Visit our Popular Forums

phbarnhart · 03-07-2012, 01:28 AM

Thanks for the comments everyone.

@Sodbust: It's a 6-speed auto, any idea if 4th is still the direct drive?

@mefly2: I was in Montana in October pheasant hunting with a buddy from Helena. I brought the Airstream (obviously) and I noticed that the Suburban seemed a little winded at the elevations around there. MacDonald Pass was interesting.

ROBERT CROSS · 03-07-2012, 06:09 AM

Quote:

Originally Posted by phbarnhart

Thanks for the comments everyone.

@Sodbust: It's a 6-speed auto, any idea if 4th is still the direct drive?

@mefly2: I was in Montana in October pheasant hunting with a buddy from Helena. I brought the Airstream (obviously) and I noticed that the Suburban seemed a little winded at the elevations around there. MacDonald Pass was interesting.

from GM tech...

"Even though the axle is a 3.42 ratio, the transmission provides a wide, 6.04:1 gear ratio that includes two overdrive gears. There isn’t a 1:1 ratio in the specs; the closest is fourth with a 1.15:1. Fifth gear is a 0.85 overdrive and sixth is a 0.66 ratio."

Running in fourth on hills not a concern.
Just put in that gear and run, don't let the PCM try to find it.

Bob

dznf0g · 03-07-2012, 07:53 AM

Quote:

Originally Posted by phbarnhart

Thanks for the comments everyone.

@Sodbust: It's a 6-speed auto, any idea if 4th is still the direct drive?

@mefly2: I was in Montana in October pheasant hunting with a buddy from Helena. I brought the Airstream (obviously) and I noticed that the Suburban seemed a little winded at the elevations around there. MacDonald Pass was interesting.

Yes, 4th is near direct drive. 5th and 6th are both overdrives. Also, as has been mentioned, 1st, 2nd and 3rd are lower gear ratios than the old 4 speeds, so there is greater flexibility and pleasability and capability than with the 4 speeds. Hoewver, you're still pushing it with the high rear end. Just try it and see. It's your truck and your satisfaction that counts.

Edit: I stand corrected:
Transmission General Specifications

Name

6L80

6L90

RPO Codes

MYC

MYD

Production Location

Ypsilanti, Michigan, Toledo, OH (USA), Silao, Mexico

Ypsilanti, Michigan, Toledo, OH (USA), Silao, Mexico

Transmission Drive

Rear Wheel Drive

Rear Wheel Drive

1st Gear Ratio

4.027

4.027

2nd Gear Ratio

2.364

2.364

3rd Gear Ratio

1.532

1.532

4th Gear Ratio

1.152

1.152

5th Gear Ratio

0.852

0.852

6th Gear Ratio

0.667

0.667

Reverse

3.064

3.064

Torque Converter Size– Diameter of Torque Converter Turbine

258/300 mm

300 mm

Pressure Taps

Line Pressure

Line Pressure

Transmission Fluid Type

DEXRON VI®

DEXRON VI®

Transmission Type: 6

Six Forward Gears

Six Forward Gears

Transmission Type: L

Longitude Mount

Longitude Mount

Transmission Type: 80/90

Product Series

Product Series

Position Quadrant

P, R, N, D, M

P, R, N, D, M, I

Case Material

Die Cast Aluminum

Die Cast Aluminum

Transmission Net Weight (Approximate)

100 kg (220 lb)

110 kg (243 lb)

Maximum Trailer Towing Capacity

Refer to applicable owner's manual Refer to applicable owner's manual

Sorry: I hate that charts don't copy well on this forum. Any advice, Moderators?

phbarnhart · 03-07-2012, 11:31 AM

That's great information on the transmission. I have called a couple of independent shops this morning and I'm getting bids to change the gearing.

ROBERT CROSS · 03-07-2012, 11:44 AM

Quote:

Originally Posted by phbarnhart

That's great information on the transmission. I have called a couple of independent shops this morning and I'm getting bids to change the gearing.

Is your 1500 4wd, locking rear diff ?

Bob

**HiHoAgRV** · 03-07-2012, 11:46 AM

Quote:

Originally Posted by phbarnhart

That's great information on the transmission. I have called a couple of independent shops this morning and I'm getting bids to change the gearing.

If you are handy, a low tech fix is a pull-it scrap yard and a proper rearend from a frontal impact. Swap the entire rear end. Our local pull-a-part list the entire rearend for just over $100. I have done some of these swaps...much easier than rear gears

herrick51 · 03-07-2012, 12:01 PM

Quote:

Originally Posted by Lothlorian

You are pulling around 5200 lbs dry weight. That is a call I would not want to make. I would take it to a mom and pop trailer shop, and get their opinion. I have found that businesses who build, repair and sell trailers for hauling are pretty knowledgebale about what you can tow and cannot. I always take my airstream for towing, brakes or axels to those types of shops.

I am pulling 4500 Lbs dry weight airstream with a ram 1500 4.7L engine. It has a 3.55 rear end and a transmission cooler and worry sometimes myself. Especially when I am going up hills. I feel it in the truck. Gross weight I am right at my limit for towing.

Check the side of your door and maintenance book in you glove box and see what the towing capacity is. It should tell you.

Brian

Hello,
I noticed from the spec.sheet that your hitch height is higher than the flying cloud. I'm wondering if your tires are 16 " rather than 15". Some of the dealers feel 16" wheels are to big for the flying cloud. I'll need to check the wheel wells vs the two models but according to GYM chart the sixteens are e-rated vs d for fifthteens.Now fo ryour question. Overloading is a common practice in TV and trailers. Be judicious and take only what you need.Not always necessary to travel with full water tank. Upgrade your transmission maintenace routine to heavy duty and not necessary to drive 70-75 miles per hour. Enjoy.What do you carry in the back of yourTRAILER. DDIE BUE

newroswell · 03-07-2012, 12:22 PM

I totally agree with Red. A ring & pinion set from Randy's for that Suburban (3.42 or even 3.73) is about $265 + a few hours labor (double this if you have 4x4). That should be way less than 4 wheels + 4 LT tires. I don't know, but you may have trouble fitting a smaller wheel over the brake caliper also. Smaller wheels make the pot holes in the road bigger!

phbarnhart · 03-07-2012, 01:05 PM

@Bob: I'm pretty sure that it is a locking rear diff (automatically) and yes, its a 4wd.

@Herrick: Yes, the Eddie Bauer has 16" wheels so it's a little taller than normal but that actually works pretty well with where the hitch receiver is on the Suburban. Once I fill the fresh tank it's (by the specs, mind you) around 6000lbs. Then we add clothes, food, the small generator (if going boon docking), and a few toys for the kids. I don't know the weight of all of the dishes and the like, but I was pretty careful about picking out light items. I would be pretty surprised if we end up over 6500lbs but I'm planning on finding out soon.

ROBERT CROSS · 03-07-2012, 01:18 PM

@Bob: I'm pretty sure that it is a locking rear diff (automatically) and yes, its a 4wd.

G80 is the option code for the locker.

Bob

phbarnhart · 03-07-2012, 01:37 PM

Excellent, thanks Bob.

phbarnhart · 03-07-2012, 01:45 PM

Update: Apparently the 3.08 rear-end is in an 8.5" housing and the 3.42 gears will not fit in that. GM doesn't sell a complete 3.42 housing (just the individual parts) but they do sell the 3.73 housing complete. So the guy has some of his contacts at the wrecking yards looking around for a complete 3.42 set-up.

ROBERT CROSS · 03-07-2012, 02:59 PM

IMHO.... if your serious about changing, go for the 3.73, you would be hard pressed to notice the difference going to the 3.42. And remember the front differential needs the up-grade too.

Bob

Jammer · 03-07-2012, 03:05 PM

I have the 3.73 rear in my pickup and the 4.10 rear in my 'burb. They have the same transmission but the 'burb has a bigger engine.

The only difference is that the 3.73 leads to more hunting between 3rd and 4th on hills with the trailer (I have the 4 speed transmission, not the newer six speed). I don't notice a difference in noise level or fuel economy.

Things may be a little different with the 6 speed transmission, but in general, if you're doing a significant amount of towing, you'll want a lower (numerically higher) ratio rear. 3.73 would be fine if that's what's available, I would think, 4.10 probably ok too, 4.31 might be too much of a good thing but maybe not.

phbarnhart · 03-07-2012, 04:42 PM

My understanding is that the 6-speed has made some of the traditional wisdom about which rear-end ratio to go with a little less applicable because the availability of more gears means that you're more likely to have the right one available.

That said, I may very well end up with the 3.73, especially if the mechanic can't find a suitable set of 3.42s!

dznf0g · 03-07-2012, 04:53 PM

Quote:

Originally Posted by phbarnhart

My understanding is that the 6-speed has made some of the traditional wisdom about which rear-end ratio to go with a little less applicable because the availability of more gears means that you're more likely to have the right one available.

That said, I may very well end up with the 3.73, especially if the mechanic can't find a suitable set of 3.42s!

Well, IMO, it made the issue of 3.73 vs. 3.42 less of an issue in your weight class.

ROBERT CROSS · 03-07-2012, 05:06 PM

Quote:

Originally Posted by phbarnhart

....a suitable set of 3.42s!

One more time....two suitable set's.

IMHO..a lot to spend for .34 of one revolution.
Any math geeks out there?

Bob

newroswell · 03-07-2012, 05:24 PM

Quote:

Originally Posted by ROBERT CROSS

One more time....two suitable set's.

IMHO..a lot to spend for .34 of one revolution.
Any math geeks out there?

Bob

Think of it as 9% more torque in every gear. But yeah, with the 6 speed, it means that on any given hill, you may be in 4th instead of 3rd at the same speed & RPM...

I'm with the not sure you have a problem and this isn't a minor expense group.

phbarnhart · 03-07-2012, 05:35 PM

@ Bob: Yeah, I know I need to change the front and back, I thought that my use of "set" followed by a plural "3.42s" showed that. I guess that since each end actually needs a set of gears it wasn't clear. Anywho, I'm hoping that they can find a front/back gearing set from a single vehicle.

@ newroswell: I noticed on my trip to Montana and back last fall that I didn't quite have enough power to cruise on the freeway in 5th but that 4th was more than was necessary. I'm thinking that 9% would be just about right. What I do know is that I had to drop to 2nd on a few of the mountain passes because 3rd was, again, just by a little bit, unable keep up momentum.

My real concern was about the durability of the 3.08 gears/housing as compared to the 3.42 or 3.73. It seems that the housing is smaller on the 3.08 but I don't know if that matters all that much. Anyway, I'm exploring my options right now.

dznf0g · 03-07-2012, 05:45 PM

I still say try it the way it is and see if it is comfortable for YOU, performance wise. There's plenty of time later to swap out gears (yes, 2 sets!)

If you were trying to pull a 30'er or a 34'er, I'd be much more concerned about durability, etc. Not so much with a 25'er.