Reed's 78 Corvette TH2004R Swap

1981Z06Vette

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Woodstock, GA
Here are some pics of a 78 Vette that I recently put a TH2004R transmission in (sorry about the orientation of the pics; not sure how to correct that on here). The crossmember needed only to have the bolt on TH350 mounting portion removed, and the trans attached directly to the crossmember. I did make the ( sections of the crossmember removeable for easier future service, however. I braced up the inside of the crossmember, so its probably at least as strong as stock even with the ( pieces removed.
 

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When I first talked to Reed, it was about an issue he was having with the shifter (B&M Quicksilver). He told me the trans was a TCI TH350 with a reverse pattern manual valve body; way overkill/mismatched for a nice cruiser like this. The convertor in the thing stalled at around 3400, way above where the GM 330hp crate motor starts making power. Overall, it was a case of a shop that had a used transmission they wanted to unload. Great for a drag car, but not for this application. So, I told him about the advantages of the TH2004R swap, and we had one built by Neal Racing Transmissions http://www.nealtrans.com/ on a Monte Carlo SS core. I would highly recommend these guys for ANY GM transmission build. I fixed a lot of minor issues (leaking, mangled cooler lines, etc), but the hardest part was fitting the new shifter: a B&M Megashifter designed for a 3rd Gen Camaro/Firebird console.
 

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If the stock shifter had been in the car still, I would have used it along with a Shiftworks conversion, but it was gone and the guys who put in the TCI trans recessed the Quicksilver into a steel box a few inches below the floor. Fortunately, it wasn't deep enough to cause interference with the transmission case! I thought that this console Megashifter would be the best fit, considering (supposedly made for a TH700R4 or a TH2004R). In spite of B&Ms insistance other wise, there is no way to bolt up the shifter cable bracket to the transmission pan and be able to adjust it (the threaded part isn't long enough to work with their bracket) on a Th2004R. No big deal...I cut apart the bracket, rewelded it, and made it work. A little more work was required on the modified console plate already in the car, adding the plate that came with the shifter. Ideally, I would have preferred to have a new, one piece plate cut on a waterjet, and this may still be done at a later time. I think it looks pretty good as is, though. I fastened it down with black allen head screws, similar to the stock fake screws. Reed used to get horrible mileage (around 7-8 mpg), and also had some mild overheating issues, but he just drove the car to Louisville, Kentucy from Atlanta, GA and back this week, and reported mileage just over 20mpg (with the stock Holley that came on the GM crate motor!!). Drivability is MUCH improved, too, and with the shift kit installed by Neal and a more appropriate convertor, it feels stronger than before (lower 1st gear). Needless to say, he is VERY pleased!

Later this week, we are putting in a set of VB&P 550 springs, Bilsteins, and a "TwinTurbo" spreader bar. More to come!
 
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Nicely done!! I wish my cross member would have been as accomodating! I was able to use my stock shifter though, I just made another notch for the new 1st gear. What converter did you go with? I currently have a 2800 stall, but really don't like the way it drives at lower RPM. I'm thinking more along the lines of a stock stall, say 1900. My engine starts building power at about 1700....
 
Nicely done!! I wish my cross member would have been as accomodating! I was able to use my stock shifter though, I just made another notch for the new 1st gear. What converter did you go with? I currently have a 2800 stall, but really don't like the way it drives at lower RPM. I'm thinking more along the lines of a stock stall, say 1900. My engine starts building power at about 1700....

Thanks! I had thought the crossmember would be the hardest part of the swap, but it was actually the easiest.

Its around 21-2200 RPM. The same guys who did the trans rebuild supplied the convertor (Neal Racing, the link is above). I have used their stuff for years, and been very pleased with it.
 
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