Gear swap time: Turns out I have 3.42 gears

[justme1969]

I agree with all except your eaton posi. AN auburn gear pro. will grip as good unless you dont set it up for your applicaion. But key here is it will unlock under high load for road driving.
I was told full spool and ox locker blah blah blah from fellow hill billies then 4w and off road parts house took me out in a Auburn pro equipped jeep It was full on all 4 wheels till we pulled back into parking lot where a l/h turn resulted in a chirp and subsequent unlock.
My 90 4wd sub has front and rear with lock outs in front.
When in 4wd it is very much like a 4wd spooled tractor.
If it ever meets the road again I will turn them down more because they wouldnt always unlock on wet pavement. but thats the thing I can open the diff and adjust spring tension. Not stuck dragging a tire around every turn.

[oil pan 4]

I like the alburn too.
Only problem is I have the eaton in my possession right now.

Its a 2wd suburban I just don't want to get stuck on wet grass or soft sandy soil. Driving on gravel roads and through fields is about the extent of what my off road should be.

[slowmover]

Originally Posted by oil pan 4

An NV4500 would be pretty cool but they are kind of hard to find and expensive.
Plus I don't really want to do a flex plate to fly wheel swap, my rotating assembly is machine shop balanced.

I know of the gearvender over drive units but at $2k its way out of my price range.

Can you find the towing spec for your year Sub/drivetrain? Along with front and rear axle ratings I think we can set a reasonable number for you to work with (trailer weight). Any truck ought to be set up to a standard, IMO, one that one can live with as the work capacity of a truck is easily as important as its operational costs. The balance of the two is the definition of what a truck is, again IMO. Altitude de-rate is part of that for a truck meant to be economical.

.

[oil pan 4]

My suburban has a 5,000lb tow rating.
The gas powered version has a 6,000lb tow rating.

My version of suburban has load range C tire, 3/4ton rear springs, an insanely over built trans monitoring, cooling and filter system, a trailer braking system (not in use with my little trailer) additional engine oil cooler and a couple of turbochargers with an intercooler.
The most I ever plan on doing with it is towing a car dolly with a car on it, which could weigh in up to 4000lb depending on the car.
That should happen at least a few times a year and it will be a long drive when it does happen, 4hr minimum. Plus numerous little car pull jobs in between.

[Big Dave]

Coupla things:

Somewhere in the archives of The Diesel Page - for the 6.2L, 6.5L, and Duramax 6600 (6.6L) GM Chevrolet and GMC diesel engines. there is a story out of GM about a 6.2 normally aspirated diesel with a 700R4 and 2.73 gears that got 30 MPG without hypermiling. IMO this thing would be so slow any driving it would be virtual hypermiling. Look for the story.

Back in the 80s and 90s I had a 6.2 diesel with a 700R4 in a K2500 pickup. Not much heavy work unless you count hauling my fat butt around. Good truck - got about 23 MPG but went through transmissions like a teenager goes through potato chips. By time I got rid of it at 305,000 miles it had trashed its seventh transmission. spectacular failures with parts and tranny fluid scattered down the road.

My advice to a good mechanic: Transplant in a manual. NV4500s fit well. T5s are too light.

Also a manualwould enhance MPG.

[oil pan 4]

Originally Posted by Big Dave

Coupla things:

Somewhere in the archives of The Diesel Page - for the 6.2L, 6.5L, and Duramax 6600 (6.6L) GM Chevrolet and GMC diesel engines. there is a story out of GM about a 6.2 normally aspirated diesel with a 700R4 and 2.73 gears that got 30 MPG without hypermiling. IMO this thing would be so slow any driving it would be virtual hypermiling. Look for the story.

Back in the 80s and 90s I had a 6.2 diesel with a 700R4 in a K2500 pickup. Not much heavy work unless you count hauling my fat butt around. Good truck - got about 23 MPG but went through transmissions like a teenager goes through potato chips. By time I got rid of it at 305,000 miles it had trashed its seventh transmission. spectacular failures with parts and tranny fluid scattered down the road.

My advice to a good mechanic: Transplant in a manual. NV4500s fit well. T5s are too light.

Also a manualwould enhance MPG.

Oh these are well known to a lot of people in the 6.2L/6.5t world.
Its usually a C5 blazer, with a 6.2L, an after market gale banks turbo, 5-speed with 3.08 rear gears.
I could see a N/A 6.2L doing it with 2.73 gears as long as you didn't have any where you needed to be in a hurry.

I would like to do a manual swap some day I just cant do it now.

[oil pan 4]

I can get used 3.08 gears for $30 to $50 on ebay and a seal kit for $35.
My eaton posi has axle bearings and I can get a pinion bearing set for less than $66 if needed.
How can I afford not to?

[UFO]

Sounds perfect.

[oil pan 4]

I think I just might push it a little bit and install 2.73 gears.
Playing with the gear and tire size calculator going from 3.42 gears to 3.08 may not be a big enough change to give much results.

[aardvarcus]

Oil pan, your new gearing will be about 20% lower, I would suggest you take your burb for a ride at a 20% lower speed than your normal cruising speed. For example if you cruise at 60, then make a short trip at 48, and make sure you are in overdrive. Pull an empty trailer or put some stuff in your suburban to increase the weight by 20% if you can. This will be a good inexpensive simulation of what it will be like with the gear change. Make sure your new rpm’s aren’t going to put you in a bad spot where you are constantly lugging the engine on inclines.

I know you don’t want to do a manual swap right now, but for those reading this that are considering it, one thing to remember is that if your low or first gear is low enough and your gear spread is appropriate you can support a taller rear end gear with minimal loss in performance. For example, in first gear having a 5:1 first gear and a 2.73 rear end gear is basically the same as having a 4:1 first gear and a 3.42 rear end. Also the gearing effects of stock/oversize/undersize tires must also be taken into effect. It is important that we keep the entire drivetrain system in context, and not propagate generalizations.

Oh, and if you keep your eyes open you would be surprised at what you can find, NV4500s aren’t that rare. Don’t bother calling about the “NV4500 best transmission ever bring $$$$” adds, look for the “Parting out 1995 3500 Truck” adds and call and ask if it has a manual transmission with the cast iron case.