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GKman
10-24-2009, 10:24 AM
Replace the ring and pinion in our '99 Dodge 5.9 l conversion van. Was shifting down on hills a lot pulling a 23' travel trailer and I guessed that a ratio change from 3.55 to 3.90 would make a difference. Shopping for gear sets, 2 vendors specifically noted that if the gears were to be put in a van use only OEM Chrysler because the "box" was a noise chamber. $200 vs $500 +. So of course I check around until I find a vendor with cheap after market gears that they claim will be fine in a van, RIGHT.

Very confident of our setup but really noisy at neutral throttle. I can live with it. Pulling the trailer (what I bought it for) won't have much neutral throttle time.
Good thing because I don't think that there is a cure.

Just curious what's the difference in gears to make the noise? Clearance is 0.006" and I assume at neutral throttle, every time a cylinder fires the pinion rocks through this clearance and gives the ring gear a bump. What can OEM gears do differently?

Doozer
10-24-2009, 12:03 PM
3:55 to 3.90 is not much to make a difference at all.
Having made the change, was it worth it?
It seems you could have possibly achieved a similar RPM increase with smaller tires.

--Doozer

Jim Shaper
10-24-2009, 12:26 PM
Doozer, it would take a 3" tire change to do that. You think going from a 30" to a 27" is going to be acceptable? It would look idiotic.


GK, the lash is partly to blame, the gears themselves are the other component. The smaller pinion has more angularity between teeth than the taller gears. Less tooth contact tends to equate to more noise in my experience. The larger the pinion, the more teeth are in close proximity to the ring and things tend to be quieter as there's more oil surface area to soak up the play.

I would've set the lash to the smallest you could get without binding. You do this after you set your pinion depth to get a good pattern. Typically, you need a housing spreader to get that close since the little shims won't handle beating in the thicker ones.

You did check your pattern with compound right?

Doozer
10-24-2009, 12:32 PM
As to the noise issue, BMW dealers sell a gear lube for their cars with a manual transmission that is supposed to have very small rubber ball particles in it. Theory being that it quiets meshing gears and offers the gears some protection when a driver "misses" a shift. Being BMW it is surely expensive, but a small quantity is probably needed to fill your diff, and it is specifically designed to quiet gears down. I don't know the exact name of the product, but I am sure the parts counter knows what it is.
--Doozer

Ken_Shea
10-24-2009, 12:33 PM
Have to agree with the small gear change being accomplished with tire size, however, that is not the way it should be done, GK did it the correct way, especially when pulling a heavy load, smaller tires equal decreased load carrying capacity, different handling, steering etc.

Perhaps a heavier gear oil may help or some of the Lucas Oil Stabilizer.?????

Doozer
10-24-2009, 12:47 PM
2.88 to 4.56 is a big change that will make a marked difference. But with such a small ratio change like 3.55 to 3.90, I am wondering what GKman will say as to if it accomplished what he was looking for, power wise. It is only a 360 gas engine. I have used a Chevy 350 with 4.10 gears to pull a 18,000 pound 40 foot trailer, and making it up hills on the highway was a problem. You had to get the truck going 75 at the bottom, and end up doing 45 at the top. Gas engines just lack the bottom end torque when the rpms start to drop. If the gear change worked for GKman, good. From my personal experience I have found that a change like that may have only small benefits.
--Doozer

bighammer
10-24-2009, 01:08 PM
we used to use sawdust, or ground up cork for that noise, i wouldn't it iwere you. but that BMW stuff sounds ok.

cookie

Jim Shaper
10-24-2009, 01:12 PM
I've got 3.73's right now with a 325ci (5.3L) and contemplated going to 4.10's for the 200rpm increase in rpm's so that it would reduce the load pulling my 5500# truck out of the hole off the line (empty, just driving around town). You'd be looking at roughly the same change going from 3.55's to 3.90's.

The guy didn't say he was having trouble making speed, he said the trans was hunting. Moving the power band up a little for the same road speed would do what he wants (as long as he moved it enough to get the power needed).



I ended up deciding not to do the swap due to not being able to put a locker in the IFS. My rear gears have excessive lash after 176K, so I'm going to replace them when the Detroit locker goes in there sometime next week. :D

GKman
10-24-2009, 01:34 PM
Good information, thanks. The change is almost 10%. A 4.11 would have been 16%. I pulled the 4,400 lb camper 2200 miles on a shake-down run before deciding. US 2 lane blacktops seem to have a standardized maximum grade (except on mountain climbs) that the 3.55 just wouldn't quite pull in drive (OD locked out). If the last 10 minutes over Wolf Creek Pass are in low, so be it. They have done a great job adding passing lanes on mountain roads so I not in anybody's way and had, in fact, plenty of company.

"...75 at the bottom, and end up doing 45 at the top..." that's not my idea of a problem any more. Must be getting old.

Like the sound of the snake oil from BMW or Lucas. Will look into it.

The smaller pinion, smaller contact = more noise makes sense but vendors make it sound like OEM 3.90 gears are quieter than after market. We both though the recommended setup yielded a nice, wide contact pattern on the bluing.

"I would've set the lash to the smallest you could get without binding. You do this after you set your pinion depth to get a good pattern. Typically, you need a housing spreader to get that close since the little shims won't handle beating in the thicker ones."

Fortunately on a 9.25" 12 bolt cover Chrysler, there are screw adjusters, no shims. You'd think you had gone to heaven.

Carld
10-24-2009, 01:43 PM
You may try resetting the backlash after it wears in some. That may cut the noise down.

Willy
10-24-2009, 01:49 PM
As to the noise issue, BMW dealers sell a gear lube for their cars with a manual transmission that is supposed to have very small rubber ball particles in it.

If you decide to use this be sure it is GL-5 rated as hypoid gear oil is not the same as a transmission oil. Hypoid gear oil has extreme pressure additives that transmission gear oils do not.
Haven't had the chance to look into it so heads up.

saltmine
10-24-2009, 03:00 PM
Usually the factory gears are allegedly better metal, and are superior with their precision when they are manufactured. I know I seldom had problems with gear noise when I worked at a GM dealer. Basically, setting up a set of helical cut gears is critical to get the whole face of each tooth to bear an equal load. This is aggravated when the finish of the gears is below standard, or the steel used is a cheaper grade than specified. A gear with a poor contact pattern will heat up, damaging the area of the teeth carrying excessive loading, and once the temperature reaches a point where it's no longer hardened and tempered, any vibration will be impressed into the softened, load bearing part of the teeth. Once this pattern is established, the gears are going to be noisy. They'll still work, but they will be noisy.
Sometimes it's possible to reset the pinion depth or backlash and move the contact patch into the proper position, and spread the tooth loading out over the entire face of the gear teeth. More often than not, the incorrect pattern will continue to produce noise, and eventually the noise "recording" will work it's way onto the correct gear tooth faces...Losing battle, trust me.

I'm always amazed at how few people, today, actually understand and know how to set gears properly. My younger brother actually went to a "specialty shop" and had a set of "Ford factory gears" installed in his 1935 Ford sedan (no...it's got a 9" Ford rear end in it)...I could have done it, and he could have done it, too, but he wanted to have it done "professionally". (famous last words)
The gear-set ($600 installed) lasted approximately 350 miles, before the improperly torqued pinion bearings failed, the gears developing a steadily increasing whine from the very beginning of his trip... (He did the "Route 66" trip, from Long Beach, Ca. to Chicago, Ill.) With replacement pinion bearings, he made another 250 miles, and the sound from the gears became unbearable.
A used differential was installed, and he finished the trip, returning along the northern route, back to California. The used rear-end never made a sound.
Fortunately, the "specialty shop" gave him a complete refund. Only because he had been doing business with them for almost 20 years.
You'd think he learned...When we were building the car, he purchased the rear-end assembly from a nationally known vendor, only to find it was poorly set up once we got the car into a "drivable" condition (yeah, the warranty had run out).
The rear-end was always a bit noisy from "day one".....After this last fiasco, we decided to take a closer look at the original third member housing. What we discovered was the pinion center-line was not perpendicular to the ring gear center-line....The ring & pinion meshed at 88.1 degrees, instead of 90 degrees. Once we discovered this little tidbit, the original third member was tossed into the junkpile. Sometimes it's a good idea to check everything.
Remember when you assume something is OK, you make "an A** out of you and me"....

Carld
10-24-2009, 03:13 PM
Having been a diesel mechanic, foreman, instructor and warranty admin. with Cummins distributors and dealers I know quite well not everyone knows what the hell their doing. Knowing from experience the PRO's aren't always pro's but always think they are.

The problem is the average person doesn't know how to tell the difference. It's easy for me to hear the bull**** but most people would think they are spouting great truths.

I do all my own work, mechanical and machining unless I am not so equipped and then I shop carefully for someone to do it.

GKman
10-24-2009, 04:01 PM
Ah ha! 3.90, 3.92, tomato, tomaato? Not same.
OEM's are 3.92 so must be 12/46 gears
Cheap after market that I used is 3.90 with 10/39 gears. Coarse teeth = big noise.

Jim Shaper
10-24-2009, 04:18 PM
Prusian blue, or dykem?

I never would've thought to use that instead. I've even used crisco, but never dye or bluing paste.

gnm109
10-24-2009, 04:36 PM
The 1960's Lincolns with the Spicer rear axle were noted for noisy ring and pinion gears. I had a 1963 that was rather noticeable since the rest of the vehicle was very quiet.

It was long out of warranty but I went to the local Lincoln dealer and spoke to the gnarled old mechanic in the back room to get the inside info on them. He told me that it was quite common to have a noisy rear end in a Lincoln and he fixed them with STP.

His method was to drain the rear end and remove the rear cover. (Spicers had the metal cover over the back portion of the unit.) Then he would put two (I said two) cans of STP on the rear cap and, using a new gasket, slap it back on and tighten the bolts. Then, he would fill the rear end to the proper level with the normal 90wt gear lube through the filler hole.

I got a gasket at the dealer and bought a couple of cans of STP on the way home and tried it. Darned if it didn't get rid of all of the noise. That STP is good stuff! Too bad they don't have those gnarled old mechanics working around in the back room anymore to give you free advice. LOL.

.

Falcon67
10-26-2009, 12:53 PM
I think your main problem is that cheap gears = noise. I don't buy off brand gears from Summit or Jegs and despecially don't use any no-name stuff. I spend the extra and use Richmond and have yet to have problems. I do my own setups in the drag cars (9" Ford) and so far no problems. We beat the sand out of two cars at the drag strip (400~500 passes per car per season) and neither rear makes much noise even with the 4.56 ratios in each. I use the recommended bearing preload and use a solid pinion spacer (not a crush sleeve), shoot for the middle backlash, get the pattern right. For lube, I use 75w-90 high pressure synthetic Valvoline. I know several that do rears professionally for racers and most will send you away if you show up with anything but a brand name gear set. Otherwise the "warranty" ends at the shop door.

coollx
10-26-2009, 01:22 PM
Based on my personal experience changing out a fair number of ring and pinions in street cars, tow vehicles and race cars, Falcon67 is 100% correct.

medwards
10-26-2009, 01:40 PM
Good r&p sets are setup are lapped together at the mfg. When you install them, you want to get as close to their setup as possible. Their setup numbers are usually marked on the gears. The further you are away from thier setup, the noiser the gears will be. If you set them up wrong and put enough miles on them to break them in (lap a new surface), there is no going back and your stuck with a noisy gear set.

.006" backlash should be fine. Where was the pattern concentrated on the gear teeth? Noise during accel or decel is usually from the pinion running off the ege of the ring gear teeth or vise versa. Noise under no load is not that uncommon for high ratio gears. The higher the ratio, the smaller the pinion gear. The smaller the pinion, the more rotation in the driveshaft for a given amount of backlash in the gears. The rotation somehow creates more driveline vibration from what I understand.

I almost always buy Yukon Premium gears. They typically source the OEM for their gear sets.

saltmine
10-26-2009, 02:41 PM
True, quality gearsets are set up and factory run, and lapped to perform properly and deliver long life. But, I've seen cheapo gears that are so crudely finished that you wonder sometimes if the ring and pinion gears are from the same set. Not to be beating up on the Chinese, but they have a habit of taking something that works, and copying it. This works...sometimes. If they don't get the grade of steel right, or the dimensions correct, they could give a rat's a**, 'cause they're wayyy over there across the Pacific Ocean.

I would be conserned about OEM Chrysler parts. Ever since their unholy marriage with Daimler-Benz, quality control as been slipping...Not only on Chrysler products, but Daimler-Benz stuff, too. And now that FIAT has their lunch-hooks in the pie, along with the UAW, they're a pretty scary bunch to deal with.. I think the only thing they got from Daimler-Benz was higher prices. And Benz only discovered they were expending too much energy making good cars, and decided to sit back and slide along on their reputation for a while. Unholy marriage.

Using two cans of STP in a differential would eventually be disasterous. The tapered roller bearings are designed to run a a specific weight of oil, and STP is well known as a "Viscosity index improver"....Make the gear oil too thick, and it won't be able to get into the load bearing surfaces in the roller bearings. Lack of lubrication= bearing failure.

We had the same, or similar problem when the Sherff's department first got their overhead cam 4.6L Fords. The shop serviced them, and added fresh 15W40 wt motor oil. The engines promptly suffered cam chain tensioner and bearing failures due to the oil being too heavy to lubricate everything properly. We switched back to 5W30 and the problems ended.