Suburban towing a Suburban

[j91z28d1]

just to throw in the 2 cents of what I read here about towing and transmissions that makes sense to me. the resident transmission guy say it's best for your tranny to tow in the gear that's 1:1 or as close as you have. I guess the 6l80 doesn't have 1 to 1. but if you tow in 4th gear I believe it was, which guys do that pull big wind brake trailers all around the country well over the owners manual recommended weight, with specific hitches and stuff.

I tend to listen to what the guys successfully do over the theory a bit. I agree in theory that if you do the math and end up at the same rpm in 6th gear as you have in 4th gear the engine will tow better in 6th than it did with the 3.08 in 6th. but 6th is a double over drive, that's asking a lot of what's probably the smallest gear set and clutchs in it. Will it blow up? I don't know, I'm not a tranny guy. we'll I'm a manual tranny guy. I don't go inside autos, but even a manual you tow in 1:1


as for the gears, I can tell you from years of drag racing, a high gear is very much weaker than a lower gear, every step is one less tooth that much smaller pinion and it's spinning that much faster making heat. i personally would leave the 3.08 and tow in 4th gear. unless you can't get it moving in 1st well enough, then a gear will help you. putting 4.10s in it and taking off in 2nd all the time because 1st is pointless is kinda blah.


also tow ratings in general are rear end size limited. the bigger 14bolt had a higher tow rating in most cases.. the tongue weight seems to be all in hitch setup, trailer brakes will handle most of the brake worries. you're left with rear end limits, oil and transmission cooling.


as far as gas mileage goes, and theirs entire forums on hypermiling that I've spent to much time reading, a petrol engine is most efficient when its being worked... not over worked so that it needs richer a/f to survive but not under worked either. you need load it decently at the lowest rpm it's happy at for the best fuel usage.

 

[Marky Dissod]

... resident transmission guy say it's best for your tranny to tow in the gear that's 1:1 or as close as you have.

Wholeheartedly agree with this. With 6L80, that's 4th.

as for the gears, I can tell you from years of drag racing, a high gear is very much weaker than a lower gear, every step is one less tooth that much smaller pinion and it's spinning that much faster making heat.
i personally would leave 3.08 and tow in 4th, unless you can't get it moving in 1st well enough, then a gear will help you.
putting 4.10 in it and taking off in 2nd all the time because 1st is pointless is kinda blah.

For GMT900s, 3.73 is the tow pack gear for 6L80E pickup trucks. (4.10 with 6L90E was for 2500 stuff, and came with larger axles.)
If that's too much gear (no hills to worry about?), 3.42 is the tow pack gear for 6L80E suvs.

tow ratings in general are rear end size limited. the bigger 14bolt had a higher tow rating in most cases.

When given the SAME rear end & axle housing - say, GM 8.625" 10-bolt? -
3.73 has a higher tow rating than 3.42, 3.42 has a higher tow rating than 3.23, etc.

so far as gas MpG goes, and there's entire forums on hypermiling that I've spent too much time reading, a petrol engine is most efficient when its being worked.
not overworked so that it needs richer a/f to survive, but not under worked either.

Hypermiling is NOT towing / hauling. Towing with 3.08 instead of 3.42, is sacrificing transmission durability for MpG.

 

[j91z28d1]

I have 3.08s in mine, my 4th is 1:1 and cruising with just a car on a car trailer was uncomfortably high rpm and felt pointless. after a few hours a gave up and let it use it's overdrive. I can't imagine anyone actually screaming down the road in 4th gear at 3.73s or more. of course this was flat i10. I'm sure mountains would he different, but I'm still shifting at some point. turns out later I found later luckily my tranny doesn't have actual over drive gear or clutches to worry about. it's just, electric motors spinning a planetary to change the ratio, so it's not so bad on it I guess, as long as it all stays cool.



how much different are the tow ratings for different gears in the same size smaller housing? few 100lbs? I feel like there might be more to it like coolers and brakes added to that option code than just a little different rear gear?
I don't think they put 3.08 in a 14bolt right? I only briefly looked incase my 10 bolt went out and needed a used one, might as well upgrade.

back in 08 the caddy version of mine had a 3.42, but after towing what I tow, just a corvette on a car trailer, it's bearly over the tow rating, and so far just flat land. I wouldn't go up on mine. it just wouldn't make sense to me.




as for MPG I was thinking about when not towing. you need to work the motor a bit to get mileage out of it, that's why I believe gm locks and unlocks the converter so much stock. keep those rpms as low as possible but they just didn't put a clutch in the converter that could handle it. MPG while towing it's probably a whole different world I've never gotten into. gas engines and tow fuel mileage doesn't seem to be a thing that's talked about much.

 

[Marky Dissod]

j91z28d1, your hybrid has an Allison 2ML70 with 3.08, yea?
I've no clue what that geartrain's tow rating is.

Extra ATF cooling is integral to towing, but I'd prefer 3.73 w/ 6L80 & 'base' ATF cooling,
over 3.08 w/ 6L80 & '2500' ATF cooling.

5.3L V8, 6L80E suv.
3.08 is tow-rated 11,000lb. 3.42 is tow-rated 11,500lb. 3.42 w/ K5L is tow rated 14,000lb.
Somehow, I doubt that 3.08 w/ K5L HD Cooling would be tow-rated 13,500lb ...
but if it were, I'd still tune that tcm before the towing.

GM locks & unlocks the TCC for civilian / 1500 suvs & pickup trucks,
very differently from how the TCC locks & unlocks 2500 or heavier-duty stuff.
MpG, Engine Half@$$ mode, and NVH all factor into TCC behavior for 1500 stuff,
which partially (not entirely) explains why GM sacrifices TCC durability for 1500 vehicles,
whereas the TCC lasts far longer in 2500 and up rigs.

 

[j91z28d1]

that's gross vehicle weight right? 11k to 11.5k I could see, but I agree there more to that 14k than just ratio. like I wouldn't put a 4.10 gear in that 5.3 1500 and expect to pull 14k. I'm sure guys have done it thou.


Definitely lots of cooling mods, and I'd guess spring rates, sway bars and stuff.

i don't remember what the tow rating is off the top of my head, I think 6k trailer, 500 tongue. off the top of my head. the 2wd is rated 500lbs higher because of less overall weight. so I was a bit over that trailer wise, but wasn't loaded down with people or luggage and no mountains to worry about brakes. the whole selling point of these things at the time, and also why I think they failed was(beside last of support for the techs) trying to be to everything to everyone. they didn't want to give up tow rating for hybrid stuff like everyone else had and does. 20 years later you're just now seeing hybrids trying to have tow ratings.

but anyways not the point at all. I just personally always wonder if it's the best idea to gear a tow rig so that it needs high gear to do 70mph and of the 2 or 3 guys here that seem to tow very large campers that are well over the ratings all seem to run stock rear gears and use lower tranny gears.

 

[Pyramid_Head]

that's gross vehicle weight right? 11k to 11.5k I could see, but I agree there more to that 14k than just ratio. like I wouldn't put a 4.10 gear in that 5.3 1500 and expect to pull 14k. I'm sure guys have done it thou.


Definitely lots of cooling mods, and I'd guess spring rates, sway bars and stuff.

i don't remember what the tow rating is off the top of my head, I think 6k trailer, 500 tongue. off the top of my head. the 2wd is rated 500lbs higher because of less overall weight. so I was a bit over that trailer wise, but wasn't loaded down with people or luggage and no mountains to worry about brakes. the whole selling point of these things at the time, and also why I think they failed was(beside last of support for the techs) trying to be to everything to everyone. they didn't want to give up tow rating for hybrid stuff like everyone else had and does. 20 years later you're just now seeing hybrids trying to have tow ratings.

but anyways not the point at all. I just personally always wonder if it's the best idea to gear a tow rig so that it needs high gear to do 70mph and of the 2 or 3 guys here that seem to tow very large campers that are well over the ratings all seem to run stock rear gears and use lower tranny gears.

Tongue info in this website made me shy away from towing heavier stuff than what I already haul in my small trailer.

Suburban 2500 (GMT900) towing build - 11th gen -

So we have been rolling with our 2006 Expedition for the past several years. Great truck. Really like it. Super durable and comfortable for the family. Towed like a champ. I would buy another one in a heartbeat if they had a greater tow capacity. Needing a bit more family room and tow capacity...

community.goodsam.com

Anyway, this is besides the point. We decided to just rent a uhaul pickup with a flat trailer and tow it that way. You guys are right. Let uhaul take the wear and tear.

 

[steve45]

Just make sure the rental truck isn't a Ford. A Ford towing a Chevy leaves a bad impression.

 

[petethepug]

A Burb towing a Burb isn’t realistic. You’d be over capacity if you trailer’d it. If you had a tow bar on the Burb being towed that would work but you’d be at the end reach of the Burbs tow capacity. Loading it with stuff that’d increase its GVW would be a no no.

The u haul tow dolly have a total max weight cap of 4k lbs. You’d do best though find someone who already has AAA towing service with the extended range benefit of 1 tow of up to 200 miles per year. That’s their rule here in SoCal, other states may be different.