TH400 INTO F-BODY

[redvictor]

Anyone have a link to a company that supplies the conversion parts? i already have BMR for the driveline/suspension. I need one that does the speedo/wiring harness/flexplate stuff......

[Randy 406]

What year F-body?If it's a newer one try asking on www.ls1tech.com Even if it's a third gen you may find your answer there.

[redvictor]

What year F-body?If it's a newer one try asking on www.ls1tech.com Even if it's a third gen you may find your answer there.
it's a 1994... i posted on LS1 tech and got an answer...thanks.

[DERTY]

The TH400 is a direct fit to a LS1 with the ultrabell. The block lacks a bolt hole on the passenger side at 2 o'clock. Otherwise all of the other holes are there. The speedo sensor is something that can be plugged into the trans. The wiring is simple for a car that was a LS1 with a M6 trans. It's a little more involved for an automatic trans. The trans also reuses a M6 trans crossmember with a spacer for the trans mount. Beyond that, the conversion for me was pretty easy.

What engine and engine management are you going to run? That would be more helpful in figuring out what you need to do. Since the flexplates are not the same between a LT1 and a LSX, etc.

[LTLHOMER]

I have an ls1 in my 94 and I used a stock th400 with ls1 specific converter/flexplate. Stock m6 crossmember with a slot cut in it. Very simple.

[redvictor]

it's an LT1 engine with a 4l60e trans.Engine has a Vortech charger on.Not sure if it has the stock computer or not...i'm pretty sure it has...
Crossmember isn't a problem,BMR have taken care of that.
I thought the TH400 fitted directly to the LT1? and the flexplate was useable with the TH400 converter?
Doh if it doesn't....
harness coversion is probably the thing i'll need the most

[LTLHOMER]

it's an LT1 engine with a 4l60e trans.Engine has a Vortech charger on.Not sure if it has the stock computer or not...i'm pretty sure it has...
Crossmember isn't a problem,BMR have taken care of that.
I thought the TH400 fitted directly to the LT1? and the flexplate was useable with the TH400 converter?
Doh if it doesn't....
harness coversion is probably the thing i'll need the most
th400 does fit directly to lt1...not sure on flexplate but it sounds right...I have a LS1 in my 94 LT1 body style car which was why I said the flex was different for me...I assumed you were swapping an ls1 cuz it's the ls1 section but I assumed wrong...lol

[DERTY]

Not technically an LS1 section. However, the bellhousing should fit fine. The flexplate should fit fine to a converter. The largest issue might be the converter pilot length. However, I think that the LT1 itself is a standard SBC size as opposed to the LS1 which is 1/4" longer. Most Converter companies will know the dimensions if you simply tell them LT1, TH400 and midplate thickness (if you have one).

For the Powerglide and the TH350/400 there are no provisions for a speedometer normally. The TH400 can often times be purchased with the GM VSS Sensor installed. All that you would have to do is splice in the connector to the factory harness. The VSS Sensor is GM part 8655291 and it requires the reluctor ring GM part number 8655315. The pigtail harness is GM part number 12085498. All are available from the dealership, but may have to be ordered. You can either order them from GMPartsDirect.com and pay their high shipping charges or order it from the dealership. Expect the parts to cost close to $200. Once you have the speedo spliced in you will need to calibrate your PCM. For cars converting from an M6 you have to multiply the tire diameter by 2.5 to make up for the different number of pulses per mile that the PCM will see. A4 cars should be ok. Ideally you can calibrate it in third gear under load by taking your RPM and MPH (or by eye) and then running it through a gear calculator to find out where you are. Or ask your local law enforcement for some help! Ideally the radar speed checks are a nice way to confirm it as well.

A Lokar cut to length dipstick is the way to go for that part. As far as other bits and pieces, I'm not sure what other info you need. This should be a good start.

These should help.

http://www.derty.org/ls1tech_trans_faq.htm
http://www.derty.org/photogallery/data/media/20/th400.htm
http://www.ls1tech.com/forums/forumdisplay.php?f=13

[redvictor]

thanks for the info....incredibly helpful to me....... car is due in a month or so....i'll be asking questions..lol