454 + TH400 + 4.11 POSI = no freeway

[Phorbes]

Just picked up my first C10. It's a gorgeous truck, black in color, long bed and in all around excellent condition. Previous owner lived downtown so he had no use for freeway driving and I'm a little outside of town and would certainly like to be able to drive on the freeway.

Long story short, I took the truck home (on the freeway) and I could barely make myself go above 60MPH because the motor was SCREAMING!

I know it's not damaging anything, just burning fuel. I want this truck to be cruiser, to help pick up supplies at home depot and haul the dogs around in. Not a show truck or a drag racing truck, just a good all around usable truck.

Right now I have the standard 265/70/15 tire sizes and I know I could put much larger (in diameter) tires on to help bring down the RPM. There's no Tach on the dash so I'm not sure what kind of RPM I'm at right now but I would have to guess 60MPH is at least 3k+

Question is, what do I do?

Do I take out the rear end and put lower gears? I know the POSI is excellent and bulletproof and worth a pretty penny so I'm sad to do that.

Should I just slap on some super large tires on the rear?

Should I get a different tranny with more gears? TH400 runs good, gear shifting is a little sloppy, but I'm not sure if that's normal or concerning? I have an 86 C10 I had purchased to work on and its sitting in my garage that has a TH350 on it but I believe both of them are just 3 speed transmissions so that really would't help to swap would it?

I don't mind spending another $1000-$1500 to make it work. I'm new to the old truck world or even carbureted motors. I'm a BMW guy and have always wanted an old American work horse.

So that's that, what should I do?

Thanks for the help in advance!!!

[toolboxchev]

Put a 3.73 or 3.54 ring and pinion set in there. I would go with the 3.54 you have plenty of power to push those gears. Rather not to expensive either.

[Jason Banks]

I would say you want an overdrive transmission swap TH700R4 and maybe a rear gear swap also. Depending on the POSI you have there might be a lower gear available.

[davepl]

The BEST solution is overdrive (as in an overdrive transmission). That's not cheap for you, because you'd need a 4L80E (about $1800 rebuilt) and a controller (about 600) and a speed drive tailhousing or electronic box (another 700).

It's what I did in my big block 1970 truck, and it's great.

Now if you could find used parts (like a working used 4L80E for about $500) it'd be a lot cheaper.

Another option is the 200-4R which can be built fairly strong, is about the same length, and still has a mechanical speedo drive. That's what I started with but it only lived about 50 miles in my truck (had lived for 10,000 in my car, don't know what the rebuilder messed up!).

I think the build 200-4R is still my preferred option because you don't need ANY electronics.

[truckster]

Rear gears. With a 454 you don't need a 4.11 unless you're drag racing. My Z28 has 2.72 gears in it and can still light up the tires. I'd look at maybe a 3.23 ratio.

[RINC]

My 69 C-20 has a Gear Vendor's OD unit in it.

TH400 an 4:10 R&P.

Make for some nice freeway cruising.

Just throwing that out there as another option.

[Phorbes]

Local ad here from a gentleman who has a 4L80 just rebuilt (0 miles) for $1200. What's the controller you speak of?

Originally Posted by davepl

The BEST solution is overdrive (as in an overdrive transmission). That's not cheap for you, because you'd need a 4L80E (about $1800 rebuilt) and a controller (about 600) and a speed drive tailhousing or electronic box (another 700).

It's what I did in my big block 1970 truck, and it's great.

Now if you could find used parts (like a working used 4L80E for about $500) it'd be a lot cheaper.

Another option is the 200-4R which can be built fairly strong, is about the same length, and still has a mechanical speedo drive. That's what I started with but it only lived about 50 miles in my truck (had lived for 10,000 in my car, don't know what the rebuilder messed up!).

I think the build 200-4R is still my preferred option because you don't need ANY electronics.

Posted via Mobile Device

[Phorbes]

Does this seem like a fair deal?

https://austin.craigslist.org/pts/6180299217.html

Originally Posted by Jason Banks

I would say you want an overdrive transmission swap TH700R4 and maybe a rear gear swap also. Depending on the POSI you have there might be a lower gear available.

Posted via Mobile Device

[mrein3]

Originally Posted by Phorbes

snip

Long story short, I took the truck home (on the freeway) and I could barely make myself go above 60MPH because the motor was SCREAMING!

I know it's not damaging anything, just burning fuel. I want this truck to be cruiser, to help pick up supplies at home depot and haul the dogs around in. Not a show truck or a drag racing truck, just a good all around usable truck.

snip

Don't be so sure you aren't damaging anything. I'm running a temporary engine right now. A very used 307 that is powering its third vehicle while I deal with a self inflicted issue in my 383.

A few weeks ago I took it to the MN State Fair Grounds to meet da-burb who sells new and used truck parts. (I purchased a repop long bed bedside that except for the little angle iron piece welded to the front of the rear stake pocket that I had go move up fit like a glove and looks awesome).

I debated with myself over whether I should take the freeway (70mph for 20 minutes or so) or stick to the back roads. I ended up on the freeway. Turbo 350, stock height tires, 3.73s, 3500 rpms on the tach. I monitored engine temp, tranny temp, and oil pressure all the way down. As the oil heated up the pressure slowly lowered but it stayed above the 1/4 mark - where the tired 350 that shared the same gauge lived.

I get off the freeway, rpms down to in-town levels. OIL PRESSURE BOTTOMS OUT!!! Long story short I think I wiped a lobe on the cam.

I would address the freeway rpms or just avoid it altogether. Those 4.11s with that super low 700r4 first gear might be fun off the line.

[KQQL IT]

4.11 and a 700 low gear is good for about a crosswalk.

Ran a 427 in a C-60 @ 3200 forever didn't seem to care to much.

I'd get a gearvendor or 3.54 ring for it

[clay68c10]

For similar $ you could go Gear Vendors or a manual TKO500. fun but $2500-$3k

For cheap, 3.23/3.07 gears

[mattfranklin]

In the mean time run a heavier oil (20W50?) to keep your viscosity up or avoid the freeway. ;-)

[kwmech]

You'll have to change the posi when you go to a 'taller' gear set. 3.42 ratio will work just fine with the tire size. You could even go with a 3.08. The big block will have plenty of power to pull through the gears. And please don't waste your time and money with a 700....... I don't care what anybody says about building them tougher to last behind a big block. Simply stated they don't last. If you want to go the replacing the transmission route, put in a 4L80E and never worry about it again. Another bullet proof solution without a controller is the Gear Vendor (as previously mentioned), it will bolt right on the back of your 400, a little bit of wiring and shortening of your driveshaft and you're done. They are a tough unit and will last quite a while also.

[ElKotze]

The cheapest way would probably be to swap your rear gears, but I'm almost sure you have to change your carrier to a series3 . Series3 posi carriers are about $450, get a ring and pinion (308, for example) for $200 and I would also recommend a master overhaul kit for $200, comes with new bearings and different shims. That's exactly what I did, now I'm cruising 70 mph @ 2600 rpm. Your 454 won't have any trouble pushing whatever gear you want to put in.

[DarkFlounder]

The cheap/easiest would be to swap the rear gears. But I think you'd be happier with an overdrive, either an add-on or a trans swap.

[trac209]

Another vote to swap the gears. I swapped a 3.73 for a 3.07 and it was easy cheap and made that truck way easier to drive at higher speeds. I have a Sbc and it still has plenty of get up and go.

[BossHogg69]

I'd put a 3.08 in it and be done. Especially with the torque of a 454. I daily drive a '65 Chevy Bel Air, multiple 12 hour round trips from Little Rock to Ft. Worth, TX - sbc/Th350/3.08's and it cruises just fine with 28" tall rear tires (275/60/15) runs 70mph at 2600rpm and still gets 16-17 mpg. Obviously a 454 won't get that mileage, but it would still cruise just fine.

If that $1k is burning a hole in your pocket you could even slap a posi in with the new gears.

[Alex]

I believe the BBC equipped trucks came stock with 3.07 gears with the TH400. I'm not sure why several are saying get the 3.08 as this was installed in passenger cars while 3.07s were installed in trucks. Correct me on this one if I'm wrong. Anyways, that's what I have in mine and it runs just fine at 70-75 mph.

[71threequarterton]

I'm leaning towards this too: http://www.gearvendors.com/index.html

[kwmech]

Originally Posted by Alex

I'm not sure why several are saying get the 3.08 as this was installed in passenger cars while 3.07s were installed in trucks.

All of the replacement sets that I've seen for either the truck or car are 3.08.. Besides, 1 percent of a change is not a big deal

[AnotherWs6]

3.07's in my 396 Suburban and it runs well. Never wanting for more gear and cruises at 70 no problem. It's the cheapest, easiest way to do it. You could keep what you have in case you go overdrive later, or sell it to help fund your new setup.

Not sure why you'd have to lose your posi carier when switching to taller gears.

[kwmech]

Originally Posted by AnotherWs6

Not sure why you'd have to lose your posi carier when switching to taller gears.

Larger pinion requires the ring gear be moved to the left some for mounting of the ring gear to get the proper set-up. Case is offset some

[zachste]

I have 4.11 gears on my truck with a SBC and TH350, and agree, it's not fun on the highway at all.

[leddzepp]

Put a 3.07 rear end and be done with it. I just yanked the 3.73 out of my 68 and swapped in a 3.07 rear, drives like a dream now on the freeway. You don't need a posi for anything other than to say "I've got a posi!"

[RustyBucket]

Bet you could find a complete rear end assembly on Craigslist. There are usually several at any given time 'round here. Open carrier 3.08 rears were pretty common and still are.... not much money. Bolt it in and cruise.