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Jeff's72C10* · 04-10-2018, 07:17 PM

Hi all, recently picked up my 3rd 67-72 pu.

I purchased a 72 LB Custom Deluxe (pic in avatar). Truck has a 350 4bbl, TH350 tranny and factory air (currently inop). Question I have is how much trouble would it be to swap the TH350 for a 400? Brackets, braces etc. The last 2 I had (69SB & 72 Cheyenne LB) had the 400 transmission. Is it worth it to swap or just leave as is. Thx in advance.

**jocko** · 04-10-2018, 07:35 PM

I'd leave as is with a 350 eng personally. If you soup it up, maybe worth an upgrade, but if you're going to spend the $ on an upgrade, recommend a beefed up overdrive trans for lower highway rpm, unless you currently have a 3.07 in the back - in which case it may not really be necessary. For a driver that you aren't doing burnouts in (IF you aren't doing burnouts in it, that is

), a TH350 is a sound, reliable trans, not worth the effort to swap in my opinion. If you are doing burnouts, I'd still wait, if it fails, then that means it's time for a swap - so, maybe I should say it's not worth it to pre-emptively swap it as it may not be necessary.

Jeff's72C10* · 04-10-2018, 10:12 PM

Quote:

Originally Posted by jocko

I'd leave as is with a 350 eng personally. If you soup it up, maybe worth an upgrade, but if you're going to spend the $ on an upgrade, recommend a beefed up overdrive trans for lower highway rpm, unless you currently have a 3.07 in the back - in which case it may not really be necessary. For a driver that you aren't doing burnouts in (IF you aren't doing burnouts in it, that is

), a TH350 is a sound, reliable trans, not worth the effort to swap in my opinion. If you are doing burnouts, I'd still wait, if it fails, then that means it's time for a swap - so, maybe I should say it's not worth it to pre-emptively swap it as it may not be necessary.

Thanks you sir for the info. It does have a 12 bolt rear end but not sure what gears. Some one through the years was kind enough to put a chrome glove box door on, so no SPID.

truckster · 04-10-2018, 11:15 PM

I've run a TH350 behind a built Olds 455. They're plenty stout, and they have less drag than the TH400. I see no reason to change it.

Oh, I forgot to say... Welcome to the board!

Coley · 04-11-2018, 02:33 PM

To my understanding the fuel mileage with a TH400 will drop off as well.
I think this is due to the fact that they take more hp to run perhaps.....if that matters?

Regardless tho', like the guys said....I'd stick the TH350..its a great transmission, tough and well suited to these trucks in a 1/2 ton with the 350.

just my two cents.

Coley

Jeff's72C10* · 04-11-2018, 10:41 PM

Quote:

Originally Posted by Coley

To my understanding the fuel mileage with a TH400 will drop off as well.
I think this is due to the fact that they take more hp to run perhaps.....if that matters?

Regardless tho', like the guys said....I'd stick the TH350..its a great transmission, tough and well suited to these trucks in a 1/2 ton with the 350.

just my two cents.

Coley

Appreciate all the input guys. Thank you

04-10-2018, 07:17 PM	#1
Jeff's72C10* Active Member Join Date: Mar 2018 Location: Del Rio Posts: 166	New here Hi all, recently picked up my 3rd 67-72 pu. I purchased a 72 LB Custom Deluxe (pic in avatar). Truck has a 350 4bbl, TH350 tranny and factory air (currently inop). Question I have is how much trouble would it be to swap the TH350 for a 400? Brackets, braces etc. The last 2 I had (69SB & 72 Cheyenne LB) had the 400 transmission. Is it worth it to swap or just leave as is. Thx in advance. __________________ Previous C10's 69 SB CST - sold 72 Cheyenne Super LB - sold

04-10-2018, 07:35 PM	#2
jocko Senior Member Join Date: Oct 2009 Location: Godley, TX Posts: 17,984	Re: New here I'd leave as is with a 350 eng personally. If you soup it up, maybe worth an upgrade, but if you're going to spend the $ on an upgrade, recommend a beefed up overdrive trans for lower highway rpm, unless you currently have a 3.07 in the back - in which case it may not really be necessary. For a driver that you aren't doing burnouts in (IF you aren't doing burnouts in it, that is ), a TH350 is a sound, reliable trans, not worth the effort to swap in my opinion. If you are doing burnouts, I'd still wait, if it fails, then that means it's time for a swap - so, maybe I should say it's not worth it to pre-emptively swap it as it may not be necessary.

04-10-2018, 11:15 PM	#4
truckster Registered User Join Date: Jan 2001 Location: Orem, Utah Posts: 7,989	Re: New here I've run a TH350 behind a built Olds 455. They're plenty stout, and they have less drag than the TH400. I see no reason to change it. Oh, I forgot to say... Welcome to the board! __________________ I have sworn upon the altar of God, eternal hostility against every form of tyranny over the mind of man. - Thomas Jefferson Last edited by truckster; 04-11-2018 at 12:12 AM.

04-11-2018, 02:33 PM	#5
Coley Registered User Join Date: Oct 2011 Location: Victoria, B.C Posts: 3,794	Re: New here To my understanding the fuel mileage with a TH400 will drop off as well. I think this is due to the fact that they take more hp to run perhaps.....if that matters? Regardless tho', like the guys said....I'd stick the TH350..its a great transmission, tough and well suited to these trucks in a 1/2 ton with the 350. just my two cents. Coley __________________ ....for some men, there is experience, skill and effort....for the others...there is visa and UPS LOL 1966 Chevy 1/2 ton (Florida- Red/white) 1972 Chevy 1/2 ton (California- Blue/white) 2005 Chevy Silverado HD2500/Duramax 2000 Dodge Ram 1500



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