6066 (1960-1966) GMC Truck Club

6066 (1960-1966) GMC Truck Club (https://6066gmcclub.com/index.php)

- GMC V6 and V12 Engines (https://6066gmcclub.com/forumdisplay.php?f=9)

- - 1967 351e (https://6066gmcclub.com/showthread.php?t=47895)

Quote:

Originally Posted by sclor (Post 51139)

Dog:
What tranny do you have now and how many RPM's are you turning on the highway at 55?
Regards,
Steve
New Orleans

I am running a T400 right now...as far as RPMs i have NO idea I need to get a tachometer

Two questions. 1/2 ton or 3/4 ton, and what gear ratio. Barry

Quote:

Originally Posted by BarryGMC (Post 51142)

Two questions. 1/2 ton or 3/4 ton, and what gear ratio. Barry

3/4 ton....I don't know my gear ratio..imma have t o find out :headscratch:

I just saw your pic on the 67-72 site. Cool truck. Post a pic of the spid if it's still on the glovebox door. Second look at the rear end cover there may be a tag still on it, if it's there get the numbers off it. I am guessing 4.10. Since you did the trans work already I would suggest 3.54 gears in the rear. All of my gmc 3/4 tons get this ratio, and I find it a good compromise. Barry

There are several ways to drop your highway RPMs. From cheapest to most expensive:

1. taller rear tires
2. swap your 4.10 or 4.56 for 3.54 or 3.73 rear end ratio
3. swap your TH400 for a 4L80, 6L80, or one of their variations
4. install a Gearvendors overdrive behind the trans

Quote:

Originally Posted by BarryGMC (Post 51144)

the glove box door has been replaced...i looked at the pumkin and i got a pat # and another # that looks like .3 30255 :headscratch:

So no little tag under a cover bolt. No spid. Time to jack up a wheel and put her in neutral and count how many times the driveline turns to one wheel turn. Now if it has a powerlock it may not turn easily. It will be half of your actual ratio. 4.10 would give 2 turns on the driveline, one turn of the wheel. Now if your handy with your wrenching skills I can walk you through a RP swap that you can do for less than 300.00 bucks if it's a 4.10 a hundred more if it's a 4.56. Barry

Hi,

I guess I am a bit late, but here is my take. If your 351 V6 is running well, why change. I can understand changing, if your engine is "shot". However, as others have said, that 351 (if taken care of) is good for 300 - 500 thousand miles.

Parts for these V6 engines are axially easy to find. If you look, you will find all parts. It just takes a bit of looking. Yes, the parts are not available "over the counter" at your local auto parts store. But who cares. I have a 62 305, now 401 V6 that I rebuilt 7 years ago. It is my daily driver. I even have "stockpiled" enough parts to rebuild it again. But, funny thing, I have never used any of these "stockpiled parts". The thing just keeps running. As others have said, if you treat this V6 with "reasonable care" it will run forever. It axially needs to be run, to last.

The best thing you can do with one of these V6's is to gear it so it can "keep up with" today's traffic. And return reasonable fuel mileage. With my 62/401 I get 13-14 around town & 17-18 highway. Average: 15-16. To get this mileage you must keep the RPM'S around 17-1800.

Good Luck & Keep that V6
Rick

got a 351 w/5spd in my yard right now! $200 for engine, $200 for tranny, plenty of parts!!!!

You already have an automatic so I would go with a later model automatic like a 4L60(same as 700R4) 4L60E or the stronger 4L80E overdrive GM automatic transmissions, the later two will require a stand alone computer.