T-56 on smallblock

[Freddie]

Anyone ever tried to fit a T-56 6-speed gearbox in their 70 challenger with a 340??
any info about possible problems would be appreciated BEFORE the wleding/grinding starts!

Happiness is 200MPH!!!!

[volare360]

i was thinking about a 340 6-speed 86 daytona rwd conversion
however the cost of alot of the stuff is stopping me
either that or a stealth rt twin turbo conversion would be interesting
also too expensive right now
unless i win the lottery LOL

[turbododge]

I installed a Richmond 5 speed into my 70 Challenger several years ago. It required some minor tunnel work to make it fit. The Richmond uses the hemi spline, so you can use a hemi disc. The bolt up holes are really tough to get at on the Richmond, and since I run a Lakewood bell housing, I just used the alternate mount up holes on the transmission and drilled and tapped the Lakewood.( with an extra nut welded to the inside). I am using a Leonard Long shifter for a Z28 that I modified to fit. It comes up thru the original boot and uses the original shifter handle. The rear crossmember requires a new tranission mounting that can be done very easily. The output of the Richmond is the same as a Turbo 400, so you need a Turbo 400 yoke and conversion joints to the drive shaft. The speedo is also Chevy, but you can get a simple gear box with the correct connections to run the stock speedo. If you want backup lights, you need to add a switch. This is a wonderful, and not to difficult, conversion to do. I assume the new Richmond six speed would be essentially the same procedure. Remember that the Richmonds are 1 to 1 in high gear, but have super low, low gear, so you would need to change rear gears to reduce highway RPM. I hope some of this helps!

[Freddie]

Well thanks for the reply; ive' got a T-56 six speed lying around and i thought id' use that, but after measuring the mounting size i realized that the T-56 s a real pig to fit.. twice as bulky as the richmond 6-speed and the gearing is spaced too far. So i guess i have to break the piggybank and get a richmond 6 speed, if its' that easy to fit. Maybe even a 5-speed, need to be geared for 200MPH in 5'th though. Probably a set of 2.73 or 3.00 gears would do. what kind of gears are you using? im' using 3.23 at the moment, and it gives me almost excactly 160 MPH in top gear at 6500, but to be honest with an 727 automatic and no bottom end power it accelerates worse than a 78 volvo estate (well, maybe not that bad) between 0-40 MPH. Since i cant' go faster than 160 at the moment, would be nice to know about any aerodynamic difficulties past 160 (like if at 170 the challenger becomes airborne), though i have a front spoiler and a dual wing on the boot (to be honest again, it doesnt' make that much diffrence at 160 with or without wings/spoilers, only more wind noise!) Also interested in your turbo/efi installation, well impressed with that feat!
custom turbo/efi installations are not exactly what you call easy!

Thank again, time to call summit!
Freddie
Happiness is 200MPH!

[turbododge]

Hi Freddie: Current gearing is 2.76 in an
8 3/4 rear. I set up to keep my RPM under 6000, and prefer 5500 max, for driveability at lower speeds. I found that when the Challenger was relatively stock, it got very unstable at 100 mph. With all the mods it is very stable to 140 ( when my own "chicken factor" kicks in ). Of concern to me is that my front spoiler is large and fiberglass, and ever though it has been reinforced with aluminum sheet, I get worried that it might tear off. I know the loads are high, as the car actually squats at over 100. If the car were to lose a spoiler at 140+, it is possible that the front would get way to light for control, even if the spoiler didn't shred a tire. Form your numbers, it appears you are running about a 27" tire in the rear. My calculations show that a change to 2.73 gears would give you 190 mph in top gear. The 6 speed is a true overdrive, so if you had a .75 over drive gear,you would be able to get 213 out of your current 3.23's. A change to 3.55's would get you 194 mph with the .75 overdrive, and really help your bottom end. In overdrive, you would be running on the countershaft, instead of straight through, so it might cost you some efficiency. Let us all know how all this turns out, it is very interesting, 200 mph is very fast!

[This message has been edited by turbododge (edited February 25, 2000).]

[Freddie]

Thanks again for the info; getting to 200MpH is definetly easire said then done, though. To get up to 200 on normal roads safely means at least 700bhp, mainly because of the drag past 170.. no problems getting to 170, but after that we are talking about 4 times the drag per every 15mph or so, and the roads dissappear rather rapidly at those speeds! im' only running around 460bhp at the moment, thats all i can get out of my "x" heads, but a set of edelbrock heads flow as good as my fully ported "x" heads out of the box! should be able to get around 500bhp and then im' planning to use 125hp nitrous. Should be enough! Well, at the moment im' just stocking up on parts for the last modifications which i hope i can finish during the winter! How much power are you getting out of your 340, and what kind of turbo/efi are you using??? sounds like just about the coolest setup ever on a challenger!

Freddie

Happiness is 200MPH!

[turbododge]

Freddie--The Challenger has never been on the dyno, but best guess is about 600hp at 12 psi boost, which is about as high as I can go on pump gas and 8 to 1 static compression. The turbos are Air Research rebuilds that were sized for the application. I don't recall off hand what housings and impellers are in them. The intercooler is made of two smaller Garrett units welded together to flow enough and still fit in front of the radiator. All the rest of the system is homemade, including the exhaust manifolds. The fuel injection system has been a fuel only DFI for the last 8 years, but I am in the process of converting it to a Speed Pro fuel and spark system, with wide band O2 sensing. This system should be able to run closed loop at full boost to a programmed in air-fuel ratio. Hope it works as well as it appears. Good luck on your project and keep us posted how it is going.