LS TH400 help please

[72GreenMonster]

1. Current stock 402 400 trans. What is the stock stall and do i need to upgrade torque converter? If so which converter would i buy or is a matching bolt tc compatible with the older trans or tail the same? Not an expert here so any advice helps. Going to 02 5.3 with dished fp. Can i avoid drilling out the flexplate to match my th400 converter? If i buy a newer tc? Thank s

2. Which vss adapter works best and what needs to be done to pcm for that?

3. Engine mount position keeping the stock trans? 72 2500. Does anyone kno w the exact location on the frame and mount for this setup? Need c20 th400 help. Thanks for the help

Getting ready for machine shop and will share build soon.

[rennat_2006]

Originally Posted by 72GreenMonster

1. Current stock 402 400 trans. What is the stock stall and do i need to upgrade torque converter? If so which converter would i buy or is a matching bolt tc compatible with the older trans or tail the same? Not an expert here so any advice helps. Going to 02 5.3 with dished fp. Can i avoid drilling out the flexplate to match my th400 converter? If i buy a newer tc? Thank s

2. Which vss adapter works best and what needs to be done to pcm for that?

3. Engine mount position keeping the stock trans? 72 2500. Does anyone kno w the exact location on the frame and mount for this setup? Need c20 th400 help. Thanks for the help

Getting ready for machine shop and will share build soon.

I would recomend going to a 2800 or so stall converter, ls engines seem to feel like they lack a little bottom end and going with a little higher stall helps out a bunch

Yes you can get a th400 tc with the ls bolt pattern.

We used one from autometer i believe it was many years back. It was a pass thru style T that connected to the trans then the factory cable attached to it inline and had the electric feed coming out the side. Match up the pulses from the adapter to the stock pulse count or have the computer tuned to match the adapter. Honestly the only thing the ecm needs to see with a non electric controlled trans is 0mph when stopped and anything above 1mph while moving to control the IAC and idle correctly.

[LH Lead-Foot]

I am a little unclear on your project, but can figure out certain things to get your plans going.
#1 The TH400 will bolt on you "LS" engine, there is just no hole at the 2:00 O-Clock position. You will have to use the donor engines trans bolts and make sure you keep the locating dowel pins on both sides.
#2 The front drive shaft slip yoke works fine and is still used in 03 Tahoe.
#3 If the engine is a Vortec or truck engine and this is you "Dished Flex Plate" all you need is a $22 eBay adaptor that fits the nose of the torque convertor and the inside of the engines crankshaft to keep it aligned.
#4 Truck engines have an ugly intake but its design produces low end torque out the wazzoo and if you change the intake, yes, I would think about torque convertor change. The OEM TC, will have about an 1830 RPM stall. If the torque convertor is removed, look for a sticker. You can find internet answer on stall.
#5 Engine mounts are "Dirty Dingo" that everyone except me uses. Your mounts should be clam-shell with front to rear single bolt to bracket. They fit current mount stands and the correct dirty dingo plate allow for back & forth movement to clear headers, frame and tranny. Lot of automatics have to have the ears cut off for certain header applications.
#6 Headers have improved, but check out "Speed Engineering" as they have come out with a new header recently to fit the older "LS" C10 crowd that help get around the tranny.
#7 I have part #'s for VSS parts, but yes, you to do some work. The PCM requires a high resolution signal. Now, you will see a lot of specs on how many signals per mile you need, but it all come down to this.
(1) purchase a 40 tooth VSS wheel that goes onto the output shaft of your TH400. The ACDelco P/N 24202711 reluctor wheel. The old one come off with pushing down clip, tap and slide off back. New one is made of sintered iron and must be gently heated with a torch and have a flat cut end pipe that will go long enough to drive the new one on. It has no clip, just press-fit. Heating makes this easier to install as the can crack easy if not careful.
(2) VSS sensor is a phone call to "Monster Transmission" customer service can help find the right two wire sensor. You can order or get a wire connector from the bone yard. The sensor has two small metal bars that inside have a magnet between them. The wire core is wrapped where it produces an A/C signal get increase in voltage and frequency with speed. These wire go right into the PCM as a schematic will show VSS High, VSS Low. Either works. The wires coming from the VSS should be twisted then a round added. Place two wire into your bench vise, the other end in a drill, twist about 9 times per foot, but could it not critical. The ground simply goes to the frame with a clean spot, star washer and bolted down, then place it on the twisted pair all the way to the PCM. Have it long enough to exit at the PCM's harness, then go to the frame again. Home improvement stores sell metal tape that's 2 1/2" wide & about $8.00. Use electrical tape in a couple of places to hold everything together just a little, then wrap the entire harness with the foil tape the entire length. Start at a sharp angle to wrap sideways to make it easy. This helps keep RF induction or electrical noise out of the VSS signal to the PCM. Route next to the frame on the drivers side. Fabricate a metal "Heat Shield" if near the exhaust and use existing holes to mount as needed.
#8 The flex plate holes to torque convertor to not line up perfect. The OEM torque convertor mounting bosses are in a slightly smaller pattern. This is easy to fix with a "Rat Tail" file to move the hole about 3/16" inward of smaller.
Hope this helps. Retired ASE Master Tech / master tech since 1978

[72GreenMonster]

Originally Posted by LH Lead-Foot

I am a little unclear on your project, but can figure out certain things to get your plans going.
#1 The TH400 will bolt on you "LS" engine, there is just no hole at the 2:00 O-Clock position. You will have to use the donor engines trans bolts and make sure you keep the locating dowel pins on both sides.
#2 The front drive shaft slip yoke works fine and is still used in 03 Tahoe.
#3 If the engine is a Vortec or truck engine and this is you "Dished Flex Plate" all you need is a $22 eBay adaptor that fits the nose of the torque convertor and the inside of the engines crankshaft to keep it aligned.
#4 Truck engines have an ugly intake but its design produces low end torque out the wazzoo and if you change the intake, yes, I would think about torque convertor change. The OEM TC, will have about an 1830 RPM stall. If the torque convertor is removed, look for a sticker. You can find internet answer on stall.
#5 Engine mounts are "Dirty Dingo" that everyone except me uses. Your mounts should be clam-shell with front to rear single bolt to bracket. They fit current mount stands and the correct dirty dingo plate allow for back & forth movement to clear headers, frame and tranny. Lot of automatics have to have the ears cut off for certain header applications.
#6 Headers have improved, but check out "Speed Engineering" as they have come out with a new header recently to fit the older "LS" C10 crowd that help get around the tranny.
#7 I have part #'s for VSS parts, but yes, you to do some work. The PCM requires a high resolution signal. Now, you will see a lot of specs on how many signals per mile you need, but it all come down to this.
(1) purchase a 40 tooth VSS wheel that goes onto the output shaft of your TH400. The ACDelco P/N 24202711 reluctor wheel. The old one come off with pushing down clip, tap and slide off back. New one is made of sintered iron and must be gently heated with a torch and have a flat cut end pipe that will go long enough to drive the new one on. It has no clip, just press-fit. Heating makes this easier to install as the can crack easy if not careful.
(2) VSS sensor is a phone call to "Monster Transmission" customer service can help find the right two wire sensor. You can order or get a wire connector from the bone yard. The sensor has two small metal bars that inside have a magnet between them. The wire core is wrapped where it produces an A/C signal get increase in voltage and frequency with speed. These wire go right into the PCM as a schematic will show VSS High, VSS Low. Either works. The wires coming from the VSS should be twisted then a round added. Place two wire into your bench vise, the other end in a drill, twist about 9 times per foot, but could it not critical. The ground simply goes to the frame with a clean spot, star washer and bolted down, then place it on the twisted pair all the way to the PCM. Have it long enough to exit at the PCM's harness, then go to the frame again. Home improvement stores sell metal tape that's 2 1/2" wide & about $8.00. Use electrical tape in a couple of places to hold everything together just a little, then wrap the entire harness with the foil tape the entire length. Start at a sharp angle to wrap sideways to make it easy. This helps keep RF induction or electrical noise out of the VSS signal to the PCM. Route next to the frame on the drivers side. Fabricate a metal "Heat Shield" if near the exhaust and use existing holes to mount as needed.
#8 The flex plate holes to torque convertor to not line up perfect. The OEM torque convertor mounting bosses are in a slightly smaller pattern. This is easy to fix with a "Rat Tail" file to move the hole about 3/16" inward of smaller.
Hope this helps. Retired ASE Master Tech / master tech since 1978

LH Lead Foot
Thanks so far got the tc adaptor, have the stock th400 tc from my 72 and am going with a summit stage 1 cam and tbss exhaust manis, tried to buy speed engineering headers but living in California was a no ship, so plan b. Will make a little more hp so should i change tc? Rennant recommend s 2800 stall?
Already bought lsx motor mount plates hoping they work with tranny staying where its at. Think it will work?
Many thanks!

[72GreenMonster]

Lead Foot
Also working on the vss, tape so thanks but how long will it take to work the bolt holes with the rat tail?? Just curious?

Drilling?
Thanks

[LH Lead-Foot]

The PCM does like to see a VSS high resolution signal to know it moving. Between MAF, MAP, APP & VSS, it can calculate engine load which change the timing and injector duration...anticipating your wishes.

As for the flex plate, you have probably seen the slightly smaller pattern the TH400 takes and comes real lose to the "Deep Dish" truck holes.
Just mark with a scribe using the round of a small socket to have an idea. Get your rat tail file chucked into your favorite drill. When placed into the hole, go in reverse at low speed to have good control. The other end on the rat tail can be guided real easy with a 4 - 6" piece of gas or water pipe about 1/2" or so. Just put on your welder glove to hold, then push down on the direction you want to go.

Just do all little at a time, about the same amount, then test fit to see your achievements. You'll be shocked how easy it is, plus remove the burr on the backside of the flex plate when done so the bolt will seat good. Works great and will take less than ten minutes to do all three. Save you elbows, use the drill & pipe.
Then, amaze you friends when they happen to come over with something they have never seen before.

[72GreenMonster]

Originally Posted by rennat_2006

I would recomend going to a 2800 or so stall converter, ls engines seem to feel like they lack a little bottom end and going with a little higher stall helps out a bunch

Yes you can get a th400 tc with the ls bolt pattern.

We used one from autometer i believe it was many years back. It was a pass thru style T that connected to the trans then the factory cable attached to it inline and had the electric feed coming out the side. Match up the pulses from the adapter to the stock pulse count or have the computer tuned to match the adapter. Honestly the only thing the ecm needs to see with a non electric controlled trans is 0mph when stopped and anything above 1mph while moving to control the IAC and idle correctly.

Thanks Rennant so ill look for a 2800 stall? Any part numbers which specific tc would i search for? 4l60 or th400? Have dbw so no iac? No vss will not affect this sengine trans setup? Prefer to optimize and not settle at having a few bugs
Thanks again