Rear differential issues. Advice needed.

SteveInLA · 01-23-2019, 08:24 AM

Prerequisite info: 2010 Ford E-350. Quadvan 4WD conversion with the stock Ford rear axle. Limited slip with 4.10-1 gears option added from factory.

For a few years now I have experienced an intermittent issue that seems to be related to the rear differential. When everything is cold, creeping forward or backward with the wheels slightly turned in either direction causes a 'clunk clunk clunk' noise that appears to be coming from the rear diff and can be felt if you place your hand on the rear tire as the van is moving (slowly, of course). Harder to reproduce but more worrisome is something that only happens after driving for a few hours. If we stop completely like at the end of an offramp, then slowly accelerate with wheels turned like if we are making a right turn from a stop, there is a loud groaning noise that goes away as soon as the wheels are straight or we get above 10 mph, whichever comes first.

First, has anyone else experienced this? My mechanic claims that this is a common Ford issue and that he has a Ford truck with 250k miles that has done this all its life. He has referred me to a differential specialist and I will be taking the van to them in a few days. Quadvan has also advised repairing or replacing the rear differential. I have already changed the fluids in both differentials and added extra friction modifier. That did nothing to improve the problems.

Second, since the differential will be torn apart, I asked Quadvan if this is a good time to change the gear ratio and he advised switching to 4.30-1 gears. I have 275/70R18 tires. Based on the tiresize.com calculators, that seems to be the best choice available. Is it worth the extra expense?

Thanks in advance,
Steve

JoeH · 01-23-2019, 09:20 AM

Man that's a tough one. Just my opinion but for the expense I'd only consider changing the gearing if you were going to go to 35" or 37" tires. Or, if you towed a lot. 4.10s are a pretty good match for our vans with 33" tires.

To answer the clunking question I never experienced that with my D60 SF rear axle or the FF I replaced it with.

SteveInLA · 01-23-2019, 09:55 AM

Quote:

Originally Posted by JoeH

I'd only consider changing the gearing if you were going to go to 35" or 37" tires. Or, if you towed a lot.

Bigger tires and more towing are both things I can see in the future. After 60 mph, my speedometer is off by about 10% too.

**daveb** · 01-23-2019, 10:22 AM

Same happened to me Steve. I changed the diff fluid at a thousand miles when the van was brand new and then on a scheduled mileage maintenance program. To me it felt like it was a u-joint and could even feel it in the front end. Took a ride with SMB's drive train expert and he felt like it needed more friction modifier and they added more. It never really went away even though it was a bit tamer. Every time I did an oil change (AMSOIL HD gear oil) I had to add more friction modifier than what most suggested. At about 98,000 miles I took my van down one of the worst trails I had ever been on. Windy tight turns, crawling over rocks and trees. On my next scheduled maintenance date I got a call from my mechanic and he said I had some issues. Lots of metal in the oil. This had never happened before and looking inside there were some missing and broken bolts in the bottom of the case. One bent over bolt scored a grove in the case. Anyway he didn't want to do a full carrier replacement, so he put the cover back on, filled it with oil and I took it to a rear end shop. They couldn't believe that there was only one bolt holding the thing together. I ended up purchasing a new carrier (the case was OK). I never felt anything like what I had in the past as far as chattering during turns and to date it seems fine after about 15K put on it.

I do not know what happened for sure. Not sure if this was a Ford thing but it failed and the only thing I had done was taking it down some rough trails along with daily driving.

After switching to 315's I do wish I could have changed the ratio but tearing apart the front diff was a bit too costly at the time for me. YMMV.

JoeH · 01-23-2019, 10:23 AM

Quote:

Originally Posted by SteveInLA

Bigger tires and more towing are both things I can see in the future. After 60 mph, my speedometer is off by about 10% too.

I'm pretty happy with 35s and 4.10 gearing but I have a 6.0psd and it likes the lower rpms. Speedo is within 1% but to tell you the truth I don't remember it being off that much with 33s.

I think the formula is (desired tire size divided by factory tire size) x factory gear ratio. Generally, that put's the recommended gearing at:
33's 4.10
35's 4.30
37's 4.56

Of course that requires knowing what you had coming from the factory. Many of us don't being 2nd or 3rd owners. Not sure I'm helping any but it's also a chance to put in a Trutrac which is much nicer than the ford L/S.

TomsBeast · 01-23-2019, 10:24 AM

It sounds like classic 'locker' or 'limited slip differential' behavior to me. Most have this 'stick-slip-stick-slip-stick-slip' feel and groan sound when turning. Mine does this more after it gets warm going down the highway, then I make a sharp turn into a gas station.

A bad differential bearing will give off a constant groan, a bad ring and pinion makes more of a roar-roar-roar-roar (one roar with every rotation of the wheels). Both usually change tone and volume under power.

You can check to see if your van's locker is working, confirm you've got one, LSD, whatever by jacking up one rear wheel (leaving the other on the ground), parking brake off, trans in neutral, try to turn one tire/wheel with your foot. If it turns by foot, you have an open differential. If not, you've got some type of locker.

You could go further to be on the safe side:

Drive it down the road for 10minutes, the crawl under and feel the center section. If it's too hot to touch, stinking, or has a new leak from the pinion seal, further investigation is warranted.

DIY differential service: Drain the fluid into a clean oil drain pan, by loosening then removing the back cover. Root around inside the housing with your bare hand feeling for chunks or small pieces. Don't be alarmed if you see some 'fines' in the oil under sun or shop lght, or stuck to the magnet (if your axle has one). Obviously chunks are bad. It's also a good idea to roughly measure and note how much fluid came out. Dana 60 and Sterling 10.25 axles take 3-1/2qts.

The ring to pinion backlash in a healthy Dana 60 or Sterling 10.25 axle is .006"-.010" but I'd check your axle tag and a Ford manual to be certain. Checking backlash takes a $25 magnetic base and $30 1" dial indicator. There's plenty of youtube videos on how to perform that 10min task, cover removal is all that's required. It's one of those 'as long as I'm in here' tasks that I also do.

Most modern axles use only RTV sealant to seal up the cover from the factory, even though parts houses offer a gasket. Some mechanics use a gasket, some not. (I use RTV only) Your van should call for synthetic gear oil.

deserteagle56 · 01-23-2019, 11:02 AM

I cannot advise you as far as the noise you are hearing, no experience with that. As far as the gearing change, I can tell you my experience...
My van came from Quigley with 3.73 gears and LT275/70R17 tires. Even with the V-10 it would downshift every time it came to a hill. Even worse - I drive mainly dirt roads with it and it was constantly shifting in and out of overdrive when rolling along at 45-50 mph. Gas mileage was 12 mpg. After about 20,000 miles I got tired of the constant shifting and had a talk with the owner of one of the premier 4wd shops in Reno. His advice - go straight to 4.56 gears. Because? All these new gas engines love to rev, yet to look good on the EPA tests the factory gearing is almost always too high for anything but highway cruising.
I took the guy's advice. But I also had ARB lockers installed front and rear along with the gearing change. The gearing change made this into a whole new vehicle though. No more constant shifting in and out of overdrive, and much more responsive. Much better engine holdback going down steep hills. It's been 40,000+ miles since the gearing change and I was a bit surprised to see that my mileage still calculates out to 12 mpg. That alone tells me that the engine was struggling with the higher gearing because you'd think the mileage would have dropped with the higher rpms it now runs.

arctictraveller · 01-23-2019, 11:48 AM

I changed to 410's and feel it's a good match to my 33in tires, the speedo is very accurate. At the same time, the factory limited slip was rebuilt. I quickly experienced the stick / slip noises and tire jerking described above. It was so bad that when I was turning in a parking lot, people would look and wonder what that loud noise was coming from my van. The rebuilder told me to just add more additive, which I did. It helped for a bit, but never really cured the issue. Finally, the diff was torn apart again and the L/S rebuilt a second time. I also suspect they set it up a bit looser as I have never had a problem since. Still, I'm not too sure how effective it is any more as it may be so loose as to not transmit much power to the slipping wheel.

BrianW · 01-23-2019, 12:29 PM

My LSD made a noise like that some years back after I had the diff fluid changed by my mechanic. Turns out he didn't put enough of the friction modifier in it. I added some more and it went away. Might be worth a try at least... it's cheap and easy.

TomsBeast · 01-23-2019, 12:32 PM

Quote:

Originally Posted by arctictraveller

I quickly experienced the stick / slip noises and tire jerking described above. It was so bad that when I was turning in a parking lot, people would look and wonder what that loud noise was coming from my van...

Funny story about that: I put a Lockright locker in the back of my Suzuki Samurai. If your'e not familiar with those, they have these square teeth, springs, a built in ramp that locks both wheels together under load, allows them to 'ratchet' while going around a corner most of the time. Innovative system, compact, cheap, first one for me. Given the Sami is so light, when making a sharp turn into a parking spaces, you'd think all hell broke loose back there, as if I had one of those cordless 1/2" impact guns going off inside the differential. "This can't be right!" I thought. I didn't buy mine from them, but I'm a customer, so called one of the tech guys at Trail Tough, and he said "Yep, ka-cunk!- ka-cunk!- ka-cunk!, that's how they are, it's totally normal. Live with it unless you want to upgrade to an ARB"