rear end whine (new to me van)

[surfmore72]

this is not the same issue i posted a few weeks back...different vehicle.

I just bought a 99 chevy express 1500 conversion van 120k.  the van has a newer drive shaft that the previous owner didnt know anything about.  it didnt have plates on it so i wasnt allowed to test drive it.  he must have taken it up to 41mph during test drive..... :angel:   At 42 mph a loud whine develops from the back, at 48 it goes up an octave or two.  at 52mph it stops.  when i get off the accelerator the noise stops.  when i put it in neutral it stops.  when coasting in gear it is barley noticeable when slowing down. topped off rear diff fluid (was an inch below fill hole).  still an issue.  some fluid is coming out of (bare with me here) where the differential meets to driveshaft.  not the yoke but the seal where it enters diff.  im really handy with mechanic stuff i just have never owned a truck/van or done anything with rear differentials.  what do you guys/gals think?  is this even an issue?  ive been researching for a while now.  somewhere i heard i should try rotating the drive shaft (like its out of balance or something).  any help is appreciated.  especially budget friendly ones
thanks 
e

 

[BadSaver]

I'd suspect the rear differential. Perhaps the pinion gear bearings are going out - based on the oil leak and the fact that the drive shaft that was replaced. A bad drive shaft could have put some strain on them. If the pinion gear is meshing incorrectly with the ring gear, they will whine. Hopefully the gears are okay. Just guessing here.

 

[BadSaver]

Check pinion bearings:

 

[DannyB1954]

I would also check the universal joints. sometimes people knock some needle bearings loose putting the caps on.
most of the time they are about $10-$15 a piece, so I would just replace them. Labor shouldn't be much if you are paying a shop.

 

[TMG51]

One time I had a Toyota 4runner rear differential rust through and blow out all its oil on the interstate. Toasted the pinion bearing before I realized. Replaced the bearing, patched the diff with epoxy, filled it with oil and ran it like that. It ran fine but the rear diff would whine after that. Who knows what happened to yours to change the shaft..

 

[highdesertranger]

your rear end is going out. how long it will last would be guessing. if it has been like this for any amount of time it has done irreparable damage to the ring and pinion. on a scale of 1-10 with ten being the most difficult rebuilding a rear end ranks 10. sorry to bring all this bad news but I do know what I am talking about, https://vanlivingforum.com/Thread-rebuilding-a-GM-14bolt-rear-end . there is no doubt that lucky things happen, but just replacing the seal will not stop the noise. the ring and pinion must be reset and if it has gone past the point of no return a reset will do no good. a junk yard rear end with a warranty might be the quickest, cheapest, most dependable option. highdesertranger

 

[surfmore72]

your rear end is going out.  how long it will last would be guessing.  if it has been like this for any amount of time it has done irreparable damage to the ring and pinion. a junk yard rear end with a warranty might be the quickest,  cheapest,  most dependable option.  highdesertranger

What do you think is a price range for something like that is so I don't get taken for another ride? 
Thanks

 

[BadSaver]

Used maybe $600 (eBay price), rebuilt maybe $1200. You'll have to call around locally.

In the glove box there may be a sticker with RPO codes on it. This will indicate what rear end you have.

 

[closeanuf]

check out www.car-part.com  you can specify the part you want year make and model area of the country you are in and get a phone number of a wrecking yard to call.

 

[SternWake]

In early '08 I replaced my 8 3/8 axle with a 500$ junkyard 9 .25. It required a conversion U joint on the back end of the driveshaft to fit the pinion yoke.

When I took apart U joint, which visually appeared to be in good condition, I found the needle bearings were flattened and diagonal.

They were likely the source of the noise that made me replace the axle. About 1 month before, I had submerged the Axle crossing a stream in Baja. Had I only been wise enough to pump ithe U joint with grease son after, perhaps I could have saved a lot of bother

The 8 3/8 Axle was worn and some spider gears had some serious pitting, but it likley could have gone much longer.

My Junkyard 9.25 was noisier. I spent 7XX$ for a pro to install new bearings and reshim pinion gear. They had to straighten the housing, and painted it too.

Nice and quiet now.

My point is, is that the noise can certainly just be a U joint and not the whole diff, but the pinion seal leaking is not going to go away on its own and will just get worse.

 

[jerryg]

Nut on end of pinion shaft (behind u joint) may be loose causing seal to leak and ring and pinion to not mesh properly. Torque on nut is (guessing) 200 ft. lbs or more check specs. If loose clean threads and torque using Loctite on threads.

 

[highdesertranger]

you just can't tighten the yoke nut. the pinion bearings are preloaded to a certain spec. there is a one time use crush sleeve in there that sets the preload and the backlash. the backlash is also set with the carrier bearings. all of these settings MUST be within spec or you will have a noisy, short lived rear end. highdesertranger

 

[frater secessus]

if it's time for a new rear end this might be a good time to install one with limited slip if it didn't have it already. I think it's called G80 on the chevy/gmc units, and would show up on the sticker BadSaver mentioned.

Someone who knows more about that will chime in, if you need info on it.

 

[Gary68]

if it only happens at certain speeds then i would look at something out of balance like that new driveline

 

[TMG51]

My 4runner would also whine only at certain speeds and it was definitely the rear end.

 

[surfmore72]

I'll put it up on jack stands tomorrow and see how it feels.  From the ground the pinion is tight (nothing like that video above).  The u joint is old.  Looks original.  I'd probably want to replace it even if i end up with a new /used diff axel set up.  So a new u joint seems like a no brainer.  Looking at some videos the differential  rebuild is way beyond my skill.  What are the main complexities of a full swap?

 

[SternWake]

Full swap considerations.

The U bolts are not really supposed to be reused, it could be a real difficult removing the nuts.

The flexible brake line might be due for replacement. requires bleeding brakes.
Drum Brake's on new Axle might need some loving.

Parking brake cable might be too long or too short or not a direct swap
New Axle might have different diameter yoke than previous.
Gear ratios. I replaced a 3.55 with a 3.55. Luckily Dodge usually put a little tag on a diff cover bolt so I disregarded any axle that did not have a 3.5 stamped on the diff cover bolt.

I did not want to have to get 8 lug rims so looked for 5 lug rims, and a 5.5 x 4.5 pattern. Dodges pre 86 or something had a smaller bolt pattern, but still 5 lugs.

I got an axle from another 1996 dodge van, not sure if one from a truck would be the same regarding axle tube length and spring perches.

Probably a lot more considerations with a junkyard axle swap I have not listed

 

[GotSmart]

Dodge was great on parts being standard.  When I mounted the motor in my basket case Dodge, I removed the AT brace, and reversed it.  They made one unit that would fit all the AT options.  I sent in the old drive shaft for it to be shortened.  $110 complete.  balanced and new u~joints. 

 

[surfmore72]

So I jacked the van up.  Rear u joint has no play in it.  The whole shaft seems to spin a little before the wheel does 
Hers a video 

There is some up and down play at the tranny yoke (seems to come from the shaft going into the tranny. 

My axle assembly is flaking rust.  So I don't think rebuild is in order (but maybe) How do I go about getting a different assembly?  Don't have a good mechanic around here (somers point nj) .  Aamco?  Where do I even start? Do I have to find the rear end first and have a guy install it?  Ugh

 

[surfmore72]

Is this something the chevy dealer would do?