3.08 Rear End

[bruceb58]

Re: 3.08 Rear End

There are only 2 rear end options on the Tahoe, 3.08 and 3.42. With the 3.08, the rating is 5100lbs.

 

[oldjeep]

Re: 3.08 Rear End

There are only 2 rear end options on the Tahoe, 3.08 and 3.42. With the 3.08, the rating is 5100lbs.

It also appears that with the towing package that they do install an extra tranny cooler.


STRIKE ONE - does your truck have a tow/haul switch? Most fullsized pickups have them now, they will disable overdrive and change the shift behavior of the tranny.

 

[STRIKE ONE]

Re: 3.08 Rear End

Thanks for all the opinions and advice. To answer a few questions, it is a new Tahoe w/ the 5.3 motor, 6 speed trans (I like that) and tow/haul mode. I've not towed the boat with it as we are still breaking in the motor, but plan on just getting out and using it without too much worry since I'm not towing as tug boat as one fellow mentioned. Kinda anal....need everything to be pretty much right but I hope to get over this snafu and enjoy the truck and the boat. At least the wife is happy because as the old saying goes, if momma ain't happy....then nobody's happy! I'll post feedback later after I tow with it.

 

[Floatsum]

Re: 3.08 Rear End

Not going to hurt anything to at least try it.

But, I'll stand by my original statement. Not so much because it would be sluggish (though it may be), it's because of strain.
3.04 ratio allows much more strain on things like tranny, mounts, U-joints, bearings, etc. also makes the engine work harder and may encourage issues latter down the road. Nothing exciting right away though.

My comment may not matter if you're only hauling once or twice a year. But if it lives on the trailer and tends to make frequent trips I still think it'll shorten the life of a new anything over a relatively small amount of time (as compared to not).

My reasoning is from towing a lot of trailers of different types over many years. (but things change too)

 

[STRIKE ONE]

Re: 3.08 Rear End

Not going to hurt anything to at least try it.

But, I'll stand by my original statement. Not so much because it would be sluggish (though it may be), it's because of strain.
3.04 ratio allows much more strain on things like tranny, mounts, U-joints, bearings, etc. also makes the engine work harder and may encourage issues latter down the road. Nothing exciting right away though.

My comment may not matter if you're only hauling once or twice a year. But if it lives on the trailer and tends to make frequent trips I still think it'll shorten the life of a new anything over a relatively small amount of time (as compared to not).

My reasoning is from towing a lot of trailers of different types over many years. (but things change too)

Agreed. That's what my concern was and why I've been kicking my own butt....shortened life span for the drive train due to limitations of the 3.08 rear end and lack of heavy duty towing package. I've made worse mistakes but I have a lot of money invested in this one!

 

[dockwrecker]

Re: 3.08 Rear End

Nah just add the cooler. The six speed will be fine, it might be happiest in 5th towing, just experiment a little. I have the 6 speed in a k2500 pulling 6200 lbs. and using the tow/haul button, I just let it do it's thing. It's an Allison trans, durable as hell and I wouldn't worry about it so much. The first 3 gears are so low you'll have no trouble getting up a ramp.

 

[smokeonthewater]

Re: 3.08 Rear End

all this fuss is over nothing..... 3.08 to 3.42 is a SMALL difference...... I gross at over 26,000 lbs in my truck often and have a 4.10 rear.... 3.08 with the truck you have and the little load you will haul will work GREAT.... You will hardly notice that boat behind you and if you floor it from a light you'll likely leave rubber on the road even while towing it.

If you don't already have one go have GM add the aux trans cooler (it will be mounted better and plumbed in better than joe at the quick lube will do it), hit the tow/haul button and set the cruise on whatever speed you want to run..... Also refer to your owners manual on gear selection for towing.... While you're at it read the whole thing... you may pick up one or two other usefull tidbits

Now if you go lifting the truck and putting big tires on it you will likely need to regear but bone stock it is rated and WARRANTEED to tow more than your boat in mountains at highway speed for the entire warranty period ..... far more abuse than you will put on it going fishing or skiing even twice a week


As was stated above a time or two You'll be FINE...

 

[Bifflefan]

Re: 3.08 Rear End

An issue that everone seems to be missing,
I doubt that the boat, trailer and gear is over 3200 lbs. My 22 with a two axle trailer, gas and gear weighs 4200 lbs. And its a 1984, when they really built stuff.
I see no issues with the 3.08, and remember you dont tow all the time.

 

[c5streak]

Re: 3.08 Rear End

Hey guys! I've been lurking for a while, just soaking up all the good info. I finally see a topic that I may be able to give back on. A 3.08 diff is not a big problem with the 6 spd tranny. The ratios of the 6 gears are spread out so that your Tahoe will shift when it needs to without the jarring "passing gear" effect of the older 4 spd ATs. In recent years, I've had the 5.3 in almost every combo of trans/rear ratio. The 6 spd can handle the higher axle ratios way better than the 4 spd ever could, as far as keeping your engine in a comfortable power/RPM range and still be fairly efficient. If your concerned with all of the shifting the 6 spd does (which is normal), then shift into "M" and select 4th or 5th, whichever is suitable to speed, terrain, load and wind conditions. The trans will downshift very little then and keep your MPH steady with alot less downshifting. My previous truck was a 5.3/4spd AT/ 4.10 rear. My current 6spd/3.73 truck is a whole other animal when it comes to pulling my '94 Astro 18' F&S. Granted it's not a heavy load, but the 6 spd is so much smoother when shifting back and forth at highway speeds under load. A tranny cooler is always a good option, but by selecting a lower manual gear, you save a lot of shifting by the tranny. Shifting builds heat. Heat kills trannys. As a last resort, find a reputable shop and have them install 3.73's, they work wonderful with the 6L80E trans. I had the 4.10s installed for about $600 per axle(4X4). The difference from the 3.42s was impressive. However the 6spd/3.73 is still WAY better!
In the end, if GM says it'll pull 5400 as is, then I wouldn't worry.
Just my .02.
Good luck and enjoy your new ride and your boat!

 

[TilliamWe]

Re: 3.08 Rear End

I have the 6 speed in a k2500 pulling 6200 lbs. and using the tow/haul button, I just let it do it's thing. It's an Allison trans, durable as hell and I wouldn't worry about it so much...

dock, I just want to make sure you know, the 6 speed in the 1500s with the gas engines is NOT an Allison, it's a 6L80E GM transmission.

 

[Titanium48]

Re: 3.08 Rear End

I suppose this is another of those threads that could go on forever but my point about such high gearing is that while deep first and even second gears is essential to get you moving, once moving, that axle ratio is just as important to maintain high engine vacuum which translates directly to economy.

Not true. Pulling air past a nearly closed throttle is a waste of energy. Sometimes this is good (like when you gear down on a steep downhill grade), but usually the higher the vacuum, the less efficiently your engine is operating. This is why cylinder deactivation works - turn a V8 operating at high vacuum into a 4-cylinder operating at low vacuum and you get the same power output with less fuel input. Alternatively, operating at lower vacuum and lower RPM will use less fuel for the same power output than operating at higher vacuum and higher RPM. The only exception is when the engine computer retards timing or adds more fuel at WOT to prevent knocking.

Using your 3.21 vs a 3.08 gear as an example. That represents a fairly significant difference in power delivery to the rear wheels. Newer vehicles also tend to run much larger tires than trucks did in the past so that is another factor that alters effective axle ratio. HP, axle ratio, terrain and truck useage all must play together in order to optimize the balance between performance and fuel economy. This boils down to how much towing one does and the terrain where one must use the vehicle the most. If you live in Kansas or Nebraska for example, 3.08 gears in truck that doesn't tow anything might work fine and get great fuel economy. Hook up a horse trailer or similar and you would beg for deeper gears.

But you have those deeper gears with the 6-speed transmission. A high top gear to keep the engine speed (and vacuum) down when you don't need much power, lower gears to let the engine rev up when you need more power, and close enough spacing to prevent "flat spots". Heavy trucks have had a dozen or more gears for decades - pickups and SUVs are finally starting to catch up.

Even strong headwinds affect performance and it is magnified by high gearing. One of the most annoying trips I ever made was driving my brothers Toyota Highlander to Colorado. On even the slightest grades the tranny would not stay put and even my wife commented if something was wrong with this vehicle. I had to drive less than the 75 MPH posted speed in Nebraska because this vehicle would not stay in top gear and it reved like nuts out of OD. Needless to say this vehicle is not an economy champ either. Big difference in vehicles to be sure but the concepts still apply. No vehicle I've ever owned behaved so poorly.

Sounds like the spacing between OD and the next gear down was too big. More gears = closer spacing = less annoying when the tranny does it's thing and shifts in response to changing power demands.

 

[dockwrecker]

Re: 3.08 Rear End

dock, I just want to make sure you know, the 6 speed in the 1500s with the gas engines is NOT an Allison, it's a 6L80E GM transmission.

Didn't know that! Thanks for the heads up.

 

[BigB9000]

Re: 3.08 Rear End

I has 3.73's put in my caprice.
I noticed no difference, and feel I have wasted my money.

The other problem is the speedometer is now way off. it says I'm doing 86 at 65. Putting more miles on the thing than there actually is, its a $200 reprogram I'm not looking forward to.


+1 on the trans cooler though. I have blown through 2 transmissions, the 3rd will have a cooler, a deep pan with those little cooling fins, a temp gauge, and whatever else I can do to make sure I don't eat up trannys anymore.

Never tow in OD

 

[osudelt69]

Re: 3.08 Rear End

My dad has a 2005 Silverado 1500 with 5.3 and 3.23 rear end. He tows a much bigger boat than yours and also a two horse trailer. Silverado tows as good as his old 1500 Ram with Hemi and 3.92 rear end. NO ISSUES what so ever. In fact it tows so well he said he will NEVER get a bigger rear end again. Ensure you have a transmission cooler, hitch, and proper wiring harness. Your Tahoe won't even know the boats back there and you'll get better gas mileage when not towing than 3.42 rear end. Make sure you use the tow/haul mode and your PERFECT!! Don't even sweat it!

 

[25thmustang]

Re: 3.08 Rear End

An 18' boat, more or less any 18' boat, behind a full size truck... Far too much worrying about gear ratios.

We towed a 5000 lb car trailer for years with a 91 S10, with the TB 4.3. It sure didn't like the hills, but we're talking more weight, with FAR less power.

Hook it up, and enjoy the ride.

 

[jkust]

Re: 3.08 Rear End

As the lowest common denomonator, for one season, prior to buying a true tow vehicle, I pulled my 4000 lb boat/trailer with a fwd, 185hp/210tq minivan with way over 100,000 miles with a 3.29:1 ratio. As unvelievable as it sounds it did a semi respectable job considering how inadequated it is on paper. Your tow rig is light years ahead and will surely be just fine. When purchasing my SUV, 90% of the focus was on the getting the upgraded tow equipment. I must admit it was actually hard to find all the stuff from the 5.3/G80 locker/3.73's etc all on one vehicle. Dealers were a little annoyed that I cared about those things since almost none of the midsized SUV's actually had those unseen options.