3spd on the tree swap to a TH400 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Trifelynn · 09-26-2004, 03:45 PM

I started a thread in the blazer forum, and someone said there was an FAQ for it. I looked through and didn't see it. Thought maybe someone here has already done the swap and could help out. Any pics/documents/words of advice would be great....

Transmissions are something I have yet to get into, so you could say I was Layman's little brother...so, even the littlest thing will help...Here are the things I was told and know already.

I have a new Crossmember, and the linkage...
I was told that I need to make sure that I have the little pivot point thing that mounts to the crossmember...

anything else anyone can help with...I am a visual learner, so any pics would be great...thanks

Lenny

Harold Shepard · 09-26-2004, 05:24 PM

Turbo 400 takes a different frame bracket than the th350. If you can not find the th400 bracket you can use the th350 bracket if you don't mind drilling new holes in the frame. All frames have the location holes in place already, so no big deal on that part. You will need a different driveshaft or get yours shortened as well as a new tranny yoke. The holes for the cross member are already in place, just jack up thr trans and locate the holes you need to use for your application. You will need cooler lines and either a rad with built in trans cooler or a dedicated cooler mouted in front of your existing rad. You will also need a new flex plate and a different starter nose to complete the swap. I know this sounds like a lot but it is not too bad, and goes pretty quick. Hope this helps, Harold

Trifelynn · 09-26-2004, 06:10 PM

Thanks Harold...

It doesn't sound like too much, I guess I just don't know what some of these things are, and where to get them...

sorry for my ignorance, but I want to do it myself, rather than pay someone to do it, so I can learn...

PanelDeland · 09-26-2004, 07:31 PM

You need to get yourself a manual.It will help you understand the names of the parts and give you a visual on where they go.If you want the cheapest manual available send for a LMC catalog.It's free and has great parts drawings though their prices are a bit high.(BB vendors will do you a better deal).In thge meantime try your local parts store, they should have a Haynes or Chiltons manual to help you figure out which parts are what.Usually runs about $20.00 Amellican.

Harold Shepard · 09-26-2004, 07:36 PM

Yeah It is better to learn to do something than pay to have it done, that way you can look back and say I did that. As far as parts, you have got some of the important ones. Post on the parts board for the th400 frame bracket, check with Tim Christian about the trans cooler lines - about $50 plus you don't have to bend them, the GM dealer for the TH400 trans yoke- about $60. If your starter is old, prob. should replace it anyway $50 + bolts $5 and shim pack $3. Trans cooler $30-$50 bucks and finally Motormite flexplate- $30 plus you need to figure out what rear end gear you have in order to get your speedo gear right- trans shop or dealer is are the people to talk to about this (choices are 3.07 or 3.73 rear gears). Tell parts guys that you have 350 engine w/ th400 need new flexplate and starter and you want to see what they have in aux. trans coolers. Tell dealer or trans shop what rear end you have and they will (should ) be able to give or get the correct trans drive gear and driven gear (located in the trans tail housing- should be about $15 or so). Hope this helps. Harold

09-26-2004, 03:45 PM	#1
Trifelynn Registered User Join Date: May 2004 Location: Williston, North Dakota Posts: 469	3spd on the tree swap to a TH400 I started a thread in the blazer forum, and someone said there was an FAQ for it. I looked through and didn't see it. Thought maybe someone here has already done the swap and could help out. Any pics/documents/words of advice would be great.... Transmissions are something I have yet to get into, so you could say I was Layman's little brother...so, even the littlest thing will help...Here are the things I was told and know already. I have a new Crossmember, and the linkage... I was told that I need to make sure that I have the little pivot point thing that mounts to the crossmember... anything else anyone can help with...I am a visual learner, so any pics would be great...thanks Lenny __________________ Always looking for a 2wd blazer

09-26-2004, 06:10 PM	#3
Trifelynn Registered User Join Date: May 2004 Location: Williston, North Dakota Posts: 469	Thanks Harold... It doesn't sound like too much, I guess I just don't know what some of these things are, and where to get them... sorry for my ignorance, but I want to do it myself, rather than pay someone to do it, so I can learn... __________________ Always looking for a 2wd blazer

09-26-2004, 07:31 PM	#4
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,993	You need to get yourself a manual.It will help you understand the names of the parts and give you a visual on where they go.If you want the cheapest manual available send for a LMC catalog.It's free and has great parts drawings though their prices are a bit high.(BB vendors will do you a better deal).In thge meantime try your local parts store, they should have a Haynes or Chiltons manual to help you figure out which parts are what.Usually runs about $20.00 Amellican. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

09-26-2004, 05:24 PM	#2
Harold Shepard Registered User Join Date: May 2004 Location: Canton North Carolina Posts: 466	Turbo 400 takes a different frame bracket than the th350. If you can not find the th400 bracket you can use the th350 bracket if you don't mind drilling new holes in the frame. All frames have the location holes in place already, so no big deal on that part. You will need a different driveshaft or get yours shortened as well as a new tranny yoke. The holes for the cross member are already in place, just jack up thr trans and locate the holes you need to use for your application. You will need cooler lines and either a rad with built in trans cooler or a dedicated cooler mouted in front of your existing rad. You will also need a new flex plate and a different starter nose to complete the swap. I know this sounds like a lot but it is not too bad, and goes pretty quick. Hope this helps, Harold

09-26-2004, 07:36 PM	#5
Harold Shepard Registered User Join Date: May 2004 Location: Canton North Carolina Posts: 466	Yeah It is better to learn to do something than pay to have it done, that way you can look back and say I did that. As far as parts, you have got some of the important ones. Post on the parts board for the th400 frame bracket, check with Tim Christian about the trans cooler lines - about $50 plus you don't have to bend them, the GM dealer for the TH400 trans yoke- about $60. If your starter is old, prob. should replace it anyway $50 + bolts $5 and shim pack $3. Trans cooler $30-$50 bucks and finally Motormite flexplate- $30 plus you need to figure out what rear end gear you have in order to get your speedo gear right- trans shop or dealer is are the people to talk to about this (choices are 3.07 or 3.73 rear gears). Tell parts guys that you have 350 engine w/ th400 need new flexplate and starter and you want to see what they have in aux. trans coolers. Tell dealer or trans shop what rear end you have and they will (should ) be able to give or get the correct trans drive gear and driven gear (located in the trans tail housing- should be about $15 or so). Hope this helps. Harold



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