Hi all, so ever since I've had my rear differential rebuilt, I noticed significant engine braking especially at 60 mph. Driving on a 3 hour trip to visit my parents, it got very annoying. All new OEM GM parts were used. Here is a typical scenario for when I feel the issue: highway driving 70 mph, I left off the gas for whatever reason, you feel the car start to slow down like normal, then once the vehicle decelerates to 60 mph, you feel the significant engine braking happen. You can feel it even on slower speeds like during city driving, but those times feel normal to me. Its just the highway speeds where I feel its a bit too much.

I'm very sure this issue was not there before the rebuild, at least it wasn't this significant and noticeable. Could this be a result of an over torqued pinion bearing? what are the possible causes? I have the 4 SPD, HMD, 4L60-E trans, its a 07 Tahoe LTZ. Does anyone notice any engine braking at 60 mph like I do? I think I'll bring the car back to them and let them test drive again, but request we get on the highway this time.

Next time if any of you could pls check when you driving on the highway, get up to 70 mph and let off the gas and wait till the car hits 60 mph and see if you have a significant amount of an engine braking feel, I would appreciate it, thanks in advance!

EDIT: just got back from some more highway driving, and I notice that it can be any highway speed, but maybe 3 seconds after letting off the gas you will feel the significant engine braking. I also suspect that the 3-4 clutch pack may be worn, and I wonder if that could cause this symptom of signifcant engine braking?

I also posted a video of when it happens, you'll see im going about 66-67 mph, rpms @ ~1900, the I let off the gas, and speed drops to about 64 mph then the rpms drop about 400rpm to 1400 rpm (is this a downshift?), and I think thats when the significant engine braking happens or at least one instance of it. It will happen at faster speeds and ~3 seconds later after letting off the gas, you'll feel the engine breaking kick in.

Sorry in advance for the vid quality and the radio disney background music, lol. I swear its my daughter is in the car listening, lol.

Heres the vid:
http://vid279.photobucket.com/albums...psxqltyj6m.mp4

 

what happens is you coast down in neutral...is the problem gone?

 

that's funny you asked that, b/c I was running errands today, and was putting it in neutral, but really couldn't find a good stretch of clear road to really pay attention to the car's reactions. But from what I could tell when I did put it in neutral, you could feel that the "engine braking" wasn't as significant as if it was left in "drive", but I feel like I could tell there was still some resistance.

But like I said it was hard to say, just too many cars out on the road with me, and I didn't want to see like I was being a weirdo driver, lol. I'll report back after I drive it again and test. I also feel like at the lower speeds, <50 mph, I don't really feel the dragging. Seems like speeds > 50-55 mph is when its most noticeable.

 

Do you have any tuning done or the AFM disable?
After I installed my Range AFM disable I noticed I get a tad bit more engine brake since it does not go into V4 anymore.

 

SHOOT! Yes I did install the Range AFM disabler right before I had my rear diff. rebuilt! LOL! Let me remove and test it. I would have never thought installing that would cause it?! Do you know why it does cause it? I figure that it should act the same regardless, but then again I don't have a good understanding anything, lol. Thanks for this in2pro! I'll report back once I've driven w/o it.

 

UPDATE: In2pro was right on the money! =) I removed the Range Technology AFM Disabler on my drive to church this morning, and the significant engine braking was gone. I plugged it back in on the way home and the engine braking reared its head.

OCD level back to zero! lol! Thanks in2pro! I would have never ever thought it would be the Range device. And my faith has been restored in the transmission shop that did the rebuild, lol.

 

Thanks for the follow up , and you are welcome friend