Torque management question

[TheFuzz]

I agree with Dave...something sounds off.

What year and mileage is your truck? Even in first gear without a low range, it might struggle to move with that gear ratio but once it's up and going, it should go.

 

[jkomlos]

2012 Tahoe. 40K miles. I have an appointment scheduled with the service techs tomorrow.

 

[pmexpert]

C'mon, there is no chance to pull a boat with 3.08 gearset. This ratio is fine for regular cars not trucks. Yes, it is good for fuel consuption, but not for the efficiency. You better switch to 3.73 gearset to have better results

 

[tights24]

C'mon, there is no chance to pull a boat with 3.08 gearset. This ratio is fine for regular cars not trucks.

That's the silliest thing I've heard in a long time. It's not the gears that are the problem. Something else is wrong in the transmission. I had 2.94's in my Titan and it pulled things out of the water just fine. On top of that it towed 7000lbs without issue. Even the "big tow" option in the titan was only 3.36's and they are rated for 9500lbs. I see two things causing the problem:

1. The boat is too big for the truck regardless of what gear it has in it.
2. There is something wrong with the trans.

Yes, these trucks are underpowered on torque, but not enough to not be able to pull a boat out of the water unless one of the two things above is happening. Just my opinion is all.

 

[carshius]

I don't think the rear end ratio is the issue. We are all used to having a 3.73 or even a 4.10 rear end ratio in our trucks, but with the late model 6 speed transmissions these aren't necessary. I believe the 1st gear ratio in the 4 speed is a 3.** where the 6 speed 1st gear ratio is 4.**. So that basically negates the fact that we lost the deeper rear end ratio. I've had a 2006 Avalanche with a 5.3 4L60E and a 4.10, then a 2008 Tahoe with a 5.3 4L60E and 3.73 and now a 2012 Yukon with a 5.3 with the 6L80 and a 3.08. When we bought the '12 I was reluctant because of the rear end ratio, knowing I still plan on towing once in a while but after driving it I knew for sure that the trans was making up for it.


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[NaomiSays]

You may have a mechanical problem but to answer your question yes there is throttle and power management in every area of operation, especially in first gear.

 

[pmexpert]

That's the silliest thing I've heard in a long time. It's not the gears that are the problem. Something else is wrong in the transmission. I had 2.94's in my Titan and it pulled things out of the water just fine. On top of that it towed 7000lbs without issue. Even the "big tow" option in the titan was only 3.36's and they are rated for 9500lbs. I see two things causing the problem:

1. The boat is too big for the truck regardless of what gear it has in it.
2. There is something wrong with the trans.

Yes, these trucks are underpowered on torque, but not enough to not be able to pull a boat out of the water unless one of the two things above is happening. Just my opinion is all.

Why you comparing gear ratio with Titan? It has another tranny gear ratios also))

 

[tights24]

Why you comparing gear ratio with Titan? It has another tranny gear ratios also))

I realize that but in a nutshell, and I'm not trying to start an argument mind you, gears are gears. That truck has more then enough to pull a boat out of water unless something else is wrong. Besides that, my Titan was a 5 speed and I'm assuming the OP has a 6 speed.

As Naomisays, there is also a lot of torque mgmt is the lower gears to give GM the ability to offer such a long warranty.

 

[cjweb11]

I agree with Carshius, you need to look at the diff ratio multiplied by the trans gear ratio to get a final drive ratio. the 3.08 shouldnt have a problem because the 6spd trans provides an adaquate final drive ratio for the job. Actually the final drive ratio is larger for the 6spd-3.08 than the 4spd-3.73.

6 speed w/3.08 ratio
1st: 4.02 x 3.08 = 12.38
2nd: 2.36 x 3.08 = 7.27
3rd: 1.53 x 3.08 = 4.71
4th: 1.15 x 3.08 = 3.54
5th: 0.85 x 3.08 = 2.62
6th: 0.67 x 3.08 = 2.06

6 speed w/3.42 ratio
1st: 4.02 x 3.42 = 13.74
2nd: 2.36 x 3.42 = 8.07
3rd: 1.53 x 3.42 = 5.23
4th: 1.15 x 3.42 = 3.93
5th: 0.85 x 3.42 = 2.91
6th: 0.76 x 3.42 = 2.60

4 speed w/3.73
1st: 3.06 x 3.73 = 11.41
2nd: 1.75 x 3.73 = 6.52
3rd: 1.00 x 3.73 = 3.73
4th: 0.70 x 3.73 = 2.62

4 speed w/3.42
1st: 3.06 x 3.42 = 10.46
2nd: 1.75 x 3.42 = 5.99
3rd: 1.00 x 3.42 = 3.42
4th: 0.70 x 3.42 = 2.39

Sounds like a mechanical issue or that boat is friggin' huge

 

[jkomlos]

Took the chevy tech for a ride. We are pretty sure that the TM is throttling it all back. Not sure if I am ready to void the warranty and get it chipped to remove some of the TM.

The boat isn't that big and I notice it even when towing a smaller trailer (maybe 3000 lbs max). I'm pretty disappointed at how dialed back this seems to be. It must really be retarding the timing and keeping the throttle body closed. The boat was probably 4500 lbs with trailer. Not enough to make it that hard to come out of the water. I used to own a boat dealership and have had a lot of chevy's over the years (4 tahoes, 2500 HD silverado, avalanche, and a ford excursion with the 7.3 TD). This one is by far the "softest" truck I have ever owned. I knew it wouldn't pull as well as the others, but I didn't expect this.

---------- Post added at 11:18 AM ---------- Previous post was at 11:13 AM ----------

It is the hole shot I am most concerned with. Once we get moving, it seems to be fine.