Gm Transmission Kit Oh ya!!

[oneandgone]

Well some of you may remember that I'm working on a trans kit to install the GM TH-350 and TH-400 transmissions into the MKIII Supra. If you didn't know about it before, well...you will now!

What we've made uses an adapter plate to bolt the stock Toyota automatic bellhousing to the pump of the GM trans. The stock bellhousing must be cut off of the GM trans as it is one large cast case. This is a very common procedure as racers upgrade to stronger bellhousing all the time.

We also had to design a custom torque converter for this kit. This was the hard part. It's a pretty tight fit, but we got it done. I finally the first one in on Thursday.

I mocked everything up today, and will be ordering the first custom driveshaft in a couple days. I'll be testing this set-up for a while before I put the parts into full production and before I set final pricing. I want to make sure there are no issues once the kits are being sold.

Here's a run-down of what you will need to provide yourself...

GM TH-350 or TH-400 transmission
Stock 7M auto fexplate
Stock shim between flexplate and crank (this is a must have item!!)
Stock 7M turbo auto bellhousing (not sure if n/a and turbo are the same or not)
Stock engine to trans braces (the L-shaped ones)
Stock lower dust cover
Shifter of your choice (I could never please everyone)
Cooler and lines

Here's what will be included in the kit...

Bellhousing to transmission adapter plate (Made of aluminum and fully machined on a 3-axis computer controlled mill, also anodized to prevent corrosion.)
Custom trans x-member
Custom speedometer cable
Custom aluminum 1-peice driveshaft
Custom trans dipstick and tube

I always forget something, so when I realize what it was I'll edit it in later! lol!

Now, on to the pics!!!

 

[oneandgone]

I just want to make sure everyone knows what spacer I'm referring to. It's only used on auto cars, stock manual ones don't use one.

More pics...

 

[drjonez]

lookin good man.....any thoughts on gearing?

 

[IJ.]

Grant: Beautiful!

Can't wait to hear some drive impressions of it!

 

[oneandgone]

lookin good man.....any thoughts on gearing?

Thanks Adam! Are you referring to rear end gearing or different ratios in the trans itself? There are optional gear ratios for the trans, but they're fairly pricey. For the rear, which is what I assume you're speaking of I think my 3:73 is going to work out well, at the strip and on the street. It is going to be a bit wound up at highway speeds, but I don't think it will be unbearable. I would still like to add a Gear Vendors unit at some point, but it will be a while.

Grant: Beautiful!

Can't wait to hear some drive impressions of it!

Thanks Ian! As you're into fabrication yourself I thought you would like this. I've been keeping an eye on what you're doing too :icon_wink and have to say I'm mighty inpressed! :bigthumb:

I'm as anxious to drive it as you are to hear what I think! I imagine it's going to be a bit of a learning curve, what with the manual valve body and all.

 

[IJ.]

Grant: I'm kind of sorry I didn't use the CNC to make my adaptor but as there didn't seem to be any interest in a 5 speed Tremec adaptor, I just did it all manually so it's pretty plain compared to yours!

That's the beauty of the CNC Complex shapes are easy and repeatable now you have the code!

Full manual takes a bit of getting used to !

Ever looked into a Clutch Auto for racing? (poor man's Lenco)

Those Gear Vendors UD/OD units would be the shit going by their vid I looked at! (Gear range is the only thing that stopped me going Auto)

You've done real well on the kit when you get a chance can you PM me some rough costs? (just interested professional curiosity)

 

[dbsupra90]

awesome work!
ive been waiting for good news
glad that converter worked out. any ideas about stall option?

hope the proto goes well. id def like to look into this later this year.

dave

 

[Jester1318]

Were you ever able to find out if this would work with a 700r4 or not?

 

[outofstep]

Second on the 700r4. The 3/400s are much stouter units, but even a 700 will take more abuse than my T04 can dish out.

 

[malloynx]

wow looking good jon. any specs on the converter. what's the stall? what's the STR?

internals kevlar?

 

[drjonez]

Thanks Adam! Are you referring to rear end gearing or different ratios in the trans itself? There are optional gear ratios for the trans, but they're fairly pricey. For the rear, which is what I assume you're speaking of I think my 3:73 is going to work out well, at the strip and on the street. It is going to be a bit wound up at highway speeds, but I don't think it will be unbearable. I would still like to add a Gear Vendors unit at some point, but it will be a while...

yup, i'm more referring to the lack of OD.....

 

[chevyeater]

Awesome news Grant. I guess I'll go ahead and start overhauling/upgrading that TH350 I've had laying around forever.

My tow vehicle has a nice overdrive in it.

 

[suprarcr89]

good to see it come together grant. I know youve been waiting on it.. looks great.

 

[oneandgone]

Awesome news Grant. I guess I'll go ahead and start overhauling/upgrading that TH350 I've had laying around forever.

My tow vehicle has a nice overdrive in it.

^^^^That's what I'm talking about!!! :bigthumb: Wait....I still don't have a tow vehicle.... :1zhelp:

IJ, not sure on what you're referring to "Clutch auto"? I'm familiar with the Lenko, but didn't know there was a similar trans...

As for the cost...Once I have everything nailed down I'll make a post on it. Right now it's still up in the air. I'm mainly concerned with getting it in the car and testing everything out.

Converter/stall info...

This is going to vary from one application to the next. Each converter will be built accordingly to what the individual customer needs. Things taken into account...Weight, Powerband (when does your car start making power? stop making power?), Race only/street only/both?, etc... There are too many variables here. What works for me may not work for you. Therefore, what my converter consists of is pretty irrelivent. Stall is a relative and loosely used term anyway. My converter may stall at 3000 rpm in my car and 2500 in someone else's. It's very dependent on the particular engine and car it's in. Hope that makes sense...

700R4 I have still never been able to get ahold of one. If someone nearby can come up with one I can borrow I'd be happy to pick it up and check into it. The more transmissions this plate will fit the better. It may require a completely new converter design even if the plate will interchange.

 

[oneandgone]

Ken, I was typing my previous reply when you posted. Thanks man, if you thought it was a wild ride other weekend....well, I think this will blow that away! lol!

 

[IJ.]

Grant: Way back when a lot of the Racers modded their Auto's to use a manual clutch! (can't find anything about it online though)

In effect giving them a full manual planetry gearbox that would shift without a clutch once moving!

 

[oneandgone]

Sounds interesting and fun! My boss has a 70 ElCamino with a Lenco in it. I've driven it once with the Lenco and couldn't beleive how easy it is! Thinking about it makes me want to drive it again....Sure wish he'd finish the damn thing!

 

[IJ.]

Sounds interesting and fun! My boss has a 70 ElCamino with a Lenco in it. I've driven it once with the Lenco and couldn't beleive how easy it is! Thinking about it makes me want to drive it again....Sure wish he'd finish the damn thing!

I used to run a MrGasket Vertigate shifter with an M22 Muncie, it got awesome shifts till it killed the synchros!

 

[williamb82]

Grant: I'm kind of sorry I didn't use the CNC to make my adaptor but as there didn't seem to be any interest in a 5 speed Tremec adaptor, I just did it all manually so it's pretty plain compared to yours!

That's the beauty of the CNC Complex shapes are easy and repeatable now you have the code!

dont the t5 and t56 have the same bellhousing bolt patern? and what im getting at is if someone makes an adaptor to bolt a w58 bell housing to a t5, wouldnt it also bolt to a t56? if so how much would it cost for one?
william

 

[IJ.]

William: Nah they use a totally different mounting!

Also the T56 won't fit into the trans tunnel in a Mk3 without some major surgery as the extension housing that holds 5/6th gears is wider than the existing tunnel back there (you'd almost have to move the seats it's so wide)

I posted some pics and details in my rebuild thread here.