Thoughts on going to a 4spd overdrive?

[Grit dog]

I’d second the 4L80 swap if you need OD.
Other things to consider, first figure out what gears you have and add a tach to see if it really is screaming.
These are “higher” max rpm engines than you might expect.
Redline is 3600 with a load and I believe 4000 max.
Of course you don’t want to put up with 3500 rpms all day, but if its 4.10 gears, you may be close to that with those tires at 70mph. For comparison, my 4.10 turbo400 truck is at 3000rpms at 70mph (gps, still need new speedo gear to correct speedo) with “35s” that are sitting at an actual 33.5” diameter.
If you’re towing 5klbs even at sea level and flat, I would NOT gear the axle up at all. 6.2 is pretty anemic and would struggle with tall gears towing IMO.
First see what rpms you’re actually running at your desired cruising speeds. If it’s not that bad, maybe a muffler is all it needs for your driving pleasure!

That burb is really nice btw!

 

[Grit dog]

Suggestion, I’d “pre-sell” your TH400 before the swap. you’ll get more $ for it if someone can put their foot to the floor and test it rather than trusting you that it’s a good trans.

 

[Burban1990]

My 88 suburban came with a 700R4 that has a shift kit. To be honest I wish it still had the turbo 400 in it especially with a 6-in lift and 35-in tires. Even though the transmission doesn't have a whole lot of miles on it I know I'll be able to at least use it for a couple of years if not longer. 4L80E in my opinion is the better option.

 

[shiftpro]

The other option is a Gear Vendors overdrive. Cost is probably more than the 4L80. Sometimes you can find these on old motorhomes with the P30 chassis.

Absolutely, late 70's early 80 motorhomes, which are basically free.

 

[Grit dog]

Absolutely, late 70's early 80 motorhomes, which are basically free.

As long as you can rob the GV and split. Otherwise getting rid of a Moho will cost you almost as much as a new off the shelf GV, unless you have an excavator, a buddy in the dumpster service and a hot saw or torch!

 

[Grit dog]

My 88 suburban came with a 700R4 that has a shift kit. To be honest I wish it still had the turbo 400 in it especially with a 6-in lift and 35-in tires. Even though the transmission doesn't have a whole lot of miles on it I know I'll be able to at least use it for a couple of years if not longer. 4L80E in my opinion is the better option.

If our 86 was going to be pounding out the freeway miles, the 4.10s even with 35s isn’t practical. But for a Sunday driver/toy the TH400 is da bomb!

if your burb has 3.73s the 3 speed would be a little more palatable on the highway.

 

[shiftpro]

As long as you can rob the GV and split. Otherwise getting rid of a Moho will cost you almost as much as a new off the shelf GV, unless you have an excavator, a buddy in the dumpster service and a hot saw or torch!

Fill it up with democrats, weld the doors shut and dispose.

 

[Rusty Nail]

700r4 is junk x2

I remove those to install what you have now but only because they are one million times a better transmission. I will NOT advocate removing turbo 400 to replace with 700r4, ever.

Nor do I support retrofitting modern vehicle electronics into a classic anything. See all that techno mumbo jumbo them dudes are talking about up there? Aint got no place in your 83..thats my opinion. K.I.S.S. you'll make it unreliable.
Forever.

Many dudes that get in these trucks and worry about gas mileage really floor me. - If you cant afford to drive one why did you buy it? Thats what it boils down to. Gas Money .
Youd be better off with something else newer thats fuel injected so you wouldnt or couldnt find need to fock with it and fock it up. Go tear up some new plastic garbage instead of an old square huh? Make your life EASIER instead huh? I bet it'll get real good gas mileage and may even be shiny! Oh! You could get new black wheels and blue headlightsss. VORTEX HEDS!
Ohhh! Ahhh!

I think you made a bad purchase and you should sell it. That's my opinion.
About that.

 

[Camar068]

Plenty can be done to a 700r4/4l60. Keep googling, look for reviews, gain knowledge, and form your own opinion with wallet in mind. 2 links below

Extreme 700r4/4l60e

700r4

 

[Matt69olds]

The 700 is far from junk. Built and installed correctly, and not behind a really stout engine, they live just fine. The problem is most people don’t want to pay for the upgrades to make them live.

 

[SquareRoot]

700r4 is junk x2

I remove those to install what you have now but only because they are one million times a better transmission. I will NOT advocate removing turbo 400 to replace with 700r4, ever.

Nor do I support retrofitting modern vehicle electronics into a classic anything. See all that techno mumbo jumbo them dudes are talking about up there? Aint got no place in your 83..thats my opinion. K.I.S.S. you'll make it unreliable.
Forever.

Many dudes that get in these trucks and worry about gas mileage really floor me. - If you cant afford to drive one why did you buy it? Thats what it boils down to. Gas Money .
Youd be better off with something else newer thats fuel injected so you wouldnt or couldnt find need to fock with it and fock it up. Go tear up some new plastic garbage instead of an old square huh? Make your life EASIER instead huh? I bet it'll get real good gas mileage and may even be shiny! Oh! You could get new black wheels and blue headlightsss. VORTEX HEDS!
Ohhh! Ahhh!

I think you made a bad purchase and you should sell it. That's my opinion.
About that.

Agree. 700r4 is junk x3
You misspelled VORTEX @Rusty Nail. But you probably did that on purpose?

 

[Grit dog]

700r4 is junk x2

I remove those to install what you have now but only because they are one million times a better transmission. I will NOT advocate removing turbo 400 to replace with 700r4, ever.

Nor do I support retrofitting modern vehicle electronics into a classic anything. See all that techno mumbo jumbo them dudes are talking about up there? Aint got no place in your 83..thats my opinion. K.I.S.S. you'll make it unreliable.
Forever.

Many dudes that get in these trucks and worry about gas mileage really floor me. - If you cant afford to drive one why did you buy it? Thats what it boils down to. Gas Money .
Youd be better off with something else newer thats fuel injected so you wouldnt or couldnt find need to fock with it and fock it up. Go tear up some new plastic garbage instead of an old square huh? Make your life EASIER instead huh? I bet it'll get real good gas mileage and may even be shiny! Oh! You could get new black wheels and blue headlightsss. VORTEX HEDS!
Ohhh! Ahhh!

I think you made a bad purchase and you should sell it. That's my opinion.
About that.

You do realize you revived a year old thread that the OP hasn’t even posted here in almost that long, right?
And that the OPs truck is a diesel (whatever you were rambling about fuel injection and vortex? heads).
And you ended it by basically saying the OPs Burb is a piece of ____? (I’m sure he won’t care since he ain’t been online here in almost a year, but it sounds funny coming from you who seems to have constant issues with your squares and by your posts it appears that yours either aren’t roadworthy or have frequent problems). When he actually appears to have purchased a very clean good running truck?

Your post sort of sounds like Aurora girls alter ego or something.

 

[Vbb199]

You do realize you revived a year old thread that the OP hasn’t even posted here in almost that long, right?
And that the OPs truck is a diesel (whatever you were rambling about fuel injection and vortex? heads).
And you ended it by basically saying the OPs Burb is a piece of ____? (I’m sure he won’t care since he ain’t been online here in almost a year, but it sounds funny coming from you who seems to have constant issues with your squares and by your posts it appears that yours either aren’t roadworthy or have frequent problems). When he actually appears to have purchased a very clean good running truck?

Your post sort of sounds like Aurora girls alter ego or something.

My favorite part of this is the 1 sided opinions based on very limited experiences in life

"one time some .... uh ... i think 700r4 blew up ... and uh... one day i put in what i uh... think was a th400,... and uh, my underpowered motor didnt blow it up... so uh.... 700r4 bad, and if you dont follow my path, you're gonna have all sorts of problems, because my 1 opinion defines all automotive standards"

 

[DoubleDingo]

......I believe it's a 4.10 rear, the fender tag just says "standard" for rear axle, would going to a 3.55/3.73 make a big difference? any idea what rpm I'm running at at different speeds? ....

Yes! 3.55 would get your about 2,600 at 70. It's a great gear. The 68-72 C20 suburbans had those gears. I found one of those axles and went from 4.57 to 3.54 and it was night and day difference in a great way. With the TH400 it would be a nice highway cruiser. Those C20 suburbans had 396/TH400/3.54 Dana 60. I don't know if you can get a 3.55 gear for your axle, but it would be the easiest swap option if it's doable.

EDIT: LOL...I saw October on page 1 but didn't pay attention to the year...lol...yeah an old thread and nothing back from the OP

 

[Blue Ox]

Whoa. And they say I belittle people...