Different 3.42 axles for towing

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wdonovan

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Hi all. I need some clarification on axles for towing with a 2014 Tahoe. Tow guides say 3.42 axle for over 8000# compared to 5200# for the 3.08 axle. It seems that there are (were) 2 different axles made. One is an 8-1/2" rear and the other a 9-1/2". Both are designated GU6, which is what Chevy calls for to tow the heavier weights.

My question is - Is the ratio the determining factor? Or is it really the increased capacity of the 9-1/2" rear? I can't find any info on this. It makes much more sense to me that the size of the parts can boost towing capaciy by 3000# that simply changing the gear ratio.
 

swathdiver

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Hi all. I need some clarification on axles for towing with a 2014 Tahoe. Tow guides say 3.42 axle for over 8000# compared to 5200# for the 3.08 axle. It seems that there are (were) 2 different axles made. One is an 8-1/2" rear and the other a 9-1/2". Both are designated GU6, which is what Chevy calls for to tow the heavier weights.

My question is - Is the ratio the determining factor? Or is it really the increased capacity of the 9-1/2" rear? I can't find any info on this. It makes much more sense to me that the size of the parts can boost towing capaciy by 3000# that simply changing the gear ratio.
Simply put, the 9.5 axle was put behind RWD and 4x4 SUVs of this generation with the 6.2 engine. Your 5.3 only uses the 8.6" axle.

To answer your question, it is the gearing that determines the tow rating in this instance. Putting a 9.5 axle under your truck will make it more durable but a Tahoe is not a happy camper towing loads with high sail areas due to their shorter wheelbase.

The larger axle was used because it could handle the torque of the larger engines.
 
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wdonovan

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Thank you for the very clear answer. If I may I'd like to push this one step further.

Comparing the 3.08:1 to the 3.42:1 -
From what I read in your response, the gear ratio makes the trans gearing make more sense for the increased load. It has nothing to do with strength of components. In fact, from my Corvette hotrodding days, putting a higher ratio gearset usually came with a risk of breakage because the lower ratio had a larger pinion, shaft and possibly bearings.

That said... I towed my 8200# trailer from PA to NJ using the 3.08 gears it came with. The ride was mostly flat with only a few small hills and bridges. I am now getting ready to tow it to VA along the coast... again very flat ride. I did a lot of manual shifting during the first trip to baby the engine and transmission.

I have been under the impression that the diff was being overloaded and was looking at having the whole rear replaced. This is one single trip I need to make. In you opinion is the 3.08 safe from grenading if I baby the rig? It is a 28' travel trailer that cuts very little air compared to most rigs I see.
 

swathdiver

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Thank you for the very clear answer. If I may I'd like to push this one step further.

Comparing the 3.08:1 to the 3.42:1 -
From what I read in your response, the gear ratio makes the trans gearing make more sense for the increased load. It has nothing to do with strength of components. In fact, from my Corvette hotrodding days, putting a higher ratio gearset usually came with a risk of breakage because the lower ratio had a larger pinion, shaft and possibly bearings.

That said... I towed my 8200# trailer from PA to NJ using the 3.08 gears it came with. The ride was mostly flat with only a few small hills and bridges. I am now getting ready to tow it to VA along the coast... again very flat ride. I did a lot of manual shifting during the first trip to baby the engine and transmission.

I have been under the impression that the diff was being overloaded and was looking at having the whole rear replaced. This is one single trip I need to make. In you opinion is the 3.08 safe from grenading if I baby the rig? It is a 28' travel trailer that cuts very little air compared to most rigs I see.
You don't need to baby the rig. It is plenty strong to handle this load. The carrier for the 3.42 and lower gears is larger so if you were to regularly tow like this you would want to change the gears anyway and get the larger carrier.

Consider putting it into M5. M4 for maximum cooling. Should be a milk run on flat lands. Being a 2014, you have Cruise Grade Braking Normal Mode and Powertrain Grade Braking Normal Mode, these only work in Drive. Remember, you also have Trailer Sway Control and Hill Start Assist.
 

swathdiver

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Thank you very much. That is the answer I was hoping for.
Keep the fluids clean, run the severe service schedule and if the transmission gets up above 230 or so, change the fluid soon after the trip.

Some guys on here have put in the 2-speed transfer case and changed gears too. I've got on of those 14-bolts sitting on my work bench waiting for cooler weather to go in. Bought it for towing and drag racing. Undecided on whether to keep the 3.42 gears or go lower.
 
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