TH400 to 3-4 Speed??? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

67chevemall · 01-26-2005, 02:57 PM

What manual tran would replace a TH400 in a 78 C-20?
Use the same mounts, fly wheel, and drive shaft?
I'm looking for the easy swap!

I'd like to buy some linkage too!

badone07 · 01-26-2005, 03:47 PM

Should be a direct swap with a SM465 4 spd. You would still have to change flexplate to flywheel. Clutch linkage(z-bar type) or swap to hydraulics. Add a pilot bearing to the crank. Hole in the tunnel for the shifter(toploader type trans). Then swapping the steering column. Driveshaft should be fine. Just depends on if the 400 has a slip in yoke or bolt on, to whether or not you would have to remove the slip yoke from the universal joint.

For performance type trans, I would look for something else though and do the necessary mods for fitment.

67chevemall · 01-26-2005, 03:55 PM

Thanks John! What other trans will work? And what kind of mods would you need?
I've never heard of a SM465 4 spd? Any pics or links to this trany?

67chevemall · 01-26-2005, 04:13 PM

This was interesting!
http://www.lightruck.com/other_overu...tion.asp#GM2WD
Did a google search seems like good trany?

badone07 · 01-26-2005, 04:40 PM

For a non-performance truck, besides the SM465, I would probably only do the necessary mods to install an NV4500, 5 spd. However, I would convert to an aftermarket hydraulic clutch setup. Then move trans bracket and deal with altering the driveshaft. My current pickup came with a SM465, but I only use it tow and hopefully soon to convert to 4x4.

I've owned a couple of trucks that had SM465's. If getting a used one, I would try to test drive it first. The only problems I've seen is the synchros going and the tranny popping out of gear, unless the shifter was manually held in place. are usually easy to find and fairly cheap. Just a little on the heavy side. One person can install them without a jack though. You can make other trannies work, but you said the "easiest swap." Which also most likely would be the cheapest as well.

edit... Here is another recent post.
http://67-72chevytrucks.com/vboard/s....php3?t=136923

67chevemall · 01-26-2005, 07:55 PM

SM465 it is! I gotta try this granny gear out!

Any pics of the linkage I would need to install for the clutch as.

I have 2 TH400's for sale that are great condition!$for project!

*1FaastC10* · 01-26-2005, 09:05 PM

SM465 WILL NOT directly replace a TH400. it is however a bolt in for your truck, but requiring a bolt in trans hump and a hole to be cut in the floor for clutch linkage(or one in the firewall if you are fortunate enough to find a hydraulic clutch setup) your driveshaft will have to be lengthened.

badone07 · 01-27-2005, 12:16 AM

I have done the reverse of this swap a few times, but not recently. Have a 3.5k mile 400th sitting on floor in garage, that I decided not to use. The hole in the tunnel yes, as well as hole in the floor for stock clutch linkage set up. Mine doesn't have a bolt in tunnel with a SM465. If I do go the NV4500 route, I won't be using a stock hydraulic pedal setup, unless I stumbled upon one in a junkyard. Haven't looked yet anyway. Just as easy to mount an aftermarket racing clutch pedal/mc setup to the firewall or adapting it to the stock mount. Fabricating a bracket off the bellhousing and using either a push or pull slave, depending on fork clearances. Sure I have a spare AFCO mount sitting on a shelf. Or just using a hydraulic throwout bearing. Then running a braided line between the two. Simple, basic racing setup.

If snow isn't too deep around my truck (leg still in a brace), I'll measure both and get a few pics for you also.

The turbo 400 from bellhousing face to mount is 27 15/16. Maybe someone in a warmer climate can get the measurement for the sm465. Snow is too high around my truck.

**Captkaos** · 01-27-2005, 12:34 AM

Don't forget you need the complete pedal assembly for this too.

67chevemall · 01-28-2005, 02:26 AM

ttt
who else wants to flip their TH400/350?

*1FaastC10* · 01-28-2005, 05:19 PM

mine is in the process, all i have to do is cut the hole in the floor under the bolt in hump, and slide the trans and transfer case in. i went with a factory hydraulic clutch setup, but it was a PITA to find it.

badone07 · 01-28-2005, 11:43 PM

Quote:

Originally Posted by 1FaastC10

mine is in the process, all i have to do is cut the hole in the floor under the bolt in hump, and slide the trans and transfer case in. i went with a factory hydraulic clutch setup, but it was a PITA to find it.

The bolt-in tunnel for a k series or converting to 4x4. Not for a c series 2wd. 67chevemall is doing a c-20.

I'm going to look around tomorrow in a junkyard for a stock hydraulic setup, while looking for something else. I'll bring a tape as well. They are are lifted off the ground. Can't crawl around on the ground just yet. Which all will depend on the weather.

badone07 · 01-30-2005, 02:38 AM

Sorry 67 chevemall couldn't get the info today. My day got screwed up beyond my control.
http://207.44.196.117/vboard/showthread.php3?t=138300

67chevemall · 01-30-2005, 10:50 AM

Thats' one bad day!

u2slow · 02-01-2005, 12:33 AM

Quote:

Originally Posted by badone07

The bolt-in tunnel for a k series or converting to 4x4. Not for a c series 2wd. 67chevemall is doing a c-20.

Not quite. I have a tunnel from a '78 c20 4-spd truck. I took it out myself. The tower on the top of the SM465 is quite tall. You would be putting a *large* hole in the tunnel of a low-hump cab to make it fit

badone07 · 02-01-2005, 03:40 AM

Quote:

Originally Posted by u2slow

Not quite. I have a tunnel from a '78 c20 4-spd truck. I took it out myself. The tower on the top of the SM465 is quite tall. You would be putting a *large* hole in the tunnel of a low-hump cab to make it fit

I've owned 2 (1 presently) and know of 3 other c-series that came stock with the sm465, factory boot and the low tunnel. I've also seen them the same in a few fairly large junkyards. Not doubting your truck but I'll look check for others like it this weekend.

u2slow · 02-01-2005, 10:37 AM

I should mention that around 81-82 they eliminated the removable tunnel, but still carried on with a high and low hump profile. I have trucks with all three types.

I'll see if I can get a pic of that '78 tunnel posted tonight.

u2slow · 02-03-2005, 03:16 PM

The '78 2wd SM465 tunnel:

The 81/82-up "high hump" on SM465 or 4wd trucks.

badone07 · 02-03-2005, 06:11 PM

Thanks for posting the pics. I was interested in the humps in the past but only converted from manual to auto. Wonder if Suburbans were/are similar. I'm still going to look at others over the weekend, while they are sitting there. Below is my 84 with boot and without. Looks lower than your linked 4wd hump, by boots height and positioning.
Yes, I know I have a hose clamp on it. Had a problem with the roll pins working loose.

u2slow · 02-03-2005, 06:43 PM

That hump is the same as the red hump in the link (my crewcab). I have a 2" body lift... that's why the boots look squished and the shifter a little short.

My Burb floor is lower, and it's a 2wd w/TH400. I have that '78 hump for when I decide to change it over to manual

01-26-2005, 02:57 PM	#1
67chevemall Registered User Join Date: Apr 2003 Location: NB Posts: 3,367	TH400 to 3-4 Speed??? What manual tran would replace a TH400 in a 78 C-20? Use the same mounts, fly wheel, and drive shaft? I'm looking for the easy swap! I'd like to buy some linkage too! __________________ 1968 Chevy C10 307 3ott fleetside 1967 Chevy C/10 V8, 3spd, fleetside lwb.Sold 1967 Chev C/10 step, 383, M21. SOLD

01-26-2005, 03:47 PM	#2
badone07 Project 2 Resume Join Date: May 2004 Location: Jim Thorpe, PA Posts: 884	Should be a direct swap with a SM465 4 spd. You would still have to change flexplate to flywheel. Clutch linkage(z-bar type) or swap to hydraulics. Add a pilot bearing to the crank. Hole in the tunnel for the shifter(toploader type trans). Then swapping the steering column. Driveshaft should be fine. Just depends on if the 400 has a slip in yoke or bolt on, to whether or not you would have to remove the slip yoke from the universal joint. For performance type trans, I would look for something else though and do the necessary mods for fitment. __________________ John 1984 C30 Chevy Crew Cab Dually 1998 Jeep Cherokee 4x4 2004 Chevy Trailblazer 4x4 (wife's) 1970 Mustang FB fully tubed (getting 521 BBF & powerglide) 1978 Nova 2dr (going BBCaddy & S.P. th400) 1984 Monte SS (circle track car)

01-26-2005, 04:40 PM	#5
badone07 Project 2 Resume Join Date: May 2004 Location: Jim Thorpe, PA Posts: 884	For a non-performance truck, besides the SM465, I would probably only do the necessary mods to install an NV4500, 5 spd. However, I would convert to an aftermarket hydraulic clutch setup. Then move trans bracket and deal with altering the driveshaft. My current pickup came with a SM465, but I only use it tow and hopefully soon to convert to 4x4. I've owned a couple of trucks that had SM465's. If getting a used one, I would try to test drive it first. The only problems I've seen is the synchros going and the tranny popping out of gear, unless the shifter was manually held in place. are usually easy to find and fairly cheap. Just a little on the heavy side. One person can install them without a jack though. You can make other trannies work, but you said the "easiest swap." Which also most likely would be the cheapest as well. edit... Here is another recent post. http://67-72chevytrucks.com/vboard/s....php3?t=136923 __________________ John 1984 C30 Chevy Crew Cab Dually 1998 Jeep Cherokee 4x4 2004 Chevy Trailblazer 4x4 (wife's) 1970 Mustang FB fully tubed (getting 521 BBF & powerglide) 1978 Nova 2dr (going BBCaddy & S.P. th400) 1984 Monte SS (circle track car) Last edited by badone07; 01-26-2005 at 05:02 PM.

01-26-2005, 07:55 PM	#6
67chevemall Registered User Join Date: Apr 2003 Location: NB Posts: 3,367	SM465 it is! I gotta try this granny gear out! Any pics of the linkage I would need to install for the clutch as. I have 2 TH400's for sale that are great condition!$for project! __________________ 1968 Chevy C10 307 3ott fleetside 1967 Chevy C/10 V8, 3spd, fleetside lwb.Sold 1967 Chev C/10 step, 383, M21. SOLD

01-27-2005, 12:16 AM	#8
badone07 Project 2 Resume Join Date: May 2004 Location: Jim Thorpe, PA Posts: 884	I have done the reverse of this swap a few times, but not recently. Have a 3.5k mile 400th sitting on floor in garage, that I decided not to use. The hole in the tunnel yes, as well as hole in the floor for stock clutch linkage set up. Mine doesn't have a bolt in tunnel with a SM465. If I do go the NV4500 route, I won't be using a stock hydraulic pedal setup, unless I stumbled upon one in a junkyard. Haven't looked yet anyway. Just as easy to mount an aftermarket racing clutch pedal/mc setup to the firewall or adapting it to the stock mount. Fabricating a bracket off the bellhousing and using either a push or pull slave, depending on fork clearances. Sure I have a spare AFCO mount sitting on a shelf. Or just using a hydraulic throwout bearing. Then running a braided line between the two. Simple, basic racing setup. If snow isn't too deep around my truck (leg still in a brace), I'll measure both and get a few pics for you also. The turbo 400 from bellhousing face to mount is 27 15/16. Maybe someone in a warmer climate can get the measurement for the sm465. Snow is too high around my truck. Attached Images __________________ John 1984 C30 Chevy Crew Cab Dually 1998 Jeep Cherokee 4x4 2004 Chevy Trailblazer 4x4 (wife's) 1970 Mustang FB fully tubed (getting 521 BBF & powerglide) 1978 Nova 2dr (going BBCaddy & S.P. th400) 1984 Monte SS (circle track car) Last edited by badone07; 01-28-2005 at 03:44 PM.

01-26-2005, 03:55 PM	#3
67chevemall Registered User Join Date: Apr 2003 Location: NB Posts: 3,367	Thanks John! What other trans will work? And what kind of mods would you need? I've never heard of a SM465 4 spd? Any pics or links to this trany?

01-26-2005, 04:13 PM	#4
67chevemall Registered User Join Date: Apr 2003 Location: NB Posts: 3,367	This was interesting! http://www.lightruck.com/other_overu...tion.asp#GM2WD Did a google search seems like good trany?

01-26-2005, 09:05 PM	#7
1FaastC10 Account Suspended Join Date: Oct 2002 Location: Elkhart, IN Posts: 6,400	SM465 WILL NOT directly replace a TH400. it is however a bolt in for your truck, but requiring a bolt in trans hump and a hole to be cut in the floor for clutch linkage(or one in the firewall if you are fortunate enough to find a hydraulic clutch setup) your driveshaft will have to be lengthened.

01-27-2005, 12:34 AM	#9
Captkaos www.73-87chevytrucks.com Join Date: Dec 1999 Location: Birmingham, AL Posts: 6,935	Don't forget you need the complete pedal assembly for this too. __________________ Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com

01-28-2005, 02:26 AM	#10
67chevemall Registered User Join Date: Apr 2003 Location: NB Posts: 3,367	ttt who else wants to flip their TH400/350? __________________ 1968 Chevy C10 307 3ott fleetside 1967 Chevy C/10 V8, 3spd, fleetside lwb.Sold 1967 Chev C/10 step, 383, M21. SOLD

01-28-2005, 05:19 PM	#11
1FaastC10 Account Suspended Join Date: Oct 2002 Location: Elkhart, IN Posts: 6,400	mine is in the process, all i have to do is cut the hole in the floor under the bolt in hump, and slide the trans and transfer case in. i went with a factory hydraulic clutch setup, but it was a PITA to find it.

01-30-2005, 02:38 AM	#13
badone07 Project 2 Resume Join Date: May 2004 Location: Jim Thorpe, PA Posts: 884	Sorry 67 chevemall couldn't get the info today. My day got screwed up beyond my control. http://207.44.196.117/vboard/showthread.php3?t=138300 __________________ John 1984 C30 Chevy Crew Cab Dually 1998 Jeep Cherokee 4x4 2004 Chevy Trailblazer 4x4 (wife's) 1970 Mustang FB fully tubed (getting 521 BBF & powerglide) 1978 Nova 2dr (going BBCaddy & S.P. th400) 1984 Monte SS (circle track car)

01-30-2005, 10:50 AM	#14
67chevemall Registered User Join Date: Apr 2003 Location: NB Posts: 3,367	Thats' one bad day!

02-01-2005, 10:37 AM	#17
u2slow Web Wheeler Join Date: Jan 2000 Location: BC, Canada, eh? Posts: 388	I should mention that around 81-82 they eliminated the removable tunnel, but still carried on with a high and low hump profile. I have trucks with all three types. I'll see if I can get a pic of that '78 tunnel posted tonight. __________________ '66 C10 longstep - Clifford equiped '84 C20 Suburban 6.2L - awaiting 4x4 conversion '91 V3500 Crewcab - awaiting diesel swap

02-03-2005, 03:16 PM	#18
u2slow Web Wheeler Join Date: Jan 2000 Location: BC, Canada, eh? Posts: 388	The '78 2wd SM465 tunnel: The 81/82-up "high hump" on SM465 or 4wd trucks. __________________ '66 C10 longstep - Clifford equiped '84 C20 Suburban 6.2L - awaiting 4x4 conversion '91 V3500 Crewcab - awaiting diesel swap



Register or Log In To remove these advertisements.

02-03-2005, 06:11 PM	#19
badone07 Project 2 Resume Join Date: May 2004 Location: Jim Thorpe, PA Posts: 884	Thanks for posting the pics. I was interested in the humps in the past but only converted from manual to auto. Wonder if Suburbans were/are similar. I'm still going to look at others over the weekend, while they are sitting there. Below is my 84 with boot and without. Looks lower than your linked 4wd hump, by boots height and positioning. Yes, I know I have a hose clamp on it. Had a problem with the roll pins working loose. Attached Images __________________ John 1984 C30 Chevy Crew Cab Dually 1998 Jeep Cherokee 4x4 2004 Chevy Trailblazer 4x4 (wife's) 1970 Mustang FB fully tubed (getting 521 BBF & powerglide) 1978 Nova 2dr (going BBCaddy & S.P. th400) 1984 Monte SS (circle track car) Last edited by badone07; 02-03-2005 at 06:14 PM.

02-03-2005, 06:43 PM	#20
u2slow Web Wheeler Join Date: Jan 2000 Location: BC, Canada, eh? Posts: 388	That hump is the same as the red hump in the link (my crewcab). I have a 2" body lift... that's why the boots look squished and the shifter a little short. My Burb floor is lower, and it's a 2wd w/TH400. I have that '78 hump for when I decide to change it over to manual __________________ '66 C10 longstep - Clifford equiped '84 C20 Suburban 6.2L - awaiting 4x4 conversion '91 V3500 Crewcab - awaiting diesel swap

Register or Log In To remove these advertisements.