KRB

I've had a noise (well ok, many but...) that is relatively new but maybe getting slowly worse. I at first thought it was the 4" exhaust transmitting through the tranny & 4X4 shifter.

I think I now have it narrowed down to the transmission. When I shift into neutral the noise goes away or at least decreases enough that these old ears can't hear it. It seems to decrease when I shift out of OD too maybe? Hard to tell with all the other noises. Hubs locked or unlocked makes no difference.

It sounds to me like a whir/whine or like an old straight cut gear transmission sounds maybe.

Truck performs fine with about 200,000 miles. Temps are normal. Transfer case is still full of 90W. U-joints appear fine and get greased regularly. Transmission fluid looks and smells ok but does have some miles on it. Been meaning to change it for a while. Not dropped the pan yet to check for what might be floating in there but that is next on the list along with band adjustment and new fluid because that is needed anyway. And a new rooster comb but I digress.

Just curious if anybody has an idea. I have a 500 mile round trip coming up and trying to get prepared. I know we seem to spend a lot of time on here chasing down others noises...

Thanks,

j_martin

In the OD (tail shaft) there's a radial bearing that's asked to handle 1000 lbs or so of thrust for the OD clutches. When mine went, I detected a whine for less than 100 miles, then it destructed enough to take out the tail shaft housing.

Should be detectable metal in the fluid if that bearing is beginning to spall.

KRB

Ugg. I've put several hundreds of loaded miles on it so far, tempting faith as always.

I checked this morning and I think I still have the noise with OD off, it is just less discernable with the higher rpms and other extranious noises.

I'll drain asap and check for solids and report back.

Thanks

bigragu

KRB- contact Blackstone Labs @ (260)744-2380, and have them send you a test kit. When you drain your old fluid, save about half a quart, and when the test kit arrives send them a sample. It costs $28 for an analysis to be done, and they will be able to detect any out of the ordinary going ons in your tranny. There is no cost for the test kits to be shipped. I always ask for four at a time. You send a check to them when you send in your sample.

saggonwaggon91

Didnt some of the A518s And 47RHs have straight cut gears in them???

KRB

Good idea bigragu. I did an engine oil analysis many moons ago, should do both again.

j martin- when yours blew, did it drop the drive shaft? Does the OD tail shaft separate from the tranny while leaving the trans in the truck?

I'm done with the truck now so it is safe at home. I'll dig into it this weekend and see what I can determine.

I'm running Amsoil right now because at the time it was the only synthetic and when I got the truck that was what I converted everything over to (synthetics, not Amsoil ). Anybody have a better suggestion these days?

bigragu

I've been running Valvoline ATF+4 for years, and no problems, knock on wood.

KRB- have you went ahead and diagnosed the flexplate? Are you still on the original one? Seems, most everyone that has owned an automatic firstGen has had theirs replaced at one time or another. Twice for me. The first time, when it shredded, it would make a metallic noise, like a rock tumbler with marbles, only metallic. Would go away in neutral or idle. Once at low speed the sound came upon.
The second flexplate was only replaced, because the entire backside of it was scuffed up bad, from being pulled forward towards the engine and scuffing up against the engine to transmission adapter plate. Again, a metallic noise, except more of a grinding, and heard from idle on up. That was the result of my crankshaft thrust bearing busting inside, allowing the crank to slip forward. Let's hope it's not that.
Yeah, if you do an analysis, do one for the oil and one for the ATF. $56 will tell you if you have metals in those fluids from failures.

KRB

I run Valvoline in the Cummins so thanks I'll try that in the tranny.

I got the truck about 15 years ago with 90K and have not done anything to the trans other than filters and fluid and band adjustments. No idea what the PO did or didn't do.

I've read about flexplate issues. Can I check it from below? 727s have a plate at the bottom, can't remember if the 518 does?

Wife's '96 Camry has a miss (ok several), oldest daughter's '08 Sentra has a cv joint clunk (leaving Sunday to head back to school) and my farm truck/wood hauler (1977 M880) transmission is out (no reverse). When it rains it pours. At least my 1990 Corolla wagon is still chugging and my youngest's first gen RAV4 runs like a top at 210K. But they won't get my eldest moved at the end of the month. So got to get the CTD diagnosed and fixed.

I'll let yall know what I find out this weekend...

Many thanks,

bigragu

You can pull the inspection plate off, and take a look see with a flashlight and possibly a mirror for cracks. Prying on the plate towards the torque converter may bring out some snap, crackle and pop noises, if the flexplate if cracked. Try and look closely at the bolt pattern at the center of the plate, cause that's where they crack.

deere country

The overdrive section is removable in the truck without pulling the transmission out all together. It's easy to remove but doesn't just slap together to reinstall it once removed.

It's not very often you can successfully repair just the overdrive section as people usually drive them until they quit working and by that time it's sent enough shrapnel into the trans to wreck most of the seals and likley a few other things as well.

Jim5870

Overdrive units fail sometimes. See this thread for an example....

https://www.dieseltruckresource.com/...e-pics-319838/

KRB

The Valvoline 4 will be in in the morning.

I'll drain and send off a sample, check the flex plate and go from there.

Thanks all,

j_martin

Got real noisy. The bearing apparently locked up and spun in the housing, wrecking it. It didn't damage the shaft at all.

I believe the OD unit can be removed and serviced when it's in the truck Full instructions are in the MSM, but I haven't read them lately. It takes special tools to safely disassemble and assemble the OD unit due to the strong spring in the assembly.

Here's what the bearing looked like. Metal debris contaminated the entire transmission and transmission cooling system. Cleaning that up was a major task.

j_martin

Of interest. The stock OD gears are supposed to be straight cut as the beveled gears put a thrust load on things. The extra noise is insignificant compared to a normal 6BT engine. The bevel gears will work in a pinch, but are considered a weakening of the transmission.

I worried about the stock flex plate. The transmission man said it looks good. When I had a chance I bought a used SFI flex plate and put it behind the driver's seat. When the flex plate let go, DW was driving it. I give her a rough time about the lead foot, but it can't possibly be heavier than mine.

Here's another nightmare image for you: Sorry

KRB

Geez, thanks for cheering me up...

Drained/pumped the fluid out. To my surprise not many sparklies in the pan and some grey sludge but just a bit. More brown than what the dipstick indicated.

Looked it up and I'm embarressed to admit but it has been 10 years since I changed the tranny fluid... Reap what you sow...

Got some Valvoline ATF 4 but barely. NAPA didn't have enough in stock and although I get a discount there I wanted it now so went to O'Reilys. I knew I had made a mistake when I asked for Valvoline ATF 4 and he gave me a case of O'Reilys ATF 4. When I told him I wanted Valvoline he said ok but what brand then? Should have gone back to NAPA and just waited...