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#1 |
Registered User
Join Date: Apr 2003
Location: missouri city, tx
Posts: 4,486
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driveshaft difference?
i want to put a th400 behind my 350, i have a th350... do i have to modify the driveshaft or is it the same length and all?
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70 longbed 496/th400/Ford 9" |
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#2 |
Resident Curmudgeon
![]() Join Date: Dec 1999
Location: NH
Posts: 6,664
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The slip yolk is splined differently but I think the lengths are nearly identical
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Currently on or near the homestead: 67 Chevy SWB 2WD stepside 350/3 on tree (Pat's) 67 GMC SWB 2WD Fleet 402/auto (Brian's under construction) 67 Chevy 3/4 ton 2WD 402/auto (Business Hauler) 67 Chevy 1 ton dually 2WD 396/4 speed (Former business hauler, Needs TLC) 68 Chevy 1/2 ton Suburban 2WD 250 six/3 on tree (Brian's Needs TLC) 70 Chevy 3/4 ton 4WD 350/4 speed (Pat's - Disguised as a 68 GMC) 71 Chevy SWB stepside (Crushed by tree - parts donor) 72 Chevy 3/4 ton 4WD (Parts donor) 72 Chevy 3/4 ton 4WD Suburban (Parts Donor) 72 GMC 3/4 ton 4WD 292 six/4 speed (Mine - Disguised as a 67 GMC) 81 GMC 4WD Dually Dump Body 350/4 speed (Business Hauler) 82 Camaro Z/28 355/Super T-10 (Pat's toy) 93 Caprice 9C1 (Brian's Cop Car) 02 Toyota Camry (Reliable but a souless steel and plastic hulk) 2011 2SS RS Camaro M6 Factory Hurst Shifter ![]() Maybe I need to sell some of this crap ![]() Yet another Bozo with a sawz-all |
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#3 |
Senior Member
![]() Join Date: Feb 2003
Location: WIS
Posts: 1,752
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driveshaft length
It also matters if your th350 had a short or long tailshaft.
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#4 |
Registered User
![]() Join Date: Nov 2003
Location: San Diego, CA
Posts: 62
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TCI has a good chart that shows the dimensions for various tailshaft lengths on the TH-350 & TH-400. Also, the TH-400 uses an electrically operated kick down rather than a TV cable.
http://www.tciauto.com/tech_info/trans_dims.htm
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Be wary of the light at the end of the tunnel....It might be a gorilla holding a flashlight! 71 Blazer, ex-4WD...Bought it that way 55 GMC 55 Belair 2dr HT 67 El Camino |
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#5 |
Black 72 Chevy
Join Date: May 2002
Location: Los Angeles, California
Posts: 662
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SS55
How you connect the electrically operated kick down? A.P. |
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#6 |
Registered User
![]() Join Date: Jan 2001
Location: Katy, TX...but the love of my life resides in Dublin,OH.
Posts: 1,408
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trans crossmember is different also
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#7 |
Registered User
Join Date: Apr 2003
Location: missouri city, tx
Posts: 4,486
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the crossmember is different? how come when they sell them they sell them as automatic crossmembers? are you sure theyre different?
and cpne.... the spline yolk, what is that? im not very familiar with driveshafts. is this swap goign to be alot more than i think it is? can someone who was done this tell me what they had to do?
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70 longbed 496/th400/Ford 9" |
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#8 |
Resident Curmudgeon
![]() Join Date: Dec 1999
Location: NH
Posts: 6,664
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As far as I've been able to determine the auto xmember (supports) the rear of the tranny is the same for a th350 or th400. It sits slightly further back because the overall length of the 400 is a littler longer.
The yolk is the end of the driveshaft that slides into the end of the tranny.
__________________
Currently on or near the homestead: 67 Chevy SWB 2WD stepside 350/3 on tree (Pat's) 67 GMC SWB 2WD Fleet 402/auto (Brian's under construction) 67 Chevy 3/4 ton 2WD 402/auto (Business Hauler) 67 Chevy 1 ton dually 2WD 396/4 speed (Former business hauler, Needs TLC) 68 Chevy 1/2 ton Suburban 2WD 250 six/3 on tree (Brian's Needs TLC) 70 Chevy 3/4 ton 4WD 350/4 speed (Pat's - Disguised as a 68 GMC) 71 Chevy SWB stepside (Crushed by tree - parts donor) 72 Chevy 3/4 ton 4WD (Parts donor) 72 Chevy 3/4 ton 4WD Suburban (Parts Donor) 72 GMC 3/4 ton 4WD 292 six/4 speed (Mine - Disguised as a 67 GMC) 81 GMC 4WD Dually Dump Body 350/4 speed (Business Hauler) 82 Camaro Z/28 355/Super T-10 (Pat's toy) 93 Caprice 9C1 (Brian's Cop Car) 02 Toyota Camry (Reliable but a souless steel and plastic hulk) 2011 2SS RS Camaro M6 Factory Hurst Shifter ![]() Maybe I need to sell some of this crap ![]() Yet another Bozo with a sawz-all |
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#9 |
Registered User
Join Date: Apr 2003
Location: missouri city, tx
Posts: 4,486
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so the driveshaft will have to be modified for the th400 to work?
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70 longbed 496/th400/Ford 9" |
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#10 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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I am 99% positive the TH400 is longer than the Th350.
If so, the drive shaft will have to b modified, and if I am wron, then all you'll need is a new slip yolk on your front U-joint. |
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#11 |
Registered User
![]() Join Date: Jan 2001
Location: Katy, TX...but the love of my life resides in Dublin,OH.
Posts: 1,408
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Well I couldn't get the 400 to bolt up to the th350 cross member I had to take the one out of the truck the 400 came out of. Maybe I have some weird set up... but they looked different also. I was having a hard time getting it to line up and once I changed them.... zip went right in.
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#12 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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Quick question, why you want to go through the hassle of the swap? Is your TH350 dead, or are you pushing over 400 horses?
I just don't see much of a point in putting in a TH400 otherwise....But that's just me. |
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#13 |
Registered User
![]() Join Date: Nov 2003
Location: San Diego, CA
Posts: 62
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As for the kick down switch, the originals were either mounted on a bracket at the carb and was actuated by the carb throttle lever or was mounted to the accelerator pedal on bracket by the pedal. Aftermarket companies sell switch assemblies to do this function. It is just a normally open switch that is closes when you stick your foot in it.
In my experience, the crossmembers were the same, but did have to be moved because of the trans mount locations. You will definately need to change yokes as the TH-400 is a lot bigger and splined differently. The driveshaft will need to be shorter if going to a TH-400 from a TH-350
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Be wary of the light at the end of the tunnel....It might be a gorilla holding a flashlight! 71 Blazer, ex-4WD...Bought it that way 55 GMC 55 Belair 2dr HT 67 El Camino |
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#14 |
Registered User
Join Date: Apr 2003
Location: missouri city, tx
Posts: 4,486
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my th350 is on its last leg. and before i start driving the truck, ill need a transmission that shifts
![]() thanks suicide-d for your experience. seems like you answered my question... but, if all i had to do was move the crossmember and change the yolk, that would great and not that hard. seems like everyone had a different experience...
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70 longbed 496/th400/Ford 9" |
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#15 |
Watch out for your cornhole !
![]() Join Date: Jun 2003
Location: Azle, Texas
Posts: 14,162
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The crossmember is the same. Just use the mount off of your old TH350. The 400 will require the crossmember to be slid on the frame, but that's why your frame has all of those holes in it.
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#16 |
Registered User
Join Date: May 2003
Location: Shreveport LA
Posts: 3,170
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If both trannys are the short-tail versions, the length should be almost the same.
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