TH400 in place of TH350 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

krue · 08-03-2006, 10:17 PM

What do I need to go from a TH350 (that's slipping) to a TH400 in my 70 swb? Can I use my drive shaft? Do I need the electric kick down switch? I was going to rebuild a 700R4 but found this TH400 free and based on my immediate plans for the truck (heavy pulling) decided to take this route!

Longhorn Man · 08-03-2006, 10:29 PM

you'll need a new yoke, drive shaft mods (or take the whole saft from another truck) You'll need to move your cross member back...(exhaust mods may be needed) You don't NEED the electric kick down... it won't kill the tranny like on an overdrive, but you'll probably want it.
I think that's about it... don't forget a new converter and to flush your cooler REAL good.

krue · 08-04-2006, 02:22 PM

What is involved in modifying my driveshaft?

Longhorn Man · 08-04-2006, 03:46 PM

shortening it.
If for some odd reason you have a long shaft TH350, and you are going to a short shaft TH400 you'll need a longer shaft, but odds are you have a short TH350. (that's what's original in these rigs)
Pluss the yoke chainge.

krue · 08-04-2006, 10:22 PM

Sounds like a good time to get a one piece shaft.

Longhorn Man · 08-04-2006, 11:59 PM

agreed.

08-03-2006, 10:17 PM	#1
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,448	TH400 in place of TH350 What do I need to go from a TH350 (that's slipping) to a TH400 in my 70 swb? Can I use my drive shaft? Do I need the electric kick down switch? I was going to rebuild a 700R4 but found this TH400 free and based on my immediate plans for the truck (heavy pulling) decided to take this route! __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"

08-03-2006, 10:29 PM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: TH400 in place of TH350 you'll need a new yoke, drive shaft mods (or take the whole saft from another truck) You'll need to move your cross member back...(exhaust mods may be needed) You don't NEED the electric kick down... it won't kill the tranny like on an overdrive, but you'll probably want it. I think that's about it... don't forget a new converter and to flush your cooler REAL good.

08-04-2006, 02:22 PM	#3
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,448	Re: TH400 in place of TH350 What is involved in modifying my driveshaft? __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"

08-04-2006, 03:46 PM	#4
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: TH400 in place of TH350 shortening it. If for some odd reason you have a long shaft TH350, and you are going to a short shaft TH400 you'll need a longer shaft, but odds are you have a short TH350. (that's what's original in these rigs) Pluss the yoke chainge.

08-04-2006, 10:22 PM	#5
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,448	Re: TH400 in place of TH350 Sounds like a good time to get a one piece shaft. __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"

08-04-2006, 11:59 PM	#6
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: TH400 in place of TH350 agreed.



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