Has anybody used the "PerfectFit" Tremec 5-speed conversion kit for early C4's with the Doug Nash 4+3?
Is it worth the price? Tricky to install or straightforward? Any issues or advice I should know?

It's probably available elsewhere too, but this is the kit I'm looking at:
https://www.corvettecentral.com/c4-8...ransmission%2f

 

I have been kicking around the idea of this, as well. I also see a version of this from Silver Sport available at Summit Racing https://www.summitracing.com/parts/ist-efkc4tkx

If you scroll to the bottom of that page, you can download the instructions. Give that a read and see how it fits with your skills/tools.

 

Sorry, long story. So a few years ago (late 2020), I ordered the Perfect Fit TKX kit from Silver Sport for the 1986 Manual with 4+3.

https://www.shiftsst.com/4-3-to-manu...-corvette/p249

The TKX's were all being manufactured in Mexico, but much delayed, so I waited 9+ months and then they started shipping. I had a pretty low number for the wait list, but they were'nt shipping the close ratio and 0.81 OD I ordered at all. So I switched the order to the wide ratios coming in, and all of a sudden I was like #383 on the wait list. I was getting impatient, said screw it, bought a 1993 donor car, and installed the ZF, including a graft from the tunnel.




About two years later, I started to collect parts for a new engine and checked out the TKX at the Good Guys show, including the Speedway car (1985 C4) that it was installed in. That was not the SST kit, but Speedway's version, and i realized that the sifter was much further forward, and the SST kit had it much further back and to the left.

We get a 10% off coupon from Summit every year for the SCCA membership renewal, so I ordered the Silver Sport "Easy Fit" kit from Summit. Arrived from SST in about three days.

At his point, I had the ZF installed and the 1993 C4 manual trans tunnel grafted in, the magnesium bell housing, Spec flywheel, pretty new Brazilian Valeo clutch and sprung hub, new OEM ZF slave... and the small LT1 starter. Ended up selling all that to ZF DOC (I still have the starter if someone needs one, more on that later)... and got a spun steel Quick Time bellhousing, McLoud steel flywheel, McLoud twin disc clutch, Mcloud hydraulic throw out, and Wilwood pedal pox for the master.

None of the ZF stuff fits, this is why they don't have a "Perfect fit" for anything but the 4+3 as there you can re-use all the flywheel, clutch, hydraulics, bellhousing, starter.

So back to the Summit kit from SST... I did save a lot of money, but seems I got the lesser Easy Fit kit for the 4+3 C4.

https://www.summitracing.com/parts/i...ette/year/1986 I think it was about $3600 plus tax some time last year with the 10% off... free shipping.

It did come with the C Beam Adapter (fits the Manual Trans C Beam) and slip yoke, some hardware. Didn't need the sheetmetal fab stuff that i didn't get anyway, didn't need the Dakota Digital as i already had one for the ZF.

Had to order some of the connectors/pigtails, new front U-Joint, shifter handle, fluids, and some ARP hardware that fit the bellhousing (stuff that came with the kit was too long for the QuickTime Bellhousing for example. For the starter, the small Hitachi or whatever geared starter from the LT1 ZF was not even close to the right location, so I got a nice little Powermaster XS 9502.

Everything bolted up nice, but the bellhousing was slightly deeper (maybe 0.100") so I also made a little bit of a change to the bat wing mounts to move rearward. The shifter was dead center in the ZF grafted hole. Once I filled it with fluid, installed the heavy C-beam adapter, with the hydraulic TB installed, it was about 120 lbs, so perhaps only 20 lbs lighter than the ZF and also had a heavier bellhousing. So my goal of removing 40 + lbs was diminished a lot. More room for exhaust that's for sure.




I haven't driven the car yet, still lots to do, fabricating accessory mounts, exhaust, fuel system components, wiring, power steering, interior, much more.





Hope that helps on the SST Perfect Fit option directly from SSt, versus Easy Fit from SST through Summit or a much lesser kit from Speedway (big differences there too the biggest one was the shifter that comes further back and left)... or another trans shop.

 

I installed the TKX kit that I purchased directly from SST. No issues with anything, great fitment, great instructions, and a great transmission! I have almost 2k miles on mine and its been flawless. I would buy directly from them (SST) if you decide to do it just for ease of warranty if needed and tech support.

 

What rear end ratio do you have, and what gear ratios did you go with for the 5-speed? Is there a 'vanilla' option for gear ratios?

 

My car was a 4+3 so it has a 3.08 in it. The Tremec is close ratio 2.87, 1.89, 1.28, 1.00, 0.68.