Noisy rearend 69 barracuda 318 car

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fuzzman

fuzzman

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Hey all
I just finished up a 69 barracuda convertible that hasn't been on the road sense 1991 so the first test drive i noticed that the rear end is noisy i think it is either a 7 1/4 or 8 1/4 not sure but defiantly not a 8 3/4 so the back plate comes off if you have the work on it. Like i said it was sitting outside for over 20 years and when i picked it up one the threat wheels was frozen to the brake shoes. So today i drained the fluid out of the pumpkin and put some MOPAR 90 weight lube in there to replace the nasty stuff that came out. My question is is there any additive i can add to help quiet it down? The car only has 60 thousand original miles on it so i think it might just need some drive time to help it out. Any suggestions would be deeply appreciated
Pat Faley
67 NB S Clone
69 Barracuda convertible
East Peoria IL
 
fuzzman said:
Hey all
I just finished up a 69 barracuda convertible that hasn't been on the road sense 1991 so the first test drive i noticed that the rear end is noisy i think it is either a 7 1/4 or 8 1/4 not sure but defiantly not a 8 3/4 so the back plate comes off if you have the work on it. Like i said it was sitting outside for over 20 years and when i picked it up one the threat wheels was frozen to the brake shoes. So today i drained the fluid out of the pumpkin and put some MOPAR 90 weight lube in there to replace the nasty stuff that came out. My question is is there any additive i can add to help quiet it down? The car only has 60 thousand original miles on it so i think it might just need some drive time to help it out. Any suggestions would be deeply appreciated
Pat Faley
67 NB S Clone
69 Barracuda convertible
East Peoria IL
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50 years ago I was hich hiking to Alaska and got a ride in this box truck that had a real noisy rear.We stopped at this garage in this place out in the middle of nowhere and the old guy who was working there suggested we put in a LB of powered graphite to quiet it down.It worked and we continued for 1200 miles up to where they dropped me off without any noise or problems . You might want to try a Moly additive like Cal Guard . I use it in all my standard transmissions and my 71 chevy trucks rear and my shaft drive motorcycles rear ends . It coats the gears and keeps them lubed.
 
Generally if pinion seal wasn't leaking and it had fluid in the gear case grinding noise is often axle bearings, especially on 7.25's.
 
A rumbling kind of noise would be axle bearings a whine that gets higher in pitch would be in the rear .What kind of noise is it?
 
valiantwagonguy said:
A rumbling kind of noise would be axle bearings a whine that gets higher in pitch would be in the rear .What kind of noise is it?
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A whining noise as you push down on the excellorater and whines when you let off. I took it out on the highway and it seems to quiet down as you cruise. The fluid I took out of the rear today was a brownish color. Of course I don’t have the back seat in the car because I just had the top installed so it may make the rear end even louder
Pat
 
pinion bearing would make noise under acceleration or deceleration and may quiet down at cruise. Get under there and jerk on the drive shaft back there and see if there is any play at the yoke. 7.25 takes grease at the bearings, not shared with gear oil. Not sure with the 8.25. 8.25 is perfect oval, 7.25 is sort of hex shaped.
 
Rebuilt my first rear end in about 1982. This was 7.25 under a 67 slant 6 B'cuda with 86K miles on it. I had already done tune up with reman'd distributor, carb rebuild, valve adjust, etc... It ran great.
Whats next?... The rear whined like a horn blowing under load from about 40 mph up. Coasted fairly quiet. The gears did show some wear but new everything and smear pattern quietened it for the following 8 years it was our daily driver.
I put a 318 and 727 in front of it about 1986 after the slant poked the #5 rod through the block at 112K. The sad part is I put late model disc brakes and 4 LBP rallyes under it at the same time. With money spent on that 7.25 I had pretty much obligated myself to running a pair of bolt pattern adapters. Lesson learned. I wouldn't spend coins on one those rears again unless my options were as limited again. My current 67 273 B'cuda still has all its OEM running gear at 93K miles. This rear is quiet as one could wish for. Go figure. Good luck with yours
 
pishta said:
pinion bearing would make noise under acceleration or deceleration and may quiet down at cruise. Get under there and jerk on the drive shaft back there and see if there is any play at the yoke. 7.25 takes grease at the bearings, not shared with gear oil. Not sure with the 8.25. 8.25 is perfect oval, 7.25 is sort of hex shaped.
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It has to be an 8.25 because it is oval shaped I did change the the pinion seal because it was leaking. Do you know if the bearings get greased from the rear end fluid?
Pat
 
fuzzman said:
It has to be an 8.25 because it is oval shaped I did change the the pinion seal because it was leaking. Do you know if the bearings get greased from the rear end fluid?
Pat[/QUOTE I never worked on an 8.25, but on most the pinion nut has a crush sleeve under it and removing the yoke to change the seal can cause the pinion gear to lose it's setting to the ring gear.
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fuzzman said:
How would you reset that? So what your saying is that could cause it to be noisy?
Pat
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Was the rear noisey before. ? I've never rebuilt one, but years ago I destroyed an 8.75 w/3:91 gears and shortly before it went, I had done the same thing and the pinion gear was missing teeth after putting it in reverse one day. I was told that the crush sleeve will hold the pinion depth as it crushes slightly after being torqued. Someone one this site can tell you if this may be your problem
 
B'cuda said:
Was the rear noisey before. ? I've never rebuilt one, but years ago I destroyed an 8.75 w/3:91 gears and shortly before it went, I had done the same thing and the pinion gear was missing teeth after putting it in reverse one day. I was told that the crush sleeve will hold the pinion depth as it crushes slightly after being torqued. Someone one this site can tell you if this may be your problem
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If you had a way to re-torque the pinion nut to the same spec it was you may be ok, but if you torqued it more or less, and now it’s noisy, you may need to have someone set it up again.
 
My dad bought my dart new in 67. he kept notes of everything that has ever been done even washes and wax. in his notes in the first few hundred miles he noted rear end (7 1/4) noise / whine at fwy speeds same noise loaded or unloaded. The dealer rebuilt the rear and the noise was still there. For the next 20 years I recall hearing the noise and I assumed it was normal. when I inherited my dads car last year I drove it and heard the noise. I did not recall it being that noisy and I assumed after 300,000+ miles the bearings were going. Only after I started collecting parts to swap over to an 8 3/4 did I find his records from when it was new. If I had I might have just left it alone.
Hearing others with the same issue makes me think it is just a design flaw of sorts.
 
If the noise disappears or reduces significantly while cornering (either left or right), then it's likely a wheel bearing issue.
 
I just came out here in the garage and the rear is a 7.25 I don’t know if it makes a difference with the preload or not in the service manual you are supposed to use a additive the same they use for 8.75.
Pat
fuzzman said:
It has to be an 8.25 because it is oval shaped I did change the the pinion seal because it was leaking. Do you know if the bearings get greased from the rear end fluid?
Pat
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t
 
fuzzman said:
I just came out here in the garage and the rear is a 7.25 I don’t know if it makes a difference with the preload or not in the service manual you are supposed to use a additive the same they use for 8.75.
Pat

t
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Well,7 1/4 rears are a dime a dozen so before you spend a nickle on this one see what you can get as a replacement.People actually give them away !
 
@ fuzzman - Based on your noise being on accel and decel, I'd have to agree with other posters here that it is a pinion/carrier bearing issue and not an axle bearing. Because 7.25 rears do not use the crush sleeve your changing of the pinion seal is likely not the cause of noise. Agree with many posters on here that cost of "fixing" your rear end far exceeds that of finding and installing a used replacement if you stay with a 7.25 type.
 
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valiantpatrol said:
@ fuzzman - Based on your noise being on accel and decel, I'd have to agree with other posters here that it is a pinion/carrier bearing issue and not an axle bearing. Because 7.25 rears do not use the crush sleeve your changing of the pinion seal is likely not the cause of noise. Agree with many posters on here that cost of "fixing" your rear end far exceeds that of finding and installing a used replacement if you stay with a 7.25 type.
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I know you guys keep saying just find another rear for it. The problem is this car is a numbers matching car is there an easy fix to quiet this rear down. I have a 8.75 case laying around in the garage that came out of a early 60’s b body car it was mounted on my 67 when I got it. I could shorten the housing to fit an abody and by the remaining pieces I need to make it whole and go that route. But like you guys keep saying that you can pick up another 7.25 fairly cheap but who’s to say it won’t have the same issue. Thanks for all the input
Pat Faley
67 NB S Clone
69 barracuda vert
East Peoria,IL
 
Other than a date code, there are no "numbers" on a rear end they are not serialized to the Vin as engines and transmissions are. The problem of the replacement having the same issue is possible, more so if buying from stranger on Craigslist. But dealing with fellow FABO members should eliminate that. Things to check so you don't end up with the same problem on a used rear are:

1) the pinion assembly should not move in and out at all (towards/away from ring gear)
2) pinion assembly should turn freely with no binding/tight spots thru one full revolution of the ring gear ( i.e. you'd rotate the pinion 3.55 revolutions for one full ring gear revolution on a rear with a 3:55 gearset)
3) the amount of free play when turn rotating the driveshaft yoke back and forth (without rotating the ring gear) should be in the thousandths not fractions

But nothing is guaranteed, and my quick checks are far from 100% guaranteed. No right or wrong, you just have to prioritize the various factors such as cost, originality, etc. are most important to you and proceed.
 
Axle bearings are not lubed with rear ends 90w. Remember the axles have an inner seal to stop the 90w. Axle bearings are packed with wheel bearing grease. Just a side note to diagnosing rear end noise, cupped tires cause the same noise. Had a customer come in to rebuild his noisy rear end. Indeed there was a terrible rolling noise coming from the rear end. Noticed that the rear tires were cupped, so I rotated them to the front. Surprise! the noise was now in the front. The dealership was pissed that they lost the job.
 
Don’t want to hijack your thread but have a question for you guys that know rear end issues.

I’ve got an 8-3/4 center chunk with 2:76 gears that I was considering bolting in just cause I may be doing a long road trip. Anyway I’ve run this chunk before on a different car and I know it has a whine , only when decelerating. Any idea what the issue may be in that case?
 
MileHighDart said:
Don’t want to hijack your thread but have a question for you guys that know rear end issues.

I’ve got an 8-3/4 center chunk with 2:76 gears that I was considering bolting in just cause I may be doing a long road trip. Anyway I’ve run this chunk before on a different car and I know it has a whine , only when decelerating. Any idea what the issue may be in that case?
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Probably nothing to worry about.
The pattern is just off a smidge, and after it has a few thousand miles on it , it's doubtful it can be changed. It will likely whine forever
 
AJ/FormS said:
Probably nothing to worry about.
The pattern is just off a smidge, and after it has a few thousand miles on it , it's doubtful it can be changed. It will likely whine forever
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While we are on this subject I ended up getting another rear end and it is out of a 70’s dart or demand so the question is I need to change out the backing plates between the two rear ends. Mine is a 69 which should have the clips to take the axles out and the rear end that I bought the axles should have to be driven out with a puller, according to what I read.
Hopefully that is right
Pat
 
No 7.25 rear end has axle retaining "C" clips. All 8.25 rear ends do. As long as replacement rear is 5 lug x 4" wheel mounting pattern and the OD of the backing plates are the same on both rear ends you should not have to change backing plates. If backing plate OD's are different (one has 9" dia brakes and the other 10" dia.) just remove the (4) axle retaining nuts using the access hole in the axle face and tug or use puller. You do not have to open the gearcase to pull a on a 7.25 rear.
 
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