I heard that the Callaway TT Corvettes that had autos where replaced with TH400 and a GearVendors Overdrive unit? If this is true, then how did they set the Speedo so it will read the correct speed? Also where could I get a good Th400 from? That has some specs of how much power it can take not " It can handle a lot" :bs REAL numbers

 

The overdrive from Gear Vendors will cost you more than the tranny. I think it is $2300. Lot of info to be found on the swap if you do a search.

 

It is a wonderfull conversion to make on your car. I love mine. I gotta go out to the garage now to go to sleep with it. Ooopppssss, never mind that part. The speedo drive gears are moved from the th400 tail shaft area to an opening in the Gear Vendors unit. Very simple. You can kind of see where the plug for the wiring is near the back end of my Gear Vendors unit in this shot. You can see the shiney plug in the th400 that is sealing up where the speedo gear would be if I didn't have the GV. It is just above the rubber mallet. You may not find a builder that will say, "my th400 will survive forever behind XXX h/p." But that really doesn't matter anyway because no matter what, a good tranny builder can build a th400 stronger than a 700r4. If somebody tells you that they can build a 700r4 to be stronger than a th400 they are a liar. Gear Vendors comes with a 2 yr. unlimited mileage warranty to 1200 h/p. If you have more than 1200 h/p then you just tell them and they will make some valve adjustments up to 2000 h/p. If you manage to break it after 2 yrs. they will fix it or sell you a whole brand new one for $500. Just another note. The car that got 2nd overall in the Car and Driver One Lap last year was a replica of a '63 Grand Sport. The car had a big block and a th400/Gear Vendors. The car was purpose built to compete in the One Lap. Do you think they wanted to make sure the car didn't break down? Same with Callaway and his TT cars. Okay, gotta go to the garage now.



[Modified by Bob86ZZ4, 9:27 PM 2/20/2003]

 

So does your speedo read the correct speed? Also does your ECM controll the converter lock up or does tyour tranny just automatically lock it up at say 2500rpm? :confused: Thanks for the info

 

I had to wire in a box of some sort that Gear Vendors sent me that makes the speedo read out correctly. They were very good about setting me up with everything I needed. The th400 doesn't have a locking torque converter so you just secure that wire/plug up out of the way under the car. The computer thinks it tells the tranny to lock up but the computer has no way to know if the tranny is following it's order to lock up so it doesn't matter.

 

I just posted a question of this earlier, where did you get the mount bracket for G/V to mount to the C beam? By the way for anyone who is thinking about one, I have one in my dually behind a 4L80. Even though that is an O/D tranny, you cannot tow in O/D, but I can with the G/V and that is why I got it. It is absolutly awesome. Anyways I am looking a buying another one for the Vette. However it is a road race car and it will be behind a M21 Muncie, that is why I need to figure out how to mount it.

 

Also the box does not work on 90 and up dashes due to a different speed signal required for the speedo. The speedo is very tricky to be correct at all times. I went through this a few years ago and went through a lot to get the speedo to work under all conditions.

 

How much does it cost to get the Driveshaft shortened? Also how much was your totall cost for a TH400 and a Overdrive unit? ;)

 

Snaketr: I think you would have to contact Gear Vendors to see if they can set you up with a way to mount the c-beam to the Muncie. I bet they could but it might be something special, oh oh, money.

BlownVette: I knew you had some problems getting your speedo to work right. I don't know why because on mine the sender just gets re-mounted into the Gear Vendors unit so it takes its drive from the output shaft so I wouldn't see how it could matter whether the od is engaged or not. Does your sender get mounted in your th400 maybe? Anyway, it seems like they know what they are doing now with the speedo stuff.

Light84: I paid $1400 for my th400 with torque converter. This is from the same shop that builds Al Corda's tranny, big time national champion drag racer. That is with just about every super strong part you can get. Fully manual valve body forward pattern shifting. The forward pattern manual valve body is the only way to have engine braking. Engine braking is absotively necessary for autocrossing and road racing. And darn nice to have on a street driven car. Then, the kit from Gear Vendors was I think about $2500. That is set up to attach to a c-beam on the Vette. They said I should be able to cut and re-drill my stock c-beam and get it to work. I had trouble doing that so I made my own 2 piece c-beam. I love it because I can take apart the c-beam very easily and get it in and out quickly and without fuss. You can look at my web site for some pictures and info about how I made it. Most large metro areas have drive shaft/clutch/ujoint shops that can shorten and balance an aluminum drive shaft. I had mine shortened to 14.25" and balanced for about $100. That included them putting in the correct ujoint on the front to attach the th400 yoke.

 

Honestly I don't remember what the issue was any longer (i did this 4 years ago). I know there was a problem with the 90 and up dashes and that is why Callaway did not offer the trans in those years and went to a 4l60 in the Supernatural.

Also are you sure that the speedo is correct in 3 gear and third gear w/ OD? The reason I ask is my friend had one in his GTA and did not know his was wrong until I pointed out my problem.

 

Yes, my speedo works correctly in all gears. The speed sensor is mounted at the back of the od unit so it takes it's signal directly from the speed of the output shaft. Oh well.

 

We did a swap into a blown 92 several years ago... Very nice, there were some issues regarding the speedo calibration but it was rectified. Gear Vendors builds the O/D unit specifically for the C4's so there's a C-beam mount built into the tailhousing. You just whittle the beam to fit (same as the d-shaft). Only thing I would've changed would be the beam; I think I would've rather built a tubular one instead of "cutting and pasting" the OEM one.

I'm in the middle of swapping a Turbo 400 in my 1990 right now in place of the ZF. Everything is mocked up and I'm just trying to figure out if I should forget the c-beam and fabricate a tranny crossmember or if I should build a damn adapter for the tailhousing to work with the c-beam?? I know there are some that have done just the TH400 swap and would like to see their solutions before I start fabbing stuff. I will probably eventually put a GV in, but right now I drive the car on the street so sparingly it's not worth it.
-Jeb Burnett

 

I still dont know If I should get a TH400 and a gearVenders. I'm not going to be autocrossing but it would be fun to do. Anyway I dont plan to make too much power anyway so If I could get a 700R4 to handle say 550HP I'll be fine. Thanks guys for the replys :yesnod: :thumbs:

 

I guess you need to decide what you want to do and how much of a risk you want to take with your money. I have a 700r4 broken on my garage floor that I paid $2600 for and Art Carr told me, "... it will handle 600 h/p no problem." Well, it lasted all of 5000 miles. I now believe I prefer to spend more money on the toughest parts I can buy. Maybe I should try to sell that 700r4 for a core for somebody, there may be some good parts left inside, I don't know, I never opened it up. Good Luck.

 

Yeah that is a good point, because If I break it, I probably wont have enough time again to change it and it will cost me some good dough. DO you know of any used Gear Vendors Overdrive units? 2500 is a pretty big amount for me right now. :confused:

 

I've never heard of anybody selling a used one. I think the people that have put them in must love them and never want to let them go.

 

Owell, I guess I will just go with the TH400 and an overdrive unit. BTW would there be any linkage problems or anything? Like would the TH400 be shorter so the linkage would be off? I have never seen a Th400 before but I have seen a 700r4 actually a couple of them on a crate but never a TH400 though. Thanks for te help :yesnod:

 

The best way to do it is put in a ratchet shifter, like the B&M Megashifter or something similar. Have you th400 built with a manual valve body forward pattern so you have engine braking, unless the only thing you ever want to do is drag race, in that case build it with a reverse pattern and no engine braking. Either way if you make is a fully manual valve body you don't need to hook up a vacume line to it for the kick down feature that is needed on an auto unit. With the ratchet shifter you won't miss any shifts, it's not possible. It is a very positive shift, you just slam it forward or backward and it will shift one gear at a time. I put a B&M Megashifter in that is designed for the console on the '82-92 F-body cars (Firebire/Camaro) so I needed to do some fabrication/finagling to get it in. The cheezy rubber boot that comes with it won't fit so I need to have a nice leather one made for it, just havn't gotten around to that yet. I don't think you can use the stock Vette shifter because it is made for a 4 speed and the th400 is a 3. Maybe somebody knows how to modify them to make them work. But it still won't be as positive as a ratchet shifter. In the picture it looks like it is kind of high but in actual driving it is in a perfect position. Very natural and quick to shift.

 

Then you must have taken out the the part that shows which gear you are in? Also does that mean that If you put in the 3rd gear that it will start off in 3rd? Could that sometimes cause the back end to fishtail? LIke if I were at the track and I bring first gear to say for example 5800rpm and I change to 2, is their a possibility that the rear can slip out? LIke sideways? :confused:

 

The Megashifter comes with a plate that has the gear indicator showing in a window on the left side of the console. Very much like the stock shifter does. There is no way to miss a shift as far as I can tell. Yes, you could put it into 3rd and start up from a dead stop in 3rd gear if you wanted to. I don't think you ever would and if you did you would just have like no power until you got really moving so you certainly wouldn't fish tail it.