OK, its a go. Derty already has a writeup started , but lets all get together and post questions that you would like to see addressed in the FAQ. By no means am I a TH400 expert, but I have been extensively researching it before dropping the cash so I will have a few resources to add. I know this is going to take time and effort from everyone, but its all about having fun – right?

This post will be for questions, concerns, issues, specs, etc that you would like to see addressed in the FAQ. Don’t clutter it up. If you see a question in this post that you can answer, then by all means share your experience. In the end we will compile it up and sticky our TH400 faq. Even if you want to email me little tidbits of info, or write ups you have I will personally volunteer to write the FAQ and then submit it to a mod/expert for their OK. PM me for my email addy if you can answer any of the questions in this post. (mods have enough to do so I don’t want to bombard them with this “project”) Lets focus on the 4L60e to TH400 swap for now, then we can work on the M6 to TH400 swaps.

(mods – do you want to make this post a sticky?)

Here are a few to get it going:
1. General overview of the benefits and disadvantages of the TH400 swap. What’s the TH400 all about?
2. Modifications that will need to be made to your interior (shifters)
3. Common upgrades, why you would need them, benefits and disadvantages of the upgrades (ie, gearing, flexplate, scattershield, ultra bell, transbrake)
4. Address the “no overdrive” fears, what it takes to install the Gear Vendors OD unit
5. Converters (NA, poweradders)
6. Maintenance
7. Driving a TH400, how it behaves, etc

 

My questions pertain to both the TH400 and the TH350.

For the speedo:
Is the VSS Sensor GM#8655291 and the Relutor ring GM#8655315 compatible with all TH350/TH400 tailhousings? or is there certain tails that which they won't fit in?

Is a different pilot bearing necessary for the swap?

Gear Ratio's in the Tranny, and if the same ratio's apply to all years.

What stock drivelines will work with what size tail?

Will the 6.0L flexplate work with the TH350/400 converter? Any year specific?

Answers:

TH350/400 uses a small pattern TQConvert with an LS1 pilot.

TH350/400 Converter can use a '98 flexplate.

Manual Valvebodies do not require the vacuum modulator.

Correct me if I am wrong on anything.

 

Feel free to contribute to this. I already have a lengthy writeup with plenty of pictures. Unfortunately when I moved my website around I had not had a chance to move most of my writeups. But, I'll get cracking on it this weekend and get it posted. Let me know what questions you have as well and I'll try and address those more specifically in the FAQ as well.

 

Can you use your stock A4 shifter with TH350/400? Yes, as long as it's forward valve body.
Can you use a stock A4 crossmember in the swap? Yes, the mount perch has to be moved back 2-3".
Will cruise control still work after the swap? Yes
Can you drive the car after the swap, even though you haven't have the tranny items in the PCM turned off yet? Yes
How many bellhousing bolts do you NOT use in the swap? 2

 

Not sure on a TH350, but this works on a TH400.
The stock A4 shifter can be retained ONLY if you have a forward valve body in the transmission.
The mount tabs on the transmission end of the shift cable can still be used but you must drill a hole in the center of the other 2 holes and use that hole to mount it to one bolt on the tranny pan. It lines up perfect.
Inside the car, no changes need to be made. When you shift to 1st on the tranny, your shifter will only come down to the 2nd gear position on the shifter, so don't try to pull it back farther. Park, reverse, neutral all match up fine.

 

the th400 does not take any more power to run unless you try to do it quickly. time is the problem, if you do it quickly, it's big and strong, it can take tons of power. light parts really show up with a motor low on torque and high on hp. example if you spend 3 seconds in low and it takes 3 hp to run the trans. cut the time in half, 1.5 seconds in first it can take 9hp. if you don't have much time think light. lf your car is your daily driver and a week end racer and you want a 400, run 3.23's a 10" converter stock tranny ratios. do not buy a tc by price only. ask for a toyota 10" core to begin with. A-1 automatics canoga park is the place.

 

I installed a th350 in my car and i am useing the stock shifter and it is working perfect. It is a reverse valvebody. Did not do anything to shifter. You shift first to 2nd and then you push button in and shift to third.

 

If you want to run a "standard" TH400 converter, and the TCI flexplate, the TCI spacer can be replaced with one with a longer nose. This is because a standard converter doesn't have a pilot long enough to engage the back of the crank. Here are some pics of the spacer I made:

 

Here's some info Steve:

https://ls1tech.com/forums/showthrea...actory+shifter

 

Here is what I learned from my 4L60E --> TH400 w/Transbrake:

• I used the BMR TH400 crossmember, it fit perfectly.
• I also used the BMR X-treme torque arm, it comes with a driveshaft loop so don't purchase one seperately.
• You use only five (5) bolt to secure the trans to the engine, left three and right two. The middle top bolt is not used, not are the bottom two. Only the one next to the alignment pins and the upper left one.
• A 1998 flexplate can be used with an SBC converter, you'll need 1/8" space or washers.
• You will need (if you use an SBC converter) at least a 7/8 pilot spacer (B&M p/n: 2801054-19, not sure if we sell it individually)
• Do not use Lokar Firewall mount dipstick (p/n: TD-3350400FM), it is too short and will end up under the cowl, hard to reach for filling up the trans/checking fluid level. It can be done though.
• Use the speedometer items from a 3L80 (3 speed trans) truck, part numbers were previously posted (GM# 8655291, 8655315), they work perfectly on ex-A4 cars. Just cut the (will verify wire colors) wires and splice them to the connector (p/n: 12085498)
• You will need 1/2" NPT hose pipe adapters to fit into the trans (may be different, 5/16" NPT) with 5/16" hose to mate up to your OEM cooler lines. Just use a pipe cutter, about 3" of 5/16" hose and four hose clamps and it will seal up fine.
• I used my HPTuners software to delete all the references to the A4 trans and it has worked great, you can also use a manual trans program or ECM, but the speedo signal will need to be multiplied by 2.5 to read correctly.
• If you use the OEM park/neutral safety wires (connect together purple and dark green) and the reverse wires (connect together brown and light green), the computer will know the trans is in a drive gear.
• My driveshaft was made by Wenco Industries and the length was exactly 44" using a KTRE 12-bolt with 1350 yokes, spicer u-joints.
• My shifter of choice was a B&M Quicksilver for positive gear selections, it works better than OEM.
• I will be adding a B&M Trans cooler with integral fan to keep the trans fluid cool.

 

I used a convertor built by ATI for a 98 LS1 flexplate and I used no used spacers or pilot spacers.
Use the Madman dipstick filler tube and dipstick. Fits like Stock.
You can use the stock tube adapters from your 4l60e for the lines. They screw right into the TH400.
I didn't have to change ANY wires up for my neutral/reverse/drive. I have a forward valve body though.

 

I have my current writeup available. I just realized that I had made the photo gallery, but I never posted the link. Here's all the photos: http://www.derty.org/photogallery/ca....php?cat_id=20

Here's the writeup (the link is at the top of the photo gallery too). http://www.derty.org/photogallery/da...a/20/th400.htm

The new format will be more inclusive then this one and will have a lot of questions answered. I've just been swamped trying to get a lot of stuff done.

 

Just got off the phone with Lokar. This is the correct part# for the dipstick that will be long enough to use. PART# TD3350-400-FM-36. The only difference in the part numbers are the last 2-digits (36) which represent a 36" long dipstick.

 

Does anyone know of a Yank dealer that might have the TH350 crossmember with torque arm bracket that Yank has on their website? I called several times at Yank and noone answers. I left messages and no response.

I settled for the Spohn Torque arm #402. Front of the TQ arm mounts to the body, its adjustable and also works with true duals. It runs about 425 w/shipping.

 

If im not mistaken I beleive you can use your stock Aluminum drive shaft if you have an th350/th400 with an 9" tail shaft.

 

A TH350 9" tail is 30 5/8" and a T56 is 31.90" these two are close and I'll let you know next week if they are close enough. Now a TH400 9" tail is 34" long and the short tail is 28 1/4" long, and also it uses a different spline than the TH350 and T56. A different yoke and different driveshaft length will be needed if swapping the T56 to TH400.

 

I just got back from Japan last week. So I'm finally starting to get readjusted. Here is the first write up I did. It's mostly TH400 stuff. http://www.derty.org/photogallery/da...a/20/th400.htm

I already have started to put most of the info from the questions into a new format. You can get a look at the first upload of it here. http://www.derty.org/ls1tech_trans_faq.htm

I have a lot more to go, that's for sure. The amount of information we've gathered is overwhelming. I'm just trying to find a way to organize it all so that it makes sense. If you guys have pictures of any of your installs, that would be cool too. I have plenty of TH400 stuff. Any other setups would be cool to have. Just send them to me to transfaq@derty.org.

 

Here is a few updates after my install.

If you order a new flywheel from GM and you say you need a '98 flexplate (GM#12580709)(also the exact same flywheel as a 6.0 liter) you will get the wrong one. This problem can be fixed by filing the holes about a 1/16th to an 1/8th to match the SBC bolt pattern. This will not hurt anything.

Flywheel

If you use a 9" tail TH350 the driveline will work. It is in the tail about 1/2" to 3/4" less than the T56.

9" tail

The 9" tail TH350 WILL NOT WORK with the stock T56 crossmember unless you have a specific tail that the transmission mount actually bolts to the tail. I modified the stock crossmember using a piece of flat steel plate to make it work. I also used the stock T56 rubber mount to bolt to the crossmember. Its easier to build the crossmember when using the stud type stock tranny mount that the T56 uses.

Modified crossmember 1
Modified crossmember 2
Modified crossmember 3
Modified crossmember 4
Modified crossmember 5

If you have True Duals. Crawl under the car and look where the Spohn TQ arm mounts! My #402 Spohn TQ arm did NOT work with true duals. I had to have them re-done.

Spohn Tq arm mount
Crossmember holes

A few others:
Lokar Dipstick
TH350 w/9" tail

***Pics updated 3/29/2008***

 

you can edit your PCM to remove all of the codes or you can flash your PCM with an M6 flash (this is what Speed Inc said they would be doing for my TH400)

 

You said the 98 and 6.0L flexplates are the same, but your P/N for the 98 is 12580709 and the 6.0L is 12551367, did one just supercede the other or are they 2 different flexplates?