? Th400 vs th350 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jostrans68 · 12-28-2002, 09:26 PM

I know the th400 sucks more hp. Will it be a noticable Diiference if I drop to a th350.. My 64 327 is 325 hp I have got a drive line and a th350 is it worth it. I have to pull the rebuilt th400 as it has sit too long and developed a leak or two, I await all opinions jack

mikep · 12-28-2002, 09:34 PM

If you can notice a 15 HP difference then you will notice a difference. The TH400 is a stronger transmission although the TH350 runs a lot of these trucks. Ive blown up a few TH350's but I drive like an idiot. You rpobably wouldnt break it.

If you want to get rid of the TH400 after you change it out I'd like a shot at it.

Jwill41 · 12-28-2002, 09:38 PM

I have had the same th400 in mine for 14-15 years. Love it. It is geared real well for my truck. What do you mean by "th400 sucks more hp" What makes it different from a th350?

da-burb · 12-28-2002, 09:41 PM

I've read that it takes 20hp more to turn a th400 than a th350.

mikep · 12-28-2002, 09:46 PM

Theres more internal rotating mass to spin up. Its not as bad as a Ford C6/C4 difference but your still looking at 15 HP or so it takes to run the TH400 compared to a Turbo 350. TH350 can be built to handle a lot of power . Ive just never had one built that way. BTW dont believe a transmission shop that tells you they are building the TH350 (or 700R4 for that matter) to handle X amount of power unless you actually witness them building the transmission with the specialty parts needed. Its not just the clutches. No offense to you transmission shop guys but tranny shops will rob you blind!

mikep · 12-28-2002, 09:48 PM

Especially the 700 R4 !

crazy longhorn · 12-28-2002, 10:03 PM

Im going dual elect fans to offset the extra power that my 400 turbo takes. If you really want a tough trans, keep the 400.......my thoughts, if I decide to go OD it will get a Gear vendors on the back

jmanz69 · 12-28-2002, 10:28 PM

If you have a good TH-350 it will handle your 325 HP no problem. My 327 was at least 325 when I had it installed behind my junkyard TH-350 and I drove the crap out of it for 4 years before putting the truck in storage. It's a great transmission. The TH-400 is awsome too, but if you don't have a lot of HP you don't need it. Get the 400 rebuilt and have it as a spare or sell it. The drag racers love them. Just my 2 cents

Jefe · 12-28-2002, 11:29 PM

I've got a TH350 behind a 412 small block pumping out about 450hp. Run it at the track all the time...never had a problem with it yet. Only thing done to the tranny is a regular fluid/filter change, 3000 stall, and strip shift kit. Works great!!

Douglas.

mikep · 12-29-2002, 12:28 AM

Iv'e blown 6 of them up . 2 with gears actually rupturing through the case.

3 were behind a Pontiac 455 in a transam with a 2400 stall converter. 2 in a 79 blazer with 350 HP small block and 1 in a 69 camaro with a 400HP 350. I have never blown up a TH 400 and I have run as many of them as I have TH 350's.

12-28-2002, 09:26 PM	#1
jostrans68 Jostrans68 Join Date: Mar 2001 Location: Bloomington indiana Posts: 1,182	? Th400 vs th350 I know the th400 sucks more hp. Will it be a noticable Diiference if I drop to a th350.. My 64 327 is 325 hp I have got a drive line and a th350 is it worth it. I have to pull the rebuilt th400 as it has sit too long and developed a leak or two, I await all opinions jack __________________ [CGTW Member former 67-72 now with a 96 silverado

12-28-2002, 09:34 PM	#2
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	If you can notice a 15 HP difference then you will notice a difference. The TH400 is a stronger transmission although the TH350 runs a lot of these trucks. Ive blown up a few TH350's but I drive like an idiot. You rpobably wouldnt break it. If you want to get rid of the TH400 after you change it out I'd like a shot at it. __________________ No truck :-(

12-28-2002, 09:38 PM	#3
Jwill41 Registered User Join Date: Aug 2002 Location: Farmers Branch, Tx Posts: 1,009	I have had the same th400 in mine for 14-15 years. Love it. It is geared real well for my truck. What do you mean by "th400 sucks more hp" What makes it different from a th350? __________________ http://www.picturetrail.com/jwill41 67 1/2 ton GMC short step side 68 1/2 ton Chevy long fleet side 72 1/2 ton Chevy Suburban 99 1/2 ton Chevy Suburban founder (and only member) of the primer/clearcoat club

12-28-2002, 09:41 PM	#4
da-burb "Ochre Ogre" Join Date: Apr 2000 Location: Springfield, MN Posts: 3,558	I've read that it takes 20hp more to turn a th400 than a th350. __________________ Bowtie Truck Stop Inc. Mid-West GM Truck Restoration Parts Supplier Your Key Parts, Auto Metal Direct, Dynacorn, and Goodmark dealer. like us @ www.facebook.com/BowtieTruckStop 1971 C-10 Suburban (Ochre) 1971 K-10 Suburban (Ochre) 1972 C-10 Suburban (Ochre) 1972 K-20 Suburban (Yellow- that just aint right!) Springfield, Minnesota 56087

12-28-2002, 09:46 PM	#5
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	Theres more internal rotating mass to spin up. Its not as bad as a Ford C6/C4 difference but your still looking at 15 HP or so it takes to run the TH400 compared to a Turbo 350. TH350 can be built to handle a lot of power . Ive just never had one built that way. BTW dont believe a transmission shop that tells you they are building the TH350 (or 700R4 for that matter) to handle X amount of power unless you actually witness them building the transmission with the specialty parts needed. Its not just the clutches. No offense to you transmission shop guys but tranny shops will rob you blind! __________________ No truck :-(

12-28-2002, 09:48 PM	#6
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	Especially the 700 R4 ! __________________ No truck :-(

12-28-2002, 10:03 PM	#7
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,402	Im going dual elect fans to offset the extra power that my 400 turbo takes. If you really want a tough trans, keep the 400.......my thoughts, if I decide to go OD it will get a Gear vendors on the back __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

12-28-2002, 10:28 PM	#8
jmanz69 Careful, they attack... Join Date: Aug 2001 Location: Waterford, MI, USA Posts: 1,107	If you have a good TH-350 it will handle your 325 HP no problem. My 327 was at least 325 when I had it installed behind my junkyard TH-350 and I drove the crap out of it for 4 years before putting the truck in storage. It's a great transmission. The TH-400 is awsome too, but if you don't have a lot of HP you don't need it. Get the 400 rebuilt and have it as a spare or sell it. The drag racers love them. Just my 2 cents

12-28-2002, 11:29 PM	#9
Jefe Registered User Join Date: Jul 2000 Location: Chandler, Arizona, USA Posts: 299	I've got a TH350 behind a 412 small block pumping out about 450hp. Run it at the track all the time...never had a problem with it yet. Only thing done to the tranny is a regular fluid/filter change, 3000 stall, and strip shift kit. Works great!! Douglas.

12-29-2002, 12:28 AM	#10
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	Iv'e blown 6 of them up . 2 with gears actually rupturing through the case. 3 were behind a Pontiac 455 in a transam with a 2400 stall converter. 2 in a 79 blazer with 350 HP small block and 1 in a 69 camaro with a 400HP 350. I have never blown up a TH 400 and I have run as many of them as I have TH 350's. __________________ No truck :-(



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