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In this article I will try to document step by step on how to make an adaptor plate for the Chevy (GM) TH400 transmission. You can read all about the history of this transmission somewhere else, but in this article we will open up and dissect this bullet proof transmission into our V8 engines. The tranny is massive and will cost you about 44 hp to operate this tough tranny. The reason I pick this transmission is because its very tough. This fully build tranny can handle at around 2000 hp. Secondly, this transmission is cheap. Matter of fact its dirt cheap. Nicely build is about $800 and capable of handling about 800-1000 hp. I paid $125 for the transmission. A complete rebuild master kit is about $85 – $180 and a complete performance shift kit is about $60. With labor about $300. I can get a very nice strong transmission for about $600.
Enough said about this best bang for the buck transmission. Lets talk about parts you will need.
1. TH400 Transmission: (ebay or local recycler or junk yard for about ($85-150) or get a prepare build.
2. Torque converter: It has to be custom made. I have worked out a UZFE/TH400 hybrid TC. I called this LEVY400 (Lexus-Chevy 400) Please contact me for details
3. Adaptor plate
Adaptor Plate: From what I hear via the Chevy camp. This adaptor plate also work with the following GM transmissions:
* 200-4R (Over drive article)
* 4L60E (Need confirmation)
* 4L65E (Need confirmation)
* 4L85E (Need confirmation)
* TKO (need GM version bell housing) 5 speed
* T5 (need GM version bell housing) 5 speed
* T56 (need GM version bell housing) 6 speed (Swapping 6 speed article)
|Custom Torque Converter||$500|
|HP Master Rebuild Kit||$180|
|Performance Shift Kit||$60|
|Rebuild Labor Cost||$300|
|Transmission Mount||$8 Need slight modification|
|3/8″ steel plate||$25|
|Labor for Adaptor plate||$125|
|Bolts & Washers||$11|
|Total||$1,401.99 so far|
|Potential Cost||Custom driveshaft ($200-$350) Optional|
|Installation of transmission $300|
I would say for about $2,000 you can get the complete conversion. $2,000 is lot of money, but still very cheap comparing for other transmission upgrade. This transmission can potentially handle 1,500 hp. However, with $2,000 you don’t have much choice on Lexus upgrade transmission. So even its a lot of money but its still the best bang for the buck.
Torque Converter (LEVY400):
The TH400 was not made for the Lexus-Toyota UZFE engine. However, with passion, it you can make it work. The TH400 transmission mating surface is larger then the UZFE mating surface. The TH400 can literally cover over the UZFE engine.
Here are some pictures of the LEVY400:
The blue torque converter (left) is the modified UZFE/TH400 and the right is the stock Lexus V8 TC. Notice the height difference and the hub or neck size? The LEVY400 is massive. This LEVY400 requires lots of internal machining. Please contact me for more detail on this hybrid torque converter.
The picture below is the LEVY400 installed into the TH400. This TC is a perfect in both TH400 transmission and the UZFE flexplate. The second picture is the LEVY400 mounted on the Lexus 1UZFE Flexplate and once again, its a perfect fit.
Here are few more pictures of the LEVY400 mating with the stock flexplate.
The LEVY400 TC fit perfectly between the engine/transmission. Here are some pictures of the TH400 transmission actually mock fitted the UZFE engine. The engine/transmission mate without the adaptor plate.
While I was hunting for a mild steel plate. The net wanted almost $90 plus shipping for a 3/8″ x 17″ x 17″. I went to a local metal yard and got the measurements I wanted for $25. I was very happy and you can’t beat that deal. The plate is on the left and the stock oem Lexus A341E is on the right. I place the bell housing all the way near the edge of the plate so this will save me some cutting.
Toyota/GM Adaptor Plate:
I drilled two 14 mm holes on each side of the bell housing and bolt two 14 mm to stabilize the oem bell housing to the steel plate. Please see picture below
After the bell housing is securely bolt onto the steel plate, then I used a Sharpe and tracing around the outside as well as inside of the oem bell housing. The most important would be the inside line. This is where the important cuts occur. The initial cut will be the inside of the bell housing. I will continue to drill all holes and start cutting the inter portion very soon.
After spending $65 on the inner hole and all other bolt holes. This adaptor is partially done. Its partially done is because I need to mount the adaptor to the engine with the LEVY400 in order for me to align the transmission. Oh by the way, this method will work. You need the laser guided BS tools to do this. Some seller will brag about his laser guided adaptor plate. Its full of it. He used it because he has no TC or clutch to guide the transmission. Anyway, As you can see the pictures below. Its turning out quite nice. The picture on the left was taken at a local welding shop and plasma cutter is just to sick. The picture on the right is the plate is mounted on the engine.
Once the plate is mounted on the engine, then we can insert the transmission. I also used a jack on the transmission to make sure the mounting surface is flat to the plate with the transmission. The torque converter align the input shaft up & down and side to side. The plate is the guide to align the tilting component.
Once the transmission is installed, then u need to level the transmission side to side in relationship with the engine. I made two apex mark on the transmission and the engine. So the engine/transmission is align in relationship with each other. I also use pliers to hold the plate/transmission together while I used a Sharpe to trace the outline of the TH400 mounting surface. Once the transmission and the plate is secure and I used a 3/8″ drill bit and drill slightly to the plate to make a mark on those mounting holes. The reason I did that was because the Sharpe was too big to make any mark for drilling.
After making the marks with my drill bit, the plate looks like the pictures below. Now I can take plate back to the welding shop and they will cut the plate again to the contour of the TH400 mounting area. At the same time, the shop will drill the mounting holes too.
Ok, after spending an additional $60 dollars, I got the plate cut up according to the TH400 pattern and drill hose according to the mating surface. I also bolt the adaptor plate to the block and everything fit perfectly.
Here are some pictures with the TH400 attached into the block via the adaptor plate. As you can see the transmission and block are mate perfectly alignment.
Here are closer pictures of the LEVY400. Its not as nice as CNC, but this will do the job. Function is more important than fashion.
Here are more pictures of the LEVY400. Over all, I am extremely or you can say it I am lextremely happy with the result. However, I am sure a Japanese Anime Character will copy my work and produce it himself and make lots of money with it.
Since the adaptor plate is mild steel and I didn’t want it to rust, so I spray paint it silver to product this plate from rusting. I also welded the bolts to the plate so its much easier for installation.
What is next? Yoke modification is what I will be doing. I will modify the TH400 yoke and the Lexus yoke to mate with each other. This is also an interesting task too.
The Chevy TH400 truck yoke is more beefier then the standard passenger car yoke. The are two version of the tail length. Short and long of course. The short tail is what you want. The shorter version will be much easier to work with. Here is a picture of the standard TH400 truck yoke (left) and the A340E yoke (right). The pictures below are side by side.
The pictures below are yokes side by side. The comparison of the two yokes. Left is the TH400 and the right is the Lexus SC400 (A341E)
With some digging and asking around. I found a local machine shop would cut part of the TH400 yoke and mate it with the A341E yoke for about $70. They will also going to balance the finished yoke too. This is how it would look like once its done. I used a basic photo program to cut and paste the two yokes together. The front would insert right into the TH400 shaft and the rear would mate with the Lexus stock driveshaft. This procedure sounds easier then it looks. Since the TH400 transmission is completely different from the Lexus. There is 3″ difference so shorten the driveshaft is a must.
Transmission Mount: Coming Soon!
Driveshaft Mods.: Coming Soon!
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