Thinking about swapping to auto trans:

[Greasey Harley]

I was thinking about collecting parts to swap my '68 c10 to Colum shift auto trans. It is currently a small block V8/SM455 truck.
I'll NEVER own another 700r4 and I don't want any electronics in my truck.
This seems to limit my options to th350 and th400 ...I think.
in '68 the only AT option would have been th400, and I just happen to have a good useable unit in my shop. I know the history and trust the trans.
That being said, I would prefer a th350, as I ain't drag racing and they tend to get a little better mileage, and have a slightly better gear spread.

Okay, so finally to my question
Install the good used th400, or get a fresh th350. Advantages, disadvantages?

I got some time here, just thinking out loud.
Interested in input.
-Russ

[RustyBucket]

Bolt that th400 in and ride.... I've abused several of them badly and couldn't break 'em. Had them in a variety of trucks & cars: '68 C20, '79 Silverado, '68 442, '67 SS Chevelle.
Just had the 700r4 in my '71 GMC rebuilt & it works "funny".... I'm puckered up whether I've got the dread TV cable adjusted right.

[BRL]

I would go with the 400.

It ain't that much heavier, it is stronger, and you already have it.

I put a TH350 in mine, but I already had it from another truck, and I saved $$$.

[gmc684x4]

I read an car article about how well a beefed up 200r can live behind a 1000 hp motor
Not sure on the costs

Route I have chosen is 4l80e to mate up to the 5.3 lm7 motor I have

https://www.hotrod.com/articles/ccrp...mission-build/

[lil hoodlum]

As you stated, in 1968 the optional automatic transmission was the TH400. If you had a 1968 327 with automatic, it would have come with the TH400. I don't have any experience with the TH400, but that would be my choice as well. Good luck in whatever you decide.

[ChevyRacefan]

Are you driving this truck enough that the under 1 mpg difference in fuel use is going to make or break you?
You have the th400, run it.

[factorystock]

In '68, the autos were the powerglide and the 400. The 350 came out in '69. I would use the 400, since you already have it. Start collecting all the parts necessary, its never fast and easy finding all the original parts and linkages if you don't have a complete donor in your yard.

[tim_mc]

Just curious why you wouldn't want a 700R4 over a TH350/400. '84 and later versions have a better 30-spline input shaft and '87 and up versions are considered to be solid transmissions.

I swapped out my TH350 with a rebuilt later model '92 700R4 and love it. It has an earlier valve body with hydraulic lock-up kit for the converter, so no solenoid to power.

However, if you have a good TH400 in the shop and are OK with a 3 speed then I would use what you have.

[Greasey Harley]

Originally Posted by tim_mc

Just curious why you wouldn't want a 700R4 over a TH350/400. '84 and later versions have a better 30-spline input shaft and '87 and up versions are considered to be solid transmissions.

I swapped out my TH350 with a rebuilt later model '92 700R4 and love it. It has an earlier valve body with hydraulic lock-up kit for the converter, so no solenoid to power.

However, if you have a good TH400 in the shop and are OK with a 3 speed then I would use what you have.

I've just had bad luck with the 700r4's, and I'm not putting electronics in my fifty year old truck. I like old trucks because of their simplicity, not in spite of it.

[Old Money]

i have a 72 c-10 up hill 350. it came with t 400. 8 miles per gallon,uphill,downhill,going around corners,coasting or wide open throttle. at 350 will cost you in the begining.but better gas mileage. the 400 will break the bank at the gas pump. i put in a MD8, gas mileage increased to 12.6 mph.

[ChevyRacefan]

Originally Posted by Old Money

i have a 72 c-10 up hill 350. it came with t 400. 8 miles per gallon,uphill,downhill,going around corners,coasting or wide open throttle. at 350 will cost you in the begining.but better gas mileage. the 400 will break the bank at the gas pump. i put in a MD8, gas mileage increased to 12.6 mph.

Something is very very wrong if you gained 4.6mpg. going from a th400 to a th350.

[68bowtie]

My 700r4 is an early version (1981 I think), it has no electronics. Just the mechanical kick down cable. I totally get your position, just didn’t know if you were aware that was an option.

[ChevyRacefan]

Originally Posted by 68bowtie

My 700r4 is an early version (1981 I think), it has no electronics. Just the mechanical kick down cable. I totally get your position, just didn’t know if you were aware that was an option.

Many are scared off by the 7004r and 2004r because of the t.v. cable.
Because if you don't see it correctly, and add the correct geometry to the carb linkage. They burn up.
Do it right and they will go 200k miles without an issue.
Not using the lock up converter clutch and driving around town in 4th kill them.
Like all transmissions heat in fluid is the enemy. and using o/d without the lock up converter clutch generates a ton of heat.

[MARKDTN]

You don't need any electronics to run a 700R4. My '83 K20 was stock with Q-jet and 700R4. It has a wire for converter lockup and such but there is nothing solid-state involved-just switches an 12V no different than kickdown on a TH400. Choice of TH350 or TH400 that you know, I'd go TH400. But in your case I would get a quality built 700R4 by someone who knows them and adjust the TV cable before it starts the first time. Then drive it. The Q-jet brackets for the TV cables are out there in trucks, vans, MonteCarlo, Impala, Camaro....

My '83 K20 went about 80K on the original transmission pulling trailers and hauling before the front pump died. Got a GM reman with updates after that.

[Greasey Harley]

Originally Posted by MARKDTN

You don't need any electronics to run a 700R4. My '83 K20 was stock with Q-jet and 700R4. It has a wire for converter lockup and such but there is nothing solid-state involved-just switches an 12V no different than kickdown on a TH400. Choice of TH350 or TH400 that you know, I'd go TH400. But in your case I would get a quality built 700R4 by someone who knows them and adjust the TV cable before it starts the first time. Then drive it. The Q-jet brackets for the TV cables are out there in trucks, vans, MonteCarlo, Impala, Camaro....

My '83 K20 went about 80K on the original transmission pulling trailers and hauling before the front pump died. Got a GM reman with updates after that.

I will never own another 700r4. Ain't happenin'.
calling around to price out fresh th350's, still on the fence.
In the mean time watching the parts board for bits and pieces.

[clay68c10]

Any chance for using a newer OD manual? It's like a built in anti-theft device and more fun to drive.
T5, NV4500, TKO