turbo 350 to th400 swap

driller1720 · 02-26-2005, 04:15 PM

can i put a th400 in when i took out a th350. it is in a 4x4 with a 203 transfer case? I DIDN`T SAY I WAS PUTTING IN A BIG BLOCK. I have a 350 engine with a 350 tranny, i was woundering about putting in a 400 tranny.

warrenp · 02-26-2005, 04:28 PM

yep!!
th400 is alot better any way, thats exactly the same conversion i will be preforming as soon as i can.
ohh the 203 transfer is a great transfer should be by the looks of then
huge thats what i have also.
but realize they are all time 4 wheel drive!!!!!
the trans fer is alwast going!!!
not good for gas!
some one was telling me summit racing offers a kit to fix that for around $60
then basicly it will be about the same as a NP 205

chevynut · 02-28-2005, 06:53 AM

trans. will bolt to engine but every thing else will be fun,first real problem the rear shaft (or tail shaft) on the 400 will be larger,the trans. longer ( cut and extend drive shafts) relocate crossmember,no passing gear because of going from a cable to electric---- why change,you can beef up the 350 it should be more than enough

warrenp · 02-28-2005, 04:26 PM

even a beefy th350 will not hold up to a big block.
gm never put a turbo 350 on a big block stock!
there's a reasion for that.

chevynut · 03-01-2005, 07:08 AM

We've built hundreds of them with no problem,one day a customer came back with the complaintthat his trans. just quit pulling,we towed it in to the shop pulled the transfer case and noticed a real problem,the rear shaft was wrong into. We called the customer,he said he was just riding down the road at normal speed and it happened.Later on that day he called back and told us that he found out what really happened,his sons were driving it and got together in the parking lot with a few friends tring to burn all four tires. truck had detroit lockers and 36 tires. we have built 350s for some who are pushing over 500hp without complaints......

chevynut · 03-01-2005, 07:24 AM

However we do admit a 400 will be better suited if touque is what you are after and as far as full time 4wd,locking hubs and weilding the spider gears in transfer or ordering converson kit will solve that

warrenp · 03-01-2005, 07:40 AM

not trying to be rude really!
but your the 1st person to say that.
i have talked to two tranny shops and people on the net with experiance using the th350 on big block applications they all claim they will not hold up.

personally i have alwasy been a big fan of the th350 until my reciant resrch.
kinda depressed now.
becasue i have 2 of them. the one in my truck now is starting to go.
thats my own experiance.

as i said befor "gm never put a turbo 350 on a big block stock!
there's a reasion for that."
granted it was for stock applications
if you can convince me other wise that a th350 is a good trans i will consider rebuilding my to beef it up.
my i need alot of proof.

chevynut · 03-02-2005, 07:25 AM

We likewise are not tring to be rude nor smart,we are ever learning,but the transmission business has been our profession for over 24 yrs. we've been in the machanic business 10 yrs prior. We have built many streetrods and currently own and play with many, it,s a long list, we were into the the 4/4s for a while and still own a couple. I can only speak of what I know and experence. What I would like to know is the complant on this trans. A few years ago we installed 350s in two chevelles,one a 70 SS 454,the other a 71 SS was a 350 engine and one of my employees installed a 454,we went thru the 350 at the time,we gave them heck,no one should treat any car like we did.We did tear the posi.rear out of it,but the trans. held up. A couple of years ago we built another 350 for a guy to put in a camaro with a 500+hp 383 with nos,and he did manage to tear it up,and when we went back into the trans we found the forwand drum cracked where the front shaft was splined in,when we told him this is rare,then he told us he was neutralizing the car to 4000 rpms then slaming it to 1st,no wonder.Like I said,we have only good to say about the 350s.We bought a 70 SS 454 monte carlo, in which we still own,that some one had removed the 400 and replaced it with a 350 and we did remove the 350 and went back to the 400. But in the case of the 4/4 unless you want to spend the money and the time you will never know the difference. If you do decide to keep it in you would benifit by installing red line clutches , a shift kit and cooler.

02-26-2005, 04:15 PM	#1
driller1720 Junior Member Join Date: Feb 2005 Location: northern california Posts: 1	turbo 350 to th400 swap can i put a th400 in when i took out a th350. it is in a 4x4 with a 203 transfer case? I DIDN`T SAY I WAS PUTTING IN A BIG BLOCK. I have a 350 engine with a 350 tranny, i was woundering about putting in a 400 tranny. Last edited by driller1720; 03-04-2005 at 07:06 AM.

03-02-2005, 07:25 AM	#8
chevynut Full Member Join Date: Feb 2005 Posts: 33	We likewise are not tring to be rude nor smart,we are ever learning,but the transmission business has been our profession for over 24 yrs. we've been in the machanic business 10 yrs prior. We have built many streetrods and currently own and play with many, it,s a long list, we were into the the 4/4s for a while and still own a couple. I can only speak of what I know and experence. What I would like to know is the complant on this trans. A few years ago we installed 350s in two chevelles,one a 70 SS 454,the other a 71 SS was a 350 engine and one of my employees installed a 454,we went thru the 350 at the time,we gave them heck,no one should treat any car like we did.We did tear the posi.rear out of it,but the trans. held up. A couple of years ago we built another 350 for a guy to put in a camaro with a 500+hp 383 with nos,and he did manage to tear it up,and when we went back into the trans we found the forwand drum cracked where the front shaft was splined in,when we told him this is rare,then he told us he was neutralizing the car to 4000 rpms then slaming it to 1st,no wonder.Like I said,we have only good to say about the 350s.We bought a 70 SS 454 monte carlo, in which we still own,that some one had removed the 400 and replaced it with a 350 and we did remove the 350 and went back to the 400. But in the case of the 4/4 unless you want to spend the money and the time you will never know the difference. If you do decide to keep it in you would benifit by installing red line clutches , a shift kit and cooler. Last edited by chevynut; 03-02-2005 at 10:07 AM.

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02-26-2005, 04:28 PM	#2
warrenp Banned Join Date: Oct 2004 Location: maine Posts: 49	yep!! th400 is alot better any way, thats exactly the same conversion i will be preforming as soon as i can. ohh the 203 transfer is a great transfer should be by the looks of then huge thats what i have also. but realize they are all time 4 wheel drive!!!!! the trans fer is alwast going!!! not good for gas! some one was telling me summit racing offers a kit to fix that for around $60 then basicly it will be about the same as a NP 205

02-28-2005, 06:53 AM	#3
chevynut Full Member Join Date: Feb 2005 Posts: 33	trans. will bolt to engine but every thing else will be fun,first real problem the rear shaft (or tail shaft) on the 400 will be larger,the trans. longer ( cut and extend drive shafts) relocate crossmember,no passing gear because of going from a cable to electric---- why change,you can beef up the 350 it should be more than enough

02-28-2005, 04:26 PM	#4
warrenp Banned Join Date: Oct 2004 Location: maine Posts: 49	even a beefy th350 will not hold up to a big block. gm never put a turbo 350 on a big block stock! there's a reasion for that.

03-01-2005, 07:08 AM	#5
chevynut Full Member Join Date: Feb 2005 Posts: 33	We've built hundreds of them with no problem,one day a customer came back with the complaintthat his trans. just quit pulling,we towed it in to the shop pulled the transfer case and noticed a real problem,the rear shaft was wrong into. We called the customer,he said he was just riding down the road at normal speed and it happened.Later on that day he called back and told us that he found out what really happened,his sons were driving it and got together in the parking lot with a few friends tring to burn all four tires. truck had detroit lockers and 36 tires. we have built 350s for some who are pushing over 500hp without complaints......

03-01-2005, 07:24 AM	#6
chevynut Full Member Join Date: Feb 2005 Posts: 33	However we do admit a 400 will be better suited if touque is what you are after and as far as full time 4wd,locking hubs and weilding the spider gears in transfer or ordering converson kit will solve that

03-01-2005, 07:40 AM	#7
warrenp Banned Join Date: Oct 2004 Location: maine Posts: 49	not trying to be rude really! but your the 1st person to say that. i have talked to two tranny shops and people on the net with experiance using the th350 on big block applications they all claim they will not hold up. personally i have alwasy been a big fan of the th350 until my reciant resrch. kinda depressed now. becasue i have 2 of them. the one in my truck now is starting to go. thats my own experiance. as i said befor "gm never put a turbo 350 on a big block stock! there's a reasion for that." granted it was for stock applications if you can convince me other wise that a th350 is a good trans i will consider rebuilding my to beef it up. my i need alot of proof.