TH-400 conversion - The 1947 - Present Chevrolet & GMC Truck Message Board Network

timmy · 03-15-2002, 01:34 PM

I'm wanting convert my truck from a 3spd to a th-400. I've done an auto conversion before but it was a th-350. the question is the truck is a SWB, and has a 2pc driveshaft. Do i need to get a slip yoke or can i use the short one thats a bolt in version but not bolt it in and pull it out a little for sliding purposes

------------------
71 c-10 307/3 spd in the process of a makeover

*Fast68Chevy* · 03-15-2002, 01:52 PM

if its a bolt on output yoke then thats a giveaway sign that its out of a truck, how long is the overall length of the trans ? 34 or 29 ?
youll need to use a slip yoke version output yoke, from a donor car and weld that yoke onto your shaft, and adjust length of the shaft with cutter and welder and balance it, hopefully the tranny is long enough that you can make a one piece shaft out of a shaft out of a donor vehicle lie a 73-up truck with same axle as you have then you only have to change one end of the shaft still.(front)
you use a 67-72 auto trans member, and make sure the out put of the tranny is perfectly aligned with the pinion of the rear axle, or.... problems..
you know the rest, rad swap cooler lines linkage, can use 73-up if you dril the two holes for it in the top side of frame rail straight across from tranny shift shaft

good luck !

one legged lance · 03-15-2002, 04:16 PM

What happens if the output of the trans isn't perfectly lined up with the diff????? And is that horz or vert????
I just put a 700r4 in this week and eyeballed it but didn't check for pefect.
Thx,
1 Leg Lance

69 longhorn · 03-15-2002, 09:01 PM

A short tail 400T will be 11/16" longer than you saginaw 3spd,or a short tail 350T. this will requier cutting the shaft,& the crossmember will mount in a different place....but the holes should be in the frame. when you set the slip yolk up,& measure shaft lenght......slide it all the way in to bottom,mark it with a grease pencil,then pull it out 3/4-7/8". That is what you need for slip clearance....measure the shaft from that point. A link to dimentions.... http://www.tciauto.com/tech_info/trans_dims.htm

fastpan · 03-16-2002, 06:50 PM

I made a TH350 swap to a TH400 in my 72 C-10 and had to get a different cross member,also shortend my 2-piece drive shaft "1"inch on the front half.To balance it I drilled 2 small holes 180 degrees from one another,one at each end and put 1/2 a quart of 30 wt oil in it then plugged the holes with sheet metal screws and silicon,perfect fluid balance.

Slammed67 · 03-21-2002, 12:04 AM

ttt

------------------
Formerly know as: "GMC Under Construction" Current project: 1967 GMC shortbed/fleetside, 350/700R4, air bag suspension. Other vehicle of interest: 1957 Chevy Bel-Air 4dr hard top, 283/powerglide, lowered 3-1/2" in front and 2 inches in the rear.

Web Site: jaySpot.com AOL Screen Name: Slammed67GMC Location: Kansas City, MO

barn9 · 03-21-2002, 01:29 AM

You have issues to resolve wormy, er timmy!

jostrans68 · 03-21-2002, 01:53 AM

krossfiretim@aol.com
mail time I just logged on AOL and his address is ligit we may have to get a letter campain together..........

------------------
68 c20 in progress 327 TH400 tach dash Disc Brakes and soon 3.90 rear gears.. have many new parts now just need the time..... Sound Familar

[This message has been edited by jostrans68 (edited March 21, 2002).]

teeitup · 03-21-2002, 07:41 AM

take care of other stuff first!

lux hauler · 03-21-2002, 07:57 AM

he has mail

Jesse 67 c-10 · 03-21-2002, 11:56 AM

Never heard of using oil to balance a drive shaft, does it work pretty good? would 10w-30 work? I have to shorten my driveshaft 4" from my 5 speed swap so I may try this. Cool idea!
Jesse

------------------
Near Saskatoon, Saskatchewan, Canada. 67 c-10, Long fleet, Newly swapped front disks, 5 lug rear end, 327 v-8 with Vortech heads, edlbrock performer rpm air gap manifold, 1406 carb and comp XE 256 cam. Backed by a getrag 5 speed and 1 piece driveshaft. Finnally running, almost driving! www.geocities.com/chevy67jesse

*Fast68Chevy* · 03-21-2002, 12:23 PM

it depends on what th400 he is swapping to, some are 34" long ans some are 29 long, it depend son year and application, typically all the newer ones like late 70s and early 80s and up are 29"
the early 70s ones like int he big cars are 34"
you do not need a different crossmember, 67-72 trucks only have one version of auto crossmember, no matter what tranny, putting a newer tranny in 67-72 may require you to drill hole in between the existing two holes for the tranny mount to the xmember sine most all newer trannies use single stud style of mount unlike trucks did back then,

you cant use a bolt on yoke for the tranny poutput tail unless you have a lsip join style driveshaft, or you iwl have bg problems when you load down truck or go over bumps in road

one legged lance, i was talking about horizontal alignment, if the driveshaft doesnt go back straigh back to the axle pinion gear stib perfectly straight and if its off by too much then you can end up with broken mount or mounts and broken tranny bell housing because of the forcew of the drivetrain trying to straighten out when you put torque on it, IE when you drive.

and i dont reccommend drilling holes in a driveshaft, i owuld take shaft to a shop to have it balanced on machine, removing any metal by drilling holes in it is not what you should do, IMO

good luck

[This message has been edited by Fast68Chevy (edited March 21, 2002).]

bigcat · 03-21-2002, 12:38 PM

Pay your bills Timmy..... It's not fare to take the money and run.

03-15-2002, 01:34 PM	#1
timmy Registered User Join Date: Jun 2001 Location: rayville,la,us Posts: 65	TH-400 conversion I'm wanting convert my truck from a 3spd to a th-400. I've done an auto conversion before but it was a th-350. the question is the truck is a SWB, and has a 2pc driveshaft. Do i need to get a slip yoke or can i use the short one thats a bolt in version but not bolt it in and pull it out a little for sliding purposes ------------------ 71 c-10 307/3 spd in the process of a makeover __________________ 71 c-10 307/3 spd in the process of a makeover

03-15-2002, 09:01 PM	#4
69 longhorn Registered User Join Date: Aug 2001 Location: rock island,il,usa Posts: 5,382	A short tail 400T will be 11/16" longer than you saginaw 3spd,or a short tail 350T. this will requier cutting the shaft,& the crossmember will mount in a different place....but the holes should be in the frame. when you set the slip yolk up,& measure shaft lenght......slide it all the way in to bottom,mark it with a grease pencil,then pull it out 3/4-7/8". That is what you need for slip clearance....measure the shaft from that point. A link to dimentions.... http://www.tciauto.com/tech_info/trans_dims.htm __________________ http://community.webshots.com/user/hotrodhorn

03-21-2002, 12:04 AM	#6
Slammed67 Progress = 0% Join Date: Nov 2001 Location: Kansas City, MO Posts: 2,108	ttt ------------------ Formerly know as: "GMC Under Construction" Current project: 1967 GMC shortbed/fleetside, 350/700R4, air bag suspension. Other vehicle of interest: 1957 Chevy Bel-Air 4dr hard top, 283/powerglide, lowered 3-1/2" in front and 2 inches in the rear. Web Site: jaySpot.com AOL Screen Name: Slammed67GMC Location: Kansas City, MO __________________ Jason - '67 GMC swb \| '57 Bel-Air 4dr hardtop \| '56 210 4dr Wagon \| 2000 GMC Sierra

03-21-2002, 01:29 AM	#7
barn9 Half a bubble off! Join Date: Jun 2000 Location: Winfield, Ks, USA Posts: 5,588	You have issues to resolve wormy, er timmy! __________________ Just call me LB. '71 Cheyenne, 402BB, hauls blondes, brunettes, or redheads.

03-21-2002, 01:53 AM	#8
jostrans68 Jostrans68 Join Date: Mar 2001 Location: Bloomington indiana Posts: 1,182	krossfiretim@aol.com mail time I just logged on AOL and his address is ligit we may have to get a letter campain together.......... ------------------ 68 c20 in progress 327 TH400 tach dash Disc Brakes and soon 3.90 rear gears.. have many new parts now just need the time..... Sound Familar [This message has been edited by jostrans68 (edited March 21, 2002).] __________________ [CGTW Member former 67-72 now with a 96 silverado

03-15-2002, 01:52 PM	#2
Fast68Chevy Account Suspended Join Date: May 2000 Location: IL Posts: 0	if its a bolt on output yoke then thats a giveaway sign that its out of a truck, how long is the overall length of the trans ? 34 or 29 ? youll need to use a slip yoke version output yoke, from a donor car and weld that yoke onto your shaft, and adjust length of the shaft with cutter and welder and balance it, hopefully the tranny is long enough that you can make a one piece shaft out of a shaft out of a donor vehicle lie a 73-up truck with same axle as you have then you only have to change one end of the shaft still.(front) you use a 67-72 auto trans member, and make sure the out put of the tranny is perfectly aligned with the pinion of the rear axle, or.... problems.. you know the rest, rad swap cooler lines linkage, can use 73-up if you dril the two holes for it in the top side of frame rail straight across from tranny shift shaft good luck !

03-15-2002, 04:16 PM	#3
one legged lance Junior Member Join Date: Sep 2001 Location: Phx,Az USA Posts: 67	What happens if the output of the trans isn't perfectly lined up with the diff????? And is that horz or vert???? I just put a 700r4 in this week and eyeballed it but didn't check for pefect. Thx, 1 Leg Lance

03-16-2002, 06:50 PM	#5
fastpan Registered User Join Date: Mar 2002 Posts: 3	I made a TH350 swap to a TH400 in my 72 C-10 and had to get a different cross member,also shortend my 2-piece drive shaft "1"inch on the front half.To balance it I drilled 2 small holes 180 degrees from one another,one at each end and put 1/2 a quart of 30 wt oil in it then plugged the holes with sheet metal screws and silicon,perfect fluid balance.

03-21-2002, 07:41 AM	#9
teeitup Just like to part out trucks!! Join Date: Nov 2001 Location: Meriden, Ks-North of Topeka 10 miles Posts: 27,395	take care of other stuff first! __________________ 67 Chev swb stepside 4x4 283 4 speed SOLD 72 blazer 4x4 4 speed Cheyenne 72 GMC swb 4x4 fleet 4 speed, original paint 1958 Cameo (one of 1405 built, it was my dads) 2020 chevy Apex 4x4 crew cab 1969 Z28 with the 302 1980 chevy swb 4x4 1964 chevell Malibu SS 1976 K20, sold new originally out of my dads chevy dealership Members that I've met, over 200 probably closer to 300 in the 12 years I've been on this site, everyone I met "It was a pleasure"

03-21-2002, 07:57 AM	#10
lux hauler Psycho-billy Member Join Date: Jul 2001 Location: about 40 miles west of Cleveland, Ohio Posts: 2,591	he has mail __________________ '72 C-10 350 w/Lunati Voodoo cam (207/213, .437/.454), Performer intake, 625 Road Demon Jr. and Hooker headers. Support your community, support yourself. Buy local, buy American (or Canadian).

03-21-2002, 11:56 AM	#11
Jesse 67 c-10 Registered User Join Date: Feb 2000 Location: Edmonton, Alberta, Canada Posts: 599	Never heard of using oil to balance a drive shaft, does it work pretty good? would 10w-30 work? I have to shorten my driveshaft 4" from my 5 speed swap so I may try this. Cool idea! Jesse ------------------ Near Saskatoon, Saskatchewan, Canada. 67 c-10, Long fleet, Newly swapped front disks, 5 lug rear end, 327 v-8 with Vortech heads, edlbrock performer rpm air gap manifold, 1406 carb and comp XE 256 cam. Backed by a getrag 5 speed and 1 piece driveshaft. Finnally running, almost driving! www.geocities.com/chevy67jesse __________________ Edmonton, Alberta, 67 c-10, Long fleet, front disks, 5 lug rear end, 327 with Vortechs, edlbrock manifold, comp cams XE 256, 600cfm carb. Backed by a getrag 5 speed and 1 piece driveshaft. 1993 Dihatsu Hijet Jumbo cab 4x4, currently converting to battery electric power.

03-21-2002, 12:23 PM	#12
Fast68Chevy Account Suspended Join Date: May 2000 Location: IL Posts: 0	it depends on what th400 he is swapping to, some are 34" long ans some are 29 long, it depend son year and application, typically all the newer ones like late 70s and early 80s and up are 29" the early 70s ones like int he big cars are 34" you do not need a different crossmember, 67-72 trucks only have one version of auto crossmember, no matter what tranny, putting a newer tranny in 67-72 may require you to drill hole in between the existing two holes for the tranny mount to the xmember sine most all newer trannies use single stud style of mount unlike trucks did back then, you cant use a bolt on yoke for the tranny poutput tail unless you have a lsip join style driveshaft, or you iwl have bg problems when you load down truck or go over bumps in road one legged lance, i was talking about horizontal alignment, if the driveshaft doesnt go back straigh back to the axle pinion gear stib perfectly straight and if its off by too much then you can end up with broken mount or mounts and broken tranny bell housing because of the forcew of the drivetrain trying to straighten out when you put torque on it, IE when you drive. and i dont reccommend drilling holes in a driveshaft, i owuld take shaft to a shop to have it balanced on machine, removing any metal by drilling holes in it is not what you should do, IMO good luck [This message has been edited by Fast68Chevy (edited March 21, 2002).]

03-21-2002, 12:38 PM	#13
bigcat Registered User Join Date: Jan 2002 Location: Grayslake, Illinois Posts: 8	Pay your bills Timmy..... It's not fare to take the money and run.



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.