Chevrolet Suburban 3500 Questions

[Geotrash]

The tip I bought and linked to is a perfect fit. If I can’t be good, I might as well be lucky:

 

[Bigburb3500]

Took the truck on a 900 mile road trip this weekend thru NC and TN. Seems like after I added a bit of transmission fluid everything is back to normal. Temps were 168° and climbed to 174° when going uphill at 77MPH. Ambient temp 94° then trans temp would come down after leveling off/going downhill. Saw 184° during a major traffic jam/stop-go but cooled down when moving again.

@NickTransmissions - I have noticed/developed a pretty harsh 2-1 downshift. Only happens when coasting slowly to a stop. If the brake is applied then the harsh shift isn’t noticeable or doesn’t happen. Any thoughts or advise? I have a Blackbear tune, could it be a program issue?

 

[Geotrash]

Took the truck on a 900 mile road trip this weekend thru NC and TN. Seems like after I added a bit of transmission fluid everything is back to normal. Temps were 168° and climbed to 174° when going uphill at 77MPH. Ambient temp 94° then trans temp would come down after leveling off/going downhill. Saw 184° during a major traffic jam/stop-go but cooled down when moving again.

@NickTransmissions - I have noticed/developed a pretty harsh 2-1 downshift. Only happens when coasting slowly to a stop. If the brake is applied then the harsh shift isn’t noticeable or doesn’t happen. Any thoughts or advise? I have a Blackbear tune, could it be a program issue?

If it helps, both of my 6L80's and the 6L90 in the 3500 will occasionally have a sharp/firm shift from 2-1 when coasting to a stop. I haven't been able to pinpoint the exact conditions to replicate it, but it happens more often in my 2012 Yukon XL. All 3 are Blackbear tuned, but no idea if there's a correlation there. I noticed it on the 2012 after the cam swap back in 2021. It's not firm enough to be an uncomfortable jolt, but it is noticeable enough to get my attention when it happens.

 

[Bigburb3500]

If it helps, both of my 6L80's and the 6L90 in the 3500 will occasionally have a sharp/firm shift from 2-1 when coasting to a stop. I haven't been able to pinpoint the exact conditions to replicate it, but it happens more often in my 2012 Yukon XL. All 3 are Blackbear tuned, but no idea if there's a correlation there. I noticed it on the 2012 after the cam swap back in 2021. It's not firm enough to be an uncomfortable jolt, but it is noticeable enough to get my attention when it happens.

It’s more like a stumble. Almost like it wants to downshift but engaged the clutch too soon or didn’t shift quick enough, grinding a gear a bit. It’s definitely uncomfortable because it’s doesn’t sound or feel great + makes a shutter thru the truck.

 

[Geotrash]

It’s more like a stumble. Almost like it wants to downshift but engaged the clutch too soon or didn’t shift quick enough, grinding a gear a bit. It’s definitely uncomfortable because it’s doesn’t sound or feel great + makes a shutter thru the truck.

I'm not an expert here, but once thing I've seen come up repeatedly on the 6L80/90 leading to harsher shifts is PR valve wear in the valve body. Transgo makes an upgraded replacement kit for these that some say is a worthwhile investment to fix the issue and prolong the life of the torque converter and the clutch packs as well.

 

[Geotrash]

Got the diagnosis a few minutes ago from the driveline shop. Manufacturing defect. It turns out that the little wire keeper on the barrel adjuster, on the driver's side axle shaft at the carrier, was installed in the wrong direction, which allowed that adjuster to back off over time and mess up the backlash.

That eventually started making metal and took out the carrier bearings and the pinion bearing, leading to the noise(s) I was hearing. So they're going to do a full rebuild on the axle, including new ring and pinion, all new bearings including wheel/axle shaft bearings and seals. $2,800 with all parts and labor and a warranty, and that also includes installing the Bilstien 4600's I brought in with me.

I say noises plural because I was hearing a steady growl that sounded like a carrier bearing to my ear, and a higher pitched howl when I took my foot off the gas, which I surmised was a pinion bearing. Turns out I was right on both points, and the owner of the shop commended me on my hearing. Lol.

I don't like it, but it will be good to have it fixed right.

 

[swathdiver]

It turns out that the little wire keeper on the barrel adjuster, on the driver's side axle shaft at the carrier, was installed in the wrong direction, which allowed that adjuster to back off over time and mess up the backlash.

So the open ends of the keeper weren't in the holes but on the left side doing nothing?

 

[Geotrash]

So the open ends of the keeper weren't in the holes but on the left side doing nothing?

Yup, that's my understanding based on our conversation and the written estimate:

Whining noise rear diff
-found passenger side carrier
adjustment lock tab out of position.
Resulting in incorrect carrier preload
and backlash adjustment.
-recommend rear axle overhaul

 

[swathdiver]

Yup, that's my understanding based on our conversation and the written estimate:

Whining noise rear diff
-found passenger side carrier
adjustment lock tab out of position.
Resulting in incorrect carrier preload
and backlash adjustment.
-recommend rear axle overhaul

While building my 14-bolt, I would put it in backwards so as not to lose it but made sure it engaged the holes on final assembly!

Well, at least she's zero-timed and ready for decades of service at today's prices.

 

[NickTransmissions]

Took the truck on a 900 mile road trip this weekend thru NC and TN. Seems like after I added a bit of transmission fluid everything is back to normal. Temps were 168° and climbed to 174° when going uphill at 77MPH. Ambient temp 94° then trans temp would come down after leveling off/going downhill. Saw 184° during a major traffic jam/stop-go but cooled down when moving again.

@NickTransmissions - I have noticed/developed a pretty harsh 2-1 downshift. Only happens when coasting slowly to a stop. If the brake is applied then the harsh shift isn’t noticeable or doesn’t happen. Any thoughts or advise? I have a Blackbear tune, could it be a program issue?

Those temps are fine...Mine routinely gets to 200 or so in the summer...Drove it today, trans temp topped out at 205...No issues....Your harsh 2-1 downshift could be a myriad of things, including normal behavior to wear in the compensator feed circuit, pump PR valve, latent release of the 2-6 clutch regulator valve, TEHCM pressure switches and so forth.

Put a scan tool on it, see what the trans data tells you, if anything.

No on the Blackbear tune unless it started doing that immediately after the tune was uploaded.

 

[Bigburb3500]

Got the diagnosis a few minutes ago from the driveline shop. Manufacturing defect. It turns out that the little wire keeper on the barrel adjuster, on the driver's side axle shaft at the carrier, was installed in the wrong direction, which allowed that adjuster to back off over time and mess up the backlash.

View attachment 462406

That eventually started making metal and took out the carrier bearings and the pinion bearing, leading to the noise(s) I was hearing. So they're going to do a full rebuild on the axle, including new ring and pinion, all new bearings including wheel/axle shaft bearings and seals. $2,800 with all parts and labor and a warranty, and that also includes installing the Bilstien 4600's I brought in with me.

I say noises plural because I was hearing a steady growl that sounded like a carrier bearing to my ear, and a higher pitched howl when I took my foot off the gas, which I surmised was a pinion bearing. Turns out I was right on both points, and the owner of the shop commended me on my hearing. Lol.

I don't like it, but it will be good to have it fixed right.

Good ear for spending money! Glad you are getting it fixed tho.

 

[Bigburb3500]

Those temps are fine...Mine routinely gets to 200 or so in the summer...Drove it today, trans temp topped out at 205...No issues....Your harsh 2-1 downshift could be a myriad of things, including normal behavior to wear in the compensator feed circuit, pump PR valve, latent release of the 2-6 clutch regulator valve, TEHCM pressure switches and so forth.

Put a scan tool on it, see what the trans data tells you, if anything.

No on the Blackbear tune unless it started doing that immediately after the tune was uploaded.

I can’t remember if it was doing it before BB… I only had the truck a month or so before I got the tune.

I will try to get out in the next day of so. I think my readers do pretty detailed trans scans… let me see what I can find! Thank you!

 

[Bigburb3500]

I can’t remember if it was doing it before BB… I only had the truck a month or so before I got the tune.

I will try to get out in the next day of so. I think my readers do pretty detailed trans scans… let me see what I can find! Thank you!

Hello, quick question: I was using my EFI Live AutoCal reader to see what was going on with the trans to better ask questions here. I need help with 1) What specifically am I looking for when driving around? What metrics am I looking at or need to compile to get a better idea of what’s going on? 2) Is the AutoCal something I can use because it says it does trans live data but might not be ideal?

Thanks in advance!

 

[Geotrash]

Hello, quick question: I was using my EFI Live AutoCal reader to see what was going on with the trans to better ask questions here. I need help with 1) What specifically am I looking for when driving around? What metrics am I looking at or need to compile to get a better idea of what’s going on? 2) Is the AutoCal something I can use because it says it does trans live data but might not be ideal?

Thanks in advance!

I don't believe that the AutoCal software has a graphing function that would allow you to monitor multiple parameters and then overlay them to look for discrepancies or problems, but I could be wrong about that. HP Tuners does have that ability however, which is partly why I have both. Nick can tell us more, I'm sure (I'm also conscious that he gets summoned a lot here and he gives us a lot of time for free), but here are the parameters I would be watching if it were mine:

1/ The difference between commanded and actual fluid pressure readings or line pressures. It reveals whether the pump is operating properly or if there is pressure being bled off internally somewhere. Fluctuations or improper pressures can affect shift quality and clutch engagement.
2/ Input and output shaft speeds, along with engine RPM, allow for calculation of gear ratios and potential slippage.
3/ Shift Solenoid Status: Monitor for malfunctions that cause harsh or delayed shifting.
4/ Torque Converter Clutch Slip: Should ideally be close to zero when the TCC is engaged. Significant slippage can indicate TCC wear or pressure issues.
5/ Fluid temperature. High temps can indicate slippage in the clutch packs.

 

[Bigburb3500]

I don't believe that the AutoCal software has a graphing function that would allow you to monitor multiple parameters and then overlay them to look for discrepancies or problems, but I could be wrong about that. HP Tuners does have that ability however, which is partly why I have both. Nick can tell us more, I'm sure (I'm also conscious that he gets summoned a lot here and he gives us a lot of time for free), but here are the parameters I would be watching if it were mine:

1/ The difference between commanded and actual fluid pressure readings or line pressures. It reveals whether the pump is operating properly or if there is pressure being bled off internally somewhere. Fluctuations or improper pressures can affect shift quality and clutch engagement.
2/ Input and output shaft speeds, along with engine RPM, allow for calculation of gear ratios and potential slippage.
3/ Shift Solenoid Status: Monitor for malfunctions that cause harsh or delayed shifting.
4/ Torque Converter Clutch Slip: Should ideally be close to zero when the TCC is engaged. Significant slippage can indicate TCC wear or pressure issues.
5/ Fluid temperature. High temps can indicate slippage in the clutch packs.

Thank you! I really hate summoning him… I feel like he answers a lot of the same questions when reading thru the transmission threads. I do feel guilty and would drop a 6-pack off for him if I was nearby.

I don’t think this reader has the ability, I’m considering buying one of the less expensive bidirectional tools… would mean I have 3 different scanners for different reason… idk how I can rationalize that but gotta do what ya gotta do.

 

[Geotrash]

Thank you! I really hate summoning him… I feel like he answers a lot of the same questions when reading thru the transmission threads. I do feel guilty and would drop a 6-pack off for him if I was nearby.

We could always offer to Venmo him a few bucks when he helps us. I'm always happy to pay a pro for their expertise.

I don’t think this reader has the ability, I’m considering buying one of the less expensive bidirectional tools… would mean I have 3 different scanners for different reason… idk how I can rationalize that but gotta do what ya gotta do.

That can be tough too because they usually only display the data with significant limits on how many parameters you can show or overlay. Whereas with PC-based software, you usually have much more flexibility and if you want to get really crazy, you could download the raw data and use Excel or even Python scripting to parse and display it. It would be interesting to see if there are any YT videos out there on the graphing capabilities of various scan tools. Maybe I should start my own channel, lol.

 

[Geotrash]

As luck would have it, the shop called just as I was finishing that last post, and they're done with the rear diff on the Suburban. The owner of the shop said he personally did the setup of the backlash and adjustments, so he knows it's done right. Gonna go pick it up over lunch and I'll report back here on how it sounds.

 

[Bigburb3500]

We could always offer to Venmo him a few bucks when he helps us. I'm always happy to pay a pro for their expertise.


That can be tough too because they usually only display the data with significant limits on how many parameters you can show or overlay. Whereas with PC-based software, you usually have much more flexibility and if you want to get really crazy, you could download the raw data and use Excel or even Python scripting to parse and display it. It would be interesting to see if there are any YT videos out there on the graphing capabilities of various scan tools. Maybe I should start my own channel, lol.

I really should be better with computers and tech based on my age demographic, but I really have limited to no knowledge of how to mess with the vehicle files.

Maybe I get learn a new skill when I wrap up a few things I have going on lol

 

[Geotrash]

Differential is silent now. I heard a little bit of pinion/gear mesh noise when coasting for the first 3-5 miles, but it quieted down completely by the time I got home, 15 minutes later. Now the break-in process begins. I have to do the first 100 miles in 15-20 mile increments at speeds less than 55 mph, followed by a compete cool-down between trips. That's perfect for taking my wife out to dinner in the country around here.

From 100 miles to 500 miles I can go up to 65 mph, for 30-40 minutes, so that's lots of trips to Costco. No towing until the 500 mile break-in is complete, so they say. I'll comply, but it means we'll need to use one of the Yukons for a weekend camping trip coming up. Se la vie - just happy to have the problem fixed.

Oh, and I had him install a Lube Locker gasket to make future maintenance easier.

 

[Bigburb3500]

Differential is silent now. I heard a little bit of pinion/gear mesh noise when coasting for the first 3-5 miles, but it quieted down completely by the time I got home, 15 minutes later. Now the break-in process begins. I have to do the first 100 miles in 15-20 mile increments at speeds less than 55 mph, followed by a compete cool-down between trips. That's perfect for taking my wife out to dinner in the country around here.

From 100 miles to 500 miles I can go up to 65 mph, for 30-40 minutes, so that's lots of trips to Costco. No towing until the 500 mile break-in is complete, so they say. I'll comply, but it means we'll need to use one of the Yukons for a weekend camping trip coming up. Se la vie - just happy to have the problem fixed.

Oh, and I had him install a Lube Locker gasket to make future maintenance easier.

I’m interested to see what your thoughts are when you swap back into your 1/2 ton SUV. I know you saw it’s night and day but curious how big of a difference going backwards is and if you “forgot” how much more you worked the truck.