Transmission whine

[Kelpiesgmc]

Just had a great little trip in the coach with the newly broken in S&J engine. It had been a long time since I had the coach on the highway. I remember the transmission being kinda loud, but I think it's gotten louder. At around 45mph and above it almost whistles or hums whenever gas is applied. Sound instantly stops when coasting. Should I be concerned?

I checked the fluid and it looked to be correct. It shifts through all the gears like a dream.

 

[pvfjr]

Could it be the final drive? It kinda depends on the pitch of it. I'd check that oil level as well. I added a drain plug on mine so it's easy to let a little oil out check for shavings with a magnetic plug.

 

[Kelpiesgmc]

I dropped the tanks and did some other work on it so it has been a while since I last drove it. Anyway finally got around to looking into this and driving it around again.

The final drive oil was quite low. I put about 1 1/4 bottles in it and that topped it off. It still whines quite a bit starting around 40 MPH. It's screaming by 60 MPH. Sound disappears the moment I take my foot off the gas.

Maybe I should pop the cover off and have a look.

 

[LQQKatJon]

I dropped the tanks and did some other work on it so it has been a while since I last drove it. Anyway finally got around to looking into this and driving it around again.

The final drive oil was quite low. I put about 1 1/4 bottles in it and that topped it off. It still whines quite a bit starting around 40 MPH. It's screaming by 60 MPH. Sound disappears the moment I take my foot off the gas.

Maybe I should pop the cover off and have a look.

My bet would be final drive noise.

Ia it original gearing? You can find used final drives with the original 3.07 pretty easy. Getting one from a car is a good bet.

But a new ratio is always a big upgrade.

Taking the cover off. May or may not indicate a problem. It has to be drastic.

But a failure in a final drive can be catastrophic. I have seen where a final drive bearing goes out and rips off the front of the tranny on a could of coach’s.

 

[tmsnyder]

I dropped the tanks and did some other work on it so it has been a while since I last drove it. Anyway finally got around to looking into this and driving it around again.

The final drive oil was quite low. I put about 1 1/4 bottles in it and that topped it off. It still whines quite a bit starting around 40 MPH. It's screaming by 60 MPH. Sound disappears the moment I take my foot off the gas.

Maybe I should pop the cover off and have a look.

It doesn't take much more oil than that. Sounds like you ran it dry for a while, the damage may be done.

Let me know if you need a 3.07 final drive, I have several planned to drop off with Jeff I in Atlanta to build into 3.70s and LSD but he won't miss it.

 

[Kelpiesgmc]

It doesn't take much more oil than that. Sounds like you ran it dry for a while, the damage may be done.

Let me know if you need a 3.07 final drive, I have several planned to drop off with Jeff I in Atlanta to build into 3.70s and LSD but he won't miss it.

Looks like you're in the north east, it would probably cost a pretty penny to ship one down to southern Arizona?

 

[tmsnyder]

Looks like you're in the north east, it would probably cost a pretty penny to ship one down to southern Arizona?

Yes, Buffalo NY as indicated on my signature.

I'd be willing to strap it onto a pallet and drop it off at a local depot for you if you arrange the shipping.

 

[pvfjr]

I shipped a final drive from Oregon to Georgia for $160 using Pirate Ship, with an extra gearset included.

 

[tmsnyder]

I shipped a final drive from Oregon to Georgia for $160 using Pirate Ship, with an extra gearset included.

I'll check that out b/c best I could find on freightquote.com was $280 through FedEx. When I tried FedEx myself with no account, it was almost $1000.

Wow, PirateShip has a quote for UPS, Buffalo to Tucson, for $135!

 

[pvfjr]

Wow, PirateShip has a quote for UPS, Buffalo to Tucson, for $135!

Wow, that's pretty good!

 

[Carl Stouffer]

Sounds like it was run low on lubricant and the bearings, and maybe the gears are worn out. This would be a good opportunity to upgrade to a lower geared final drive. I recommend a 3.70 for Western states driving. upgrade to a limited slip if you ever drive in dirt. Pricey, but well worth the cost overall.

 

[pvfjr]

Sounds like it was run low on lubricant and the bearings, and maybe the gears are worn out. This would be a good opportunity to upgrade to a lower geared final drive. I recommend a 3.70 for Western states driving. upgrade to a limited slip if you ever drive in dirt. Pricey, but well worth the cost overall.

That's why mine went to Georgia and back. I sent them to Jeff Ianitello for his LSD and installation of a set of 3.70 gears.

 

[Kelpiesgmc]

Sounds like it was run low on lubricant and the bearings, and maybe the gears are worn out. This would be a good opportunity to upgrade to a lower geared final drive. I recommend a 3.70 for Western states driving. upgrade to a limited slip if you ever drive in dirt. Pricey, but well worth the cost overall.

Would love to— and under normal circumstances I would. But I just got laid off from my job and funds are very tight. I have a really important trip in the middle of June that I need the coach ready for. It's all very unfortunate timing.
Plan now is to use the donor tmsnyder is shipping me. I'm very grateful to have the donor given my circumstances.

 

[Kelpiesgmc]

Update:
I finally got the donor final drive installed. It is silent! I've never heard my GMC's engine on the highway like this before! It's very nice

Installing it wasn't too difficult, save for lifting it up into place. I really don't know how other people do it. I welded a little "cradle" that fits on where the diff cover bolts on and welded that to a floor jack. With that setup it was pretty painless to get it into position. I reckon it would have been nearly impossible to balance it on the jack in the correct orientation.

Here's a dumb question for y'all. My transmission dipstick is throwing me a bit: it has two stamped pits/bumps to show the level. When I check the level, I pull the stick out and wipe it clean , then reinsert all the way and remove again. On the "top" side the level is very hard to see. There is a thin film of fluid a good way up the stick. On the "bottom" side, where the two stamped impressions are pits, the fluid does not fill the pits. My impulse is to keep adding fluid until both pits are filled with fluid. Or is it full when the "bump" side of the stick has some indication of fluid up to the second bump?

I'm checking when the transmission hot., in park, on the level.

 

[Kelpiesgmc]

It turns out to be VERY important that the FD can spin because it won't fit if you lift straight up— you'll hit the steering linkage. You have to clock a little this way, and that, as you lift up.

 

[Richard RV]

My impulse is to keep adding fluid until both pits are filled with fluid. Or is it full when the "bump" side of the stick has some indication of fluid up to the second bump?

I'm checking when the transmission hot., in park, on the level.

Larry posted a good write up on how to definitively check ATF level and marking the dipstick.
https://www.gmcmotorhome.org/threads/transmission-dipstick-reading.2196/

 

[Carl Stouffer]

Update:
I finally got the donor final drive installed. It is silent! I've never heard my GMC's engine on the highway like this before! It's very nice

Installing it wasn't too difficult, save for lifting it up into place. I really don't know how other people do it. I welded a little "cradle" that fits on where the diff cover bolts on and welded that to a floor jack. With that setup it was pretty painless to get it into position. I reckon it would have been nearly impossible to balance it on the jack in the correct orientation.

Here's a dumb question for y'all. My transmission dipstick is throwing me a bit: it has two stamped pits/bumps to show the level. When I check the level, I pull the stick out and wipe it clean , then reinsert all the way and remove again. On the "top" side the level is very hard to see. There is a thin film of fluid a good way up the stick. On the "bottom" side, where the two stamped impressions are pits, the fluid does not fill the pits. My impulse is to keep adding fluid until both pits are filled with fluid. Or is it full when the "bump" side of the stick has some indication of fluid up to the second bump?

I'm checking when the transmission hot., in park, on the level.

The transmission dipstick is hard to read, especially when the fluid is hot, due to it being so thin. There is a procedure for calibrating the dipstick. It involves removing the vacuum modulator from the right side of the transmission and adding/draining fluid until it comes out of the resulting hole.

There is really no reason to do this with the transmission at operating temperature because all you are doing is setting the level on the dipstick. When the fluid level is at the bottom of the hole, it is supposedly at the correct level and you can mark the dipstick accordingly.

 

[Richard RV]

The transmission dipstick is hard to read, especially when the fluid is hot, due to it being so thin. There is a procedure for calibrating the dipstick. It involves removing the vacuum modulator from the right side of the transmission and adding/draining fluid until it comes out of the resulting hole.

There is really no reason to do this with the transmission at operating temperature because all you are doing is setting the level on the dipstick. When the fluid level is at the bottom of the hole, it is supposedly at the correct level and you can mark the dipstick accordingly.

Carl, the torque converter drains down after stopping and as the transmission cools down. If the modulator is pulled while the engine is cold the ATF level is going to be low when at operating temperature.

Ken Burton's post from the same thread I posted above;

Post in thread 'Transmission Dipstick Reading'
https://www.gmcmotorhome.org/threads/transmission-dipstick-reading.2196/post-19930

 

[Carl Stouffer]

Carl, the torque converter drains down after stopping and as the transmission cools down. If the modulator is pulled while the engine is cold the ATF level is going to be low when at operating temperature.

Ken Burton's post from the same thread I posted above;

Post in thread 'Transmission Dipstick Reading'
https://www.gmcmotorhome.org/threads/transmission-dipstick-reading.2196/post-19930

That's true. But if you are using this procedure ONLY to calibrate the dipstick, it makes no difference what temperature the fluid is when you do it. After establishing where the fluid level is supposed to be on the dipstick, THEN you can start up the engine, warm things up, and check the level with the newly calibrated dipstick in order to fill it to the proper level.

 

[LQQKatJon]

My final drive jack tool. Mine can be used on 3.07 and also 3.21. Kinda crude but it works well and have installed 6+ finals with it.