"Hypothetical" Question (Wink Wink)

[dsteelejr]

Say I were to somehow come into ownership of an '86 Suburban C20 with a 454, th400, and 4:10 gears.

"Hypothetically" would a "hypothetical" Th700r4 survive behind a "hypothetically" stock "hypothetical" 454? The "hypothetical" Th400 is still good, but with the "hypothetical" 4:10 gears, the gas mileage is "hypothetical" ****. So I'd like to "hypothetically" swap the "hypothetical" Th400 for a "hypothetical" Th700r4.

Is this a good "hypothetical" idea? A "hypothetical" Gear Vendors Overdrive is out of the "hypothetical" range of my "hypothetical" wallet. Also I don't want to deal with a "hypothetically" complicated and "hypothetically" expensive "hypothetical" 4L80E swap.

Or should I just "hypothetically" swap the "hypothetical" 4:10 gears in the "hypothetical" 14 bolt rear end for some "hypothetical" highway gears.

"Hypothetically," I'd want to put a lot of highway miles on this truck, so the "hypothetical" current set up wouldn't "hypothetically" work.

What do you guys think about this "hypothetical" scenario?

I’m a lot less knowledgeable than some of the other commenters on here, but I know enough that I would never swap out anything for a 700R4. I had an ‘84 K5 years ago and was not happy with the 700R4. On the other hand I currently have a ‘73 C20 with a 350 engine and TH350 and it does great. The TH350 has been rebuilt twice in its life because of ordinary wear and tear, never any issues. IMHO stay away from the 700R4.

You’d be better off changing your rear end gears, but I don’t think the juice is worth squeeze. It’s a 454. If you’re concerned about fuel economy you’re looking in the wrong place.

 

[Ricko1966]

I'll send a picture and tag you in it next time i do 100 with a screenshot of google map's "speedometer function"

Mine would do it all day long.

 

[rt66paul]

TH400 is a pretty strong trans, it has its limitations, but when they break, they are cheap and easy to fix. Replacing this with the 4L80E might be ok, but it is expensive. I really wonder if you can really justify the cost with increased fuel mileage,, but it is your money.

 

[DoubleDingo]

I think all this "hypothetical" S#$@ needs to go away?.........but I will say @jjester6000 got a pretty decent ride,....NOT hypothetically

I read about two hypotheticals and stopped reading. Lame. The other responses are good somewhat. And it is a nice score.

 

[AuroraGirl]

Say I were to somehow come into ownership of an '86 Suburban C20 with a 454, th400, and 4:10 gears.

"Hypothetically" would a "hypothetical" Th700r4 survive behind a "hypothetically" stock "hypothetical" 454? The "hypothetical" Th400 is still good, but with the "hypothetical" 4:10 gears, the gas mileage is "hypothetical" ****. So I'd like to "hypothetically" swap the "hypothetical" Th400 for a "hypothetical" Th700r4.

Is this a good "hypothetical" idea? A "hypothetical" Gear Vendors Overdrive is out of the "hypothetical" range of my "hypothetical" wallet. Also I don't want to deal with a "hypothetically" complicated and "hypothetically" expensive "hypothetical" 4L80E swap.

Or should I just "hypothetically" swap the "hypothetical" 4:10 gears in the "hypothetical" 14 bolt rear end for some "hypothetical" highway gears.

"Hypothetically," I'd want to put a lot of highway miles on this truck, so the "hypothetical" current set up wouldn't "hypothetically" work.

What do you guys think about this "hypothetical" scenario?

Hypothetically you could just donate either the th400 or the 700r4 to me and I can help decide which would suit you more and work by testing, hypothetically, so you can know definitely which would be good in half the time!

 

[AuroraGirl]

I read about two hypotheticals and stopped reading. Lame. The other responses are good somewhat. And it is a nice score.

Tl;dr,
86 bourbon with th400, would 700r4 last behind it in order to get more MPG
Presumably he either has a 700r4 or can get one decent and presumably the engine is running stock or smogless enhanced and maintained, so slightly more than a factory late 80s big block

he’s got the square now for heavy lifting I think he would like to utilize a bourbon for DUI I mean daily driving

 

[AuroraGirl]

Some people and their internet buddies have just had a few 82-86 200,000+ mile 700r4's quit on them, and now they have a bad rep.

Theyre not garbage, but like matt said, if you're pushing the kinda power that 90% of the 700r4 haters dont even have, then i'd upgrade.


Im not preaching the 700 sermon for my big block c10, and i wont, because i know it'll never survive.
Shes making 600hp figures

But in a <400 hp app, run the **** out of a 700

Tv cable and a trans cooler being the best aids to a long fruitful life

 

[AuroraGirl]

Hypothetical is ********. Real world that 700 won't survive for long unless you drive like your 80 years old. 4l80 or nv4500. You want a daily driver? LS swap or PF-4. Don't even ask about gas mileage. If you have to ask, you can't afford it. Carry on.

Woah who’s kitty litter did you get caught shitting in calm yourself

 

[AuroraGirl]

If he didn’t have an already large tire a slightly larger tire could help bump that too and some HT Tires

3.42 gears would probably work pretty well for what you are looking to do.

It is a BBC, so you have to be realistic about fuel economy. Swapping the gears is probably the most economical plan and it will get your cruising RPM’s down some and should improve the mileage some.

 

[Circular Pastry]

Hypothetically I can sell you the 65k mile one I'm switching over to amsoil, but not until after we get back from vacation. …I'm hypothetically going 8 speed w/standalone mgmt, because gas mileage un-hypothetically still sucks in a 12 passenger G30.
…I had looked at gearvendors first. (just don't want another fluid to have to change every oil change)

Sent from my moto x4 using Tapatalk

 

[Bextreme04]

Just leave it be. You are never going to save enough money on gas with any of those changes to make up for the cost of the change. You'll need a different driveshaft(or at least a different yoke) going to a 700R4 also. The most economical thing would be to find a cheap rear end with low gears(maybe from a 6.2 truck) or just buy a gearset that matches what you want. 14 bolt carrier break is at 4.10 and lower so you should be good with just a gearset.

 

[Gearheadsqce]

Something you might consider:

Quickchange Rear Axle
I have been building these for 35+ years. They are based on 1938-62 Ford 3/4 ton internals. Still used in circle track racing, so replacement parts are plentiful and reasonable. 5 on 5 Bolt circle is common but others can be had. Full floating axles, too.

I even built a dually for a customer.

Final drive ratios form the low 2s to 8s.

I have one in my 454 Crew Cab. Turbo 400.
Can change gears in under 10 minutes. Not something you want to do every day, but when planning a long trip or tow you can dial it in.

Not cheap, and not for everybody but it is a viable alternative.

Message me for details or a quote.

 

[AuroraGirl]

Hypothetically I can sell you the 65k mile one I'm switching over to amsoil, but not until after we get back from vacation. …I'm hypothetically going 8 speed w/standalone mgmt, because gas mileage un-hypothetically still sucks in a 12 passenger G30.
…I had looked at gearvendors first. (just don't want another fluid to have to change every oil change)

Sent from my moto x4 using Tapatalk

You seem new and are obviously new I demand to see this g30 and welcome


If it isn’t pimped out or hippied I will be sad

but I still want to see

 

[AuroraGirl]

Something you might consider:

Quickchange Rear Axle
I have been building these for 35+ years. They are based on 1938-62 Ford 3/4 ton internals. Still used in circle track racing, so replacement parts are plentiful and reasonable. 5 on 5 Bolt circle is common but others can be had. Full floating axles, too.

I even built a dually for a customer.

Final drive ratios form the low 2s to 8s.

I have one in my 454 Crew Cab. Turbo 400.
Can change gears in under 10 minutes. Not something you want to do every day, but when planning a long trip or tow you can dial it in.

Not cheap, and not for everybody but it is a viable alternative.

Message me for details or a quote.

Darn... too bad the 2 speed rear axle from late 40s and early 50s 2 ton dually isnt that..

But I think I might have one of those fords.... I only have the guts or carcasses of 5 pre 1970 vehicles, 6 if you count a tractor that originally was a model t or a and was converted during the depression

 

[AuroraGirl]

My '78 Burb pulls real well up to 100mph and beyond. GPS certified too (stock speedo is about useless these days).

Is your gearing high enough to allow top speeds but engine and tires robust enough to make it fun In the process