Is the 3.42 rear end good for long distance towing?

DENALIV84X4

Member
I have been told a few times it is not recommended to toe using a 3.42 rear end. Is this true? Not that I plan on towing, but I live in Central Ontario and winter can be harsh on inexperienced winter drivers and i have been known to recover locals out of ditches with truck.
 

TollKeeper

Well-Known Member
I have the same axle in my Envoy.. I am constantly pulling cars, trucks, and occasionally a semi bobtail, in the winter months. I pulled a semi out this last winter blast we had. Surprised the State Patrolman that I could do it. Rear axle lock helps... A LOT!

I dont do a lot of towing, but I also have the V8, so I have a different animal entirely. But it does pull my ATV trailer, and my Snowmobile trailer, really well.
 

DocBrown

Well-Known Member
My TB had the 3:42 rear end. I towed my 17ft travel trailer through 7% mountain grades out to Yellowstone and back. It was a little slow up those grades but it worked just fine.
 
OP
DENALIV84X4

DENALIV84X4

Member
I have the same axle in my Envoy.. I am constantly pulling cars, trucks, and occasionally a semi bobtail, in the winter months. I pulled a semi out this last winter blast we had. Surprised the State Patrolman that I could do it. Rear axle lock helps... A LOT!

I dont do a lot of towing, but I also have the V8, so I have a different animal entirely. But it does pull my ATV trailer, and my Snowmobile trailer, really well.
I have the 06 5.3 v8 with afm

My TB had the 3:42 rear end. I towed my 17ft travel trailer through 7% mountain grades out to Yellowstone and back. It was a little slow up those grades but it worked just fine.
Good to know i wont destroy the envoy if i ever pull a car out of a ditch then
 

Mooseman

Moderator
3.42 are OK, just might make the engine huff and puff a little more uphill and on takeoff but with that 5.3, you'll be fine.

One word of advice, have the AFM disabled before it fails. Multiple ways to do it; with a tune, a plug in dongle or just disconnect the electrical connector on the vacuum sensor on the brake booster (I have a thread here somewhere on that) Tune is the preferable method. Fuel savings from AFM is negligible.
 

Reprise

Lifetime VIP Supporter
Gearing comes into play mostly for ensuring the engine is at (or closer to) its sweet spot in terms of powerband. That's why higher gears (lower # numerically) are great for fuel economy (where the goal is to get to the highest gear, spinning the least RPM to do so).

You won't damage your 3.42 doing recovery for friends (especially if you're not doing it all day, every day) but you might have to rev the motor a little higher to put enough power down to pull out the stuck vehicle (and / or engage 4Low)

Really, for that purpose, it's not going to be that much difference between 3.42 and 3.73 (which would've been the only other gear you could've gotten w/ the 5.3L - and maybe not by the time your 2006 came along - I'd have to check). It's so little of a difference that it'd be a waste to find / install used diffs (you need both f/r, with 4WD) or find someone to install new 3.73s in your existing diff (assuming they'd fit in your rear carrier, especially). So keep what you got, especially if you have the locking rear diff ('G80' on the label in your glovebox (edit: see below). If you *don't* have the locker, maybe you *do* want to consider a diff / gear swap from another TB / Envoy.

Depending on how often you get called to do recovery, a winch might be a good idea (along with all of the other stuff that goes with that). With one of those, you can even potentially get yourself out of a ditch.

If you're interested in off-road and all that entails (including winching, recovery, swapping gears, etc.) -- hop on over to Offroadtb.com . Good stuff there - one of our own (no longer here, but we don't call him a 'former' member) had a hand in getting that site off the ground. Pirate4x4 is another good site for gears (but they're not GM-specific)

And as Moose mentioned while I was writing this up -- get the AFM disabled or removed. I'd be worried more about that causing damage, than your gearing, tbh.

*** on edit: You may have 'G86' instead of 'G80'. Which is still good - it's a limited slip. My Sierra has the G80 (Eaton), and I think the 360s / 370s got the G86 LSD
 
Last edited:
OP
DENALIV84X4

DENALIV84X4

Member
3.42 are OK, just might make the engine huff and puff a little more uphill and on takeoff but with that 5.3, you'll be fine.

One word of advice, have the AFM disabled before it fails. Multiple ways to do it; with a tune, a plug in dongle or just disconnect the electrical connector on the vacuum sensor on the brake booster (I have a thread here somewhere on that) Tune is the preferable method. Fuel savings from AFM is negligible.

Yes i agree the afm and fuel savings do not equate at all. How do i search the forum for your brake booster thread?
 
OP
DENALIV84X4

DENALIV84X4

Member
Gearing comes into play mostly for ensuring the engine is at (or closer to) its sweet spot in terms of powerband. That's why higher gears (lower # numerically) are great for fuel economy (where the goal is to get to the highest gear, spinning the least RPM to do so).

You won't damage your 3.42 doing recovery for friends (especially if you're not doing it all day, every day) but you might have to rev the motor a little higher to put enough power down to pull out the stuck vehicle (and / or engage 4Low)

Really, for that purpose, it's not going to be that much difference between 3.42 and 3.73 (which would've been the only other gear you could've gotten w/ the 5.3L - and maybe not by the time your 2006 came along - I'd have to check). It's so little of a difference that it'd be a waste to find / install used diffs (you need both f/r, with 4WD) or find someone to install new 3.73s in your existing diff (assuming they'd fit in your rear carrier, especially). So keep what you got, especially if you have the locking rear diff ('G80' on the label in your glovebox). If you *don't* have the locker, maybe you *do* want to consider a diff / gear swap from another TB / Envoy.

Depending on how often you get called to do recovery, a winch might be a good idea (along with all of the other stuff that goes with that). With one of those, you can even potentially get yourself out of a ditch.

If you're interested in off-road and all that entails (including winching, recovery, swapping gears, etc.) -- hop on over to Offroadtb.com . Good stuff there - one of our own (no longer here, but we don't call him a 'former' member) had a hand in getting that site off the ground. Pirate4x4 is another good site for gears (but they're not GM-specific)

And as Moose mentioned while I was writing this up -- get the AFM disabled or removed. I'd be worried more about that causing damage, than your gearing, tbh.

So good to get detailed explanations. I deleted facebook finally and came back to more appropriate social chatter, about gmt's! I will look into the site you mentioned!
 

northcreek

Well-Known Member
Just to add my experience since I had the same vehicle as you, 5.3, 342:1 and AFM. I towed a firewood trailer( 3,000 lbs.) 60 miles several times a year and never had a problem with gearing or AFM.
Traded it with 125K miles still running strong....:twocents:
 
Last edited:
OP
DENALIV84X4

DENALIV84X4

Member
3.42 are OK, just might make the engine huff and puff a little more uphill and on takeoff but with that 5.3, you'll be fine.

One word of advice, have the AFM disabled before it fails. Multiple ways to do it; with a tune, a plug in dongle or just disconnect the electrical connector on the vacuum sensor on the brake booster (I have a thread here somewhere on that) Tune is the preferable method. Fuel savings from AFM is negligible.
I could not find any detailed explanation to unplug the vacuum sensor. May be a quicj rundown here would suffice. Does disconnecting rhe vacuum sensor have any long term negative effects.
 

Mooseman

Moderator
No effects except that you will get a CEL and code for it. It's a temporary measure unless you really don't mind the light.
 
OP
DENALIV84X4

DENALIV84X4

Member
No effects except that you will get a CEL and code for it. It's a temporary measure unless you really don't mind the light.
On a quick thought, would disconnecting the vac assist on the brake booster not be really bad for the brakes... meaning id have to put mega pressure on the pedal to basically hope the suv will stop?
 

Mooseman

Moderator
Thanks @C-ya . I'm on my phone so linking stuff, for me, is a bit of a PITA.
 

BrianF

Well-Known Member
As already stated, 3.42 will work. Its not optimal by any means. Maybe more so with the 5.3 but the 4.2 is pretty anemic on the torque down low.

Now the 3.42 gears in my 3500 work just fine with the torque provided by the ISB6.7.
 

Bow_Tied

Well-Known Member
Reprise did a great job covering things.

I have the '06 5.3 w/3.42:1 axle gear ratio
I have the G80 mechanical locker. (The RPO G80 in cars usually means a limited slip differential, in trucks/SUVs it usually means mechanical locker - it's confusing that way, plus GM has used G80 for decades so things can vary over time). The mechanical locker engages through wheel speed differential left to right, well sorta. There are good Youtubes on this if you care). I believe AWD vehicles may have got the G86, not certain.

I really wanted the 3.73s when I was shopping, but choices were extremely limited. However, I think it may have been a blessing in disguise - I tow a pretty heavy RV trailer, I estimate it at around 5k loaded. The truck will not usefully stay in overdrive, the T/C unlocks constantly and trans down shifts for the slightest hill. So I don't use OD. In 3rd the engine revs higher, right in a nice RPM range for the engine to sound happy (2200-2500 depending on speed). The 3.73s in my estimation would not have been deep enough to allow OD usage so I'd be in the same place only revving 250? rpm higher on the highway worsening the 22L/100 I get towing now. The 4l60E trans has a decently low 1st gear at 3.06:1 which helps with getting rolling. The drop into second is a bit of a hit so towing I keep gassing it in 1st to avoid that.

For tow extraction - I don't think it matters. I have heard rumour towing in reverse is harder on the axle gear set so maybe minimize that, but that is not directly relevant to the gear ratio. IMO, recovery gear is the most important for effective recovery. Use a proper recovery strap and not a towing strap for one thing. Safe techniques are also hugely important. Hopefully you are experienced in this regard.
 

Mooseman

Moderator
I can attest to 3.42 and the 4.2 being a bit underpowered with my #5000 trailer having to drop to 2nd on almost all grades and 9mpg. I had to bring the Saab with the 5.3 and 3.73 out if semi-retirement and it pulls it much better.
 

Bow_Tied

Well-Known Member
I can attest to 3.42 and the 4.2 being a bit underpowered with my #5000 trailer having to drop to 2nd on almost all grades and 9mpg. I had to bring the Saab with the 5.3 and 3.73 out if semi-retirement and it pulls it much better.

Can you pull that with the Saab in O/D?
 

Mooseman

Moderator
No. Pulling any heavy load on OD is a no-no, even with 4.10 gears. Creates too much heat and constant downshifting.
 

Bow_Tied

Well-Known Member
No. Pulling any heavy load on OD is a no-no, even with 4.10 gears. Creates too much heat and constant downshifting.

Agreed, just making sure I wasn't the only one. I wish I could use OD 22+L/100km sux.
 

Brian K

Member
I installed a tranny cooler and that helps keep it much cooler. I tow a 4000 lb boat and use 3rd. no issues. Won't win any races but it gets there.
 

Online statistics

Members online
8
Guests online
305
Total visitors
313

Forum statistics

Threads
21,282
Messages
609,480
Members
15,045
Latest member
LuckyLuce

Secure Browsing

Top Bottom