TH350/TH400 Frequently Asked Questions
 

trying to sum stuff up here- PM me the info you want added, I dont want this thread turning into the last one that is 10 pages of questions and comments
If you have a question you want answered make a thread and pm me the thread and I will add the answer into this.


Will cruise control still work after the swap? Yes

How many bellhousing bolts do you NOT use in the swap? 2


Converter-
Can I use a standard th400 converter? Yes but certain conditions exist..The converters typically used are standard SBC converters that have two minor modifications. The first is that they use a LS1 Pilot diameter. The second is that they should have the pilot extended 3/8" to make up for the difference in length between the LS1 and a traditional SBC. 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.

With the use of a stock flexplate and standard converter, you will need some special spacers.

I highly recommend to just buy a TC from a company such as Yank, Fuddle, Vig., etc.. and tell them you are putting a Th400 in your car. The TC will then come with the proper pilot and bolt pattern. The use of spacers is to much of a hassle in my eyes.

Flexplate-

The stock flexplate can be used. Some modification to the bolt hole may be required. I did not have any problem with mine. I had a special made TC for a th400 to ls1 and it bolts right up without spacers or modification.

If upgrading the flexplate, use the TCI number of 399753


Derty Guide
There are several important safety factors that need to be considered if your transmission swap is being done for use with drag racing. Ideally these things should also be considered for even vehicles with factory transmissions in accordance with either IHRA or NHRA rules and guidelines. It is recommended that you use a SFI certified flexplate with your new transmission. There are numerous advantages to doing this. The first is that the SFI approved flexplates are more durable and less prone to breaking like the factory flexplates. Companies like TCI and Reactor make LS1 flexplates that are certified already. TCI Sells theirs as a small bolt pattern 168 tooth flexplate, part number 399753. Common failure modes with the factory flexplates is that they often break or crack where the convert bolts up to it. Also, if you are going to use the stock flexplate it is not recommended to use the ARP flywheel bolts. The unthreaded shoulders on the bolts are longer then the thickness of the flexplate, which will not allow you to tighten it properly. If you are using aftermarket flexplate, the use of the ARP bolts is highly recommended. Here you can see the difference between the bolts.

http://www.derty.org/photogallery/da...0/DSC01310.JPG


Flexplate Scattershield

Derty Guide
The NHRA and IHRA require cars to be equipped with a flexplate scatter shield and a transmission shield. There are several ways to accomodate this requirement. The first is that CSI produces a composite shield that covers the entire bellhousing and the transmission as one piece. The second is that you may use a SFI approved bellhousing/scattershield like a Ultra Bell. You may find that space constraints a little tight to use the CSI shield, but it is possible. Most aftermarket transmissions can be modified to allow the use of a JW Ultra Bell. Unlike a stock bellhousing on the transmissions, the Ultra Bell is rated as a SFI approved scatter shield. The Ultra Bell does require two minor modifications to fit the LSx blocks. The first is that the ears that come on the ultrabell for other block applications may be cut off. The second is that the bellhousing face that mates to the block is considerably thicker then the stock bellhousing. This ultimately makes the bellhousing interfere with four bolts located on there rear cover of the engine. This can cause some significant misalignment problems and ultimately damage the transmission and/or converter. Here you can see the rear cover and the four upper bolts, followed by the modifications required in the bellhousing.

http://www.derty.org/photogallery/da...0/DSC01309.JPG
http://www.derty.org/photogallery/da...0/DSC01330.JPG

Five bolts are used to mount the bellhousing to the block. The four holes adjacent to the locating pins and the next upper left hole by the driver side cylinder head. The top center hole in the block will not be used and the block also has no provision for the upper right hole in the bellhousing. The lower two holes in the oil pan that the factory bellhousing bolted to are not used as well.


Transmission Shield
Derty Guide
Finally you need to consider a transmission shield over the drum area. TCI Makes a aluminum SFI approved shield for this purpose. It's a simple bolt on shroud that covers the drum area. One of the most dangerous failures in a transmission, besides a flexplate failure is the drum letting loose. Many racers each year suffer a severe transmission failure like this that ultimately rips through the floorpan of the car when unchecked. A secondary result of this is that hot transmission oil is scattered everywhere. Of the racers that have experienced this they now often run an Ultra Bell, a transmission shield and a transmission blanket. The thinking behind the use of the blanket is to contain any remaining parts that ricochet off the shields as well as the oil. This is purely an optional step, but it is completely dependent on how safe and protected you want to be in the event of a serious failure.


Crossmember-
Can you use a stock A4 crossmember in the swap? Yes, the mount perch has to be moved back 2-3". This is done by modifications with a welder.

Th400 with 4in tail will bolt right on to the T-56 crossmember. Use some washers or a 1X1 piece of square tube as a shim to raise the tail to the proper level.
The T-56 x-member will work with most applications with some modification.

There are some places that sell a swap crossmember, such as YANK and BMR. Available with or without the torque arm mount.

Torque Arm-
The th400 will not have provisions for a TA. You have 2 options.
1. Stock mounted TA
2. Chassis mounted TA

Spohn, Madman, BMR, UMI, etc.

Mount-
Do not use a solid tranny mount. It will crack the case or the bellhousing the first time you leave hard.
Use a GM mount or an energy suspension mount # 3.1108(G/R)
Dont skip out on replacing the mount, it is cheap and pays off.


Stock Shifter-
Can you use your stock A4 shifter with TH350/400? Yes, The stock A4 shifter can be retained 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.

Threads retaing to this- https://ls1tech.com/forums/showthrea...actory+shifter


Aftermarket shifter-
You can use just about any aftermarket shifter you want. No one makes a direct drop-in shifter though. All will require some modification to install.

https://ls1tech.com/forums/automatic-transmission/580107-my-turbo-action-cheetah-shifter-pics.html

Examples-



Wiring
You can wire in your factory shifter wiring to your aftermarket shifter if it comes with options to do so. If not you will need to do the following-

A4 cars, connect these wires together that come out of the old shifter harness. It is a 6 wire connector going into the factory shifter.

orange w/ black stripe + black wire = hatch release to work.

Finally the brown and light green wires should NOT be wired directly together. Doing so will cause your reverse lights to stay on at all times. You can run them threw a momentary switch or just leave them apart like i did.

M6 cars-
For M6 cars you splice into the lower clutch sensor wires. There is a plug that goes into the sensor at the bottom of the clutch pedal.
The wires are black with a white wire. You can simply splice into those two wires and run them to your new Park / Neutral switch on your shifter. Or just wire them together.

more coming

Case Lengths-

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1 Aluminum Powerglide 14 bolts
2 TH200 Metric 11 bolts
3 TH350 13 bolts
4 TH400 13 bolts
5 TH200-4R 16 bolts
6 TH700-R4, 4L60, 4L60E 16 bolts
7 4L80E 17 bolts



Case Modifications-
The 2 "ears" on the case will need to be cut off with the weapon of your choice. Doing so will allow A LOT easier installation. Be sure to not get any metal shavings inside the tranny.

The stock bellhousing is not removable. It can be cut off and replaced with an aftermarket one for safety standards though. You can put an J.W. Performance Ultra-Bell Bellhousing on your TH400. The original bellhousing gets machined off to install this one. It's SFI approved and yes, it is much stronger than stock

Attachment 623449

Weight-
4l80e- wet 255
4l60e- wet 175
TH400- wet 140
TH350- wet 130
Powerglide- wet 110

gear vendors overdrive- 40


Cooler lines-

TH350, TH250
Fitting Location Thread Size Flow Direction
Upper 1/8" Pipe Return/in
Lower 1/8" Pipe Cooler feed/out

TH400
Fitting Location Thread Size Flow Direction
Upper ¼" Pipe Return/in
Lower ¼" Pipe Cooler feed/out

4L60/4L60E/4L65E
Fitting Location Thread Size Flow Direction
Upper ¼" Pipe Return/in
Lower ¼" Pipe Cooler feed/out

Stock lines will not bolt up to a th400. The use of fittings will be needed. Lots of different ways to do this. I put a barbed fitting at each location in the tranny and then connected a hose to it. Then the other end connected to the stock lines that I cut.
The use of an extra tranny cooler is recommended.

Governor / Vacuum modulator-
If you are not using a full manuel valve body then you will need to hook up your VM. Doing so is done by hooking it to a vacuum source.

If you are using a FMVB, the use of the VM is not needed.


Driveshaft-
In most cases the stock driveshaft will need modified. You can buy an aftermarket DS from many vendors online. Or just take you stock one to a local DS shop with the measurments and they will cut it for you. Driveshaft lengths will vary from car to car depending on a couple factors. If the car is using a 12 bolt or a 9" you will see some variances. Also, if you are using different types of motor mounts compared to others (stock, solid, poly or motorplate). It is best to measure the driveshaft for your application.

TH350 with a 9'' tailshaft will work with the stock DS

see Dennys drive shaft for info on measuring

Yoke-
-4l60e has 27 spline
-TH350 has 27 spline
-TH400 has both options, 27(long) and 32(short)
-T56 has 27 spline

PCM-

Can you drive the car after the swap, even though you haven't had the tranny items in the PCM turned off yet? Yes, you will just have an SES light on that retains to all the A4 codes

I have a 6-speed tune in my car, is this ok with the th400? Yes, infact that is what most people flash the PCM to after a th400 swap


External Links that might help-
Derty's guide
http://www.derty.org/photogallery/ca....php?cat_id=20
http://www.derty.org/ls1tech_trans_faq.htm

Transmission Dimensions- http://www.tciauto.com/Products/TechInfo/trans_dims.asp

What did a th400/th350 come in-
http://www.drivetrain.com/autotranscrossref.html

Acronyms-
4L60E - actual part name for the Automatic 4-speed transmission
4L65E - medium duty 4-speed automatic transmission found in some trucks
4L80E - heavy duty 4-speed automatic transmission found in some trucks
700R4 - older generation 4-speed GM automatic transmission
A3 - 3-speed automatic transmission
A4 - 4-speed automatic transmission
ATF - Automatic Transmission Fluid
DS - Drive Shaft
FLP - Finish Line Performance (Vendor)
TC - Torque Converter
TFP - Transmission Fluid Pressure (switch/valve)
TH350 - Turbo Hydromatic 3-speed automatic transmission
TH400 - Heavy Duty Turbo Hydromatic 3-speed automatic transmission
VSS - Vehicle Speed Sensor

Dipstick-
Derty Guide
Depending on the transmission you can get either a Lokar flexible dipstick or order a hard tube dipstick from Madman. The hard tube dipstick fits nicely but can be difficult to install as you have to do it as you are putting the transmission in. The Lokar dipstick is significantly easier to install. You can custom order a Lokar in longer lengths to increase your mounting options as well. Lokar part number TD3350-400-FM-36 is a 36" dipstick for a TH400 that is optimal for use with an LS1. You can also order them for TH350's and Powerglides as well. The dipsticks are different per transmission as the pan has a different size hole that the dipstick tube plugs into.

I recommend 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.

Tips on removing stock M6 pedals-

Speed-O-
see these threads
https://ls1tech.com/forums/automatic-transmission/277182-make-your-th350-speedo-work.html
https://ls1tech.com/forums/automatic-transmission/479729-free-way-get-speedo-work-th350-th400.html


How to turn off the ABS light and BRAKE light when you use the TH350/TH400 speedo mod.

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Pictures of a th400 install. Thanks to dnkynrbk

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cable wrap around the tranny
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shifter bracket
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Attachment 623411

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I will keep going over this and add more. PM me the info you want added, I dont want this thread turning into the last one that is 10 pages of questions and comments
If you have a question you want answered make a thread and pm me the thread and I will add the answer into this

TH350 lines are 1/4" NPT not 1/8"

TH350, TH250
Fitting Location Thread Size Flow Direction
Upper 1/8" Pipe Return/in
Lower 1/8" Pipe Cooler feed/out

I did TH400 swap and now my shift light no longer is working, is there some reason this would be affected by the swap? Im using a raptor light, and it worked fine before the swap.

1999 long crank LQ4 with TH400

what flex plate do i use ? the non curved one ? hardware ? will my stock LS1 starter work ? what torque converter ? this info is extremely hard to find !!!!!

X2

I will probably end up having a custon one made if I dont find out shortly:gruffy:

flat 6.0L flexplate without the spacer.

I know be it still needs redrilled for the 10.75 converter spacing and isn't SFI approved

Thanks for all the great info

4L80 converters/flexplates use the old school th400 converter pattern.

What connecftor is this?

I am trying to jump these lights out now on my setup.

Thanks

Engine: LQ4 with Callies 4" crank
Flexplate: TCI 399753
Transmission: TH-400
Torque Converter: SBC style 10" from PTC

Here is a picture to show the gap between my torque converter snout and the back of the crankshaft. I measured the gap at roughly .050". Looks like I'll be ordering a GM spacer & bolts tomorrow. This picture shows the gap between the converter and the crankshaft directly in the center of the picture:
Attachment 617816

This is a great thread! However, I have some questions that I didn't see answered.

Which TH400 is the best builder to start with?

I have read that you should stay away from the long tail shaft TH400's. What about a year? Are earlier one better or are later ones better? Does it matter if you are having the transmission built anyways?

What do you do for the vacuum modulator on a boosted application?

X2 ^^ I'm wondering if the year of the TH400's

Did you mean .500"

Maybe I overlooked it but I didnt see any comments on the Vehicle Speed Sensor VSS. Any answers for this in the FAQ?

Joe

Speed-O-
see these threads
https://ls1tech.com/forums/showthread.php?t=277182
https://ls1tech.com/forums/showthread.php?t=479729

x3. The link that was given for the drivetrain.com site just takes you to their homepage. Excellent thread though, this is very very helpful.