3/4? Also no I’m not into spending a dime in changing bolt patterns to gain more options, just looking for sbp options. Anyone have some good shape 10 inch sbp bell drums they wanna ship up to Canada? Lol.
Very suspicious of the drums I’ll attach a couple
Pics and you can see the diff weights on each drum it looks suspicious to me and at 80mph could be a vibration nightmare ??????

Help with some advice? At the end of my rope chasing this vibration

View attachment 1715386854
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Look at the weights on the bottom drum va the top drum!!!! Like wtf is going on that’s a lot of extra weight on that bottom drum or am I nuts?
 
Murray said:
Drive shaft.
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Just had a new driveshaft built by a reputable drive line shop. Got shaft from shop put in car, vib still there. Brought it back to shop saying I want it rechecked. They balanced again .. I reinstalled vib still there. New spider u joints as well. Was like 2000thousands runout on shaft If I recall that’s pretty reasonable.... old shaft was 2-3/4 I had a 3 inch tube built. Used old slip yoke was in good shape. Had to lengthen shaft as old shaft was too short. When I install driveshaft I slide into trans have about a inch clearance to mount in dif so that’s about right. Do t think shaft is in to far it’s sitting where it should be vs barely hanging on like the old shaft. I’m doubting driveshaft as it’s dialed in and been rechecked a couple times. Although it does to me feel shaft related I just don’t know as it’s all within spec ??? Uhg
 
Bad Sport said:
How about axle end play, is that set properly?
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Just put a new Yukon power lock posi in the 8-3/4 new axle bearing/seals end play adjuster. End play was set properly few thousands play.... can you see the picture of my brake drums? Any opinion on the gigantic weights on one drum vs the other drum. Does that not seems highly suspicious that when I hit 80mph that drum is starting to do the wobble gobble with all those weights on one end? And can’t just run out and balance a drum everyone laughs when I ask saying no one balances drums go buy new ones. Ya well buying a 5x4 bolt pattern drum isn’t just a trip down to the quickly mart part ... lol.
 
Pilot bushing in the crank ! I had the same problem the input shaft would wobble in the crank, in 4th gear it's straight through so the tail shaft wobbled causing the drive shaft to wobble in the front and it set off a bad, bad vibration. 3rd gear it's not straight through so the wobble would cancel out. change the bearing and it went away for a while then come back. I found the bell was off center and would wipe out the pilot after a short while. I had to put in offset dowels .020 and that fixed it.
 
brian6pac said:
Pilot bushing in the crank ! I had the same problem the input shaft would wobble in the crank, in 4th gear it's straight through so the tail shaft wobbled causing the drive shaft to wobble in the front and it set off a bad, bad vibration. 3rd gear it's not straight through so the wobble would cancel out. change the bearing and it went away for a while then come back. I found the bell was off center and would wipe out the pilot after a short while. I had to put in offset dowels .020 and that fixed it.
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brian6pac said:
Pilot bushing in the crank ! I had the same problem the input shaft would wobble in the crank, in 4th gear it's straight through so the tail shaft wobbled causing the drive shaft to wobble in the front and it set off a bad, bad vibration. 3rd gear it's not straight through so the wobble would cancel out. change the bearing and it went away for a while then come back. I found the bell was off center and would wipe out the pilot after a short while. I had to put in offset dowels .020 and that fixed it.
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wouldnt it wobble at any speed and vibe in and speed in 4th then? Mine runs smooth as can be in 4th until you hit 80mph then nothing stops the vibe just lowering speed .... My bellhousing has dowls and I believe it to be aligned right. Never touched any crank bushings ever hmm.
I can’t say your wrong and I can’t say you’re right uhg, what a nightmare. Thanks I’ll keep digging
 
Shadowfirexz said:
wouldnt it wobble at any speed and vibe in and speed in 4th then? Mine runs smooth as can be in 4th until you hit 80mph then nothing stops the vibe just lowering speed .... My bellhousing has dowls and I believe it to be aligned right. Never touched any crank bushings ever hmm.
I can’t say your wrong and I can’t say you’re right uhg, what a nightmare. Thanks I’ll keep digging
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I'm just saying what happened to me and what fixed it. In 1st 2nd and 3rd the input shaft is spinning at a different speed than the output shaft, so if the input wobbles the output shaft is turning slower then the vib seems to cancel it self out and you might not feel it but in 4th gear the two shafts are turning the same speed and it is like a straight shaft that gets bent in the middle, now if you put a bearing on both ends and spin it the middle swings out of round and both ends wobble. if it's not out much you might not feel it till it gets going fast enough to set up a oscillation then its hard to stop.
If you put everything in new and didn't change or check the pilot it could just be worn out. Is it a bushing or a ball bearing ?
 
brian6pac said:
I'm just saying what happened to me and what fixed it. In 1st 2nd and 3rd the input shaft is spinning at a different speed than the output shaft, so if the input wobbles the output shaft is turning slower then the vib seems to cancel it self out and you might not feel it but in 4th gear the two shafts are turning the same speed and it is like a straight shaft that gets bent in the middle, now if you put a bearing on both ends and spin it the middle swings out of round and both ends wobble. if it's not out much you might not feel it till it gets going fast enough to set up a oscillation then its hard to stop.
If you put everything in new and didn't change or check the pilot it could just be worn out. Is it a bushing or a ball bearing ?
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Pilot bearing was changed along with the fly wheel got turned, new clutch and rebuilt 833 about 300km ago few months. Everything’s new but not saying that means it’s right. Big damn job tearing down again to go through new stuff. Does anyone have any opinions on the brake drum pic I posted regarding the ridiculous weights on the one drum. I mean if that’s out it would send a violent vibe through the axles, dif and driveshaft right into the trans area ..
 
Put it up on jack stands, pull the drums off and run it up to 130km and see if it vibrates, just don't hit the brake pedal with the drums off. Just put it in neutral when it slowing down.
 
brian6pac said:
Put it up on jack stands, pull the drums off and run it up to 130km and see if it vibrates, just don't hit the brake pedal with the drums off. Just put it in neutral when it slowing down.
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I’m tempted but a bit to dangerous for me to pull 130km on jack stands and no brakes.

I discovered something today with this driveshaft.... put it in a driveline shop today to try and help diagnose this issue. After close inspection it appears the phasing is off. The ujoints are a couple degrees off and should be even to each other. Like the driveshaft is twisted or they welded it up a bit off when they built it. They say that would cause a vibration. Then they ran it on the rack and we visually could see a wobble in the shaft. It appears this may be shaft related. The outfit that built the driveshaft will be building a entire new shaft to try and make up for this bs first one. Sadly I’m leaving to work for 2 weeks so when I get back I’ll install the new shaft and put a update here as to if it fixes the vibe. Thanks everyone this I a really cool site
 
Fishing68 said:
any updates?
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Well I found a few things but can’t test the car until the spring, lots of snow here in Bc. I found a couple stripped bolts on a Ralley wheel centercap which was causing a lot of the high speed vibe. At high speed that darn centercap started going nuts wobbling around. Ended up buying a whole new set of ralleys from wheel vintiques with new center caps and retired the 50year old original ralleys. It did make a huge difference but some vibration still there.


Pulled new driveshaft again found the phasing was off a bit. Had another built with brand new spicer Ujoints and a new slip yolk also, it’s looking perfect so I’ll be trying that in the spring and see if I can get the rest of the vibe gone. I’m still kind of suspicious of the weights on the rear drums as one drum has substantially more weights. I may convert to rear disc this year also. Entire suspension and driveline from flywheel back is new. Everything’s been checked 5 times over so not sure what else could be causing the vibe. The vibration is 80% better after rebuilding the rear end and fireplace going the old wheels with that one bad centercap. I’ll update this further in the spring when the car comes out and I try the 2nd new driveshaft. Have nothing left to replace but the engine in this duster.
 
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