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Question about aftermarket 5/6 speed manual transmissions

c.paul9

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I'm an 18 year old kid from Alaska, and I've been working on a 1970 challenger that began life as a 318 automatic coupe for a few years now. Aside from the fact that it's an E-body it's collectibility is virtually zero, so hopefully it won't be too offensive to learn that my vision has always been to fiberglass up a japanese inspired widebody kit and focus on building a genuine performance car with four bar rear suspension and track oriented gearing. I've got a 440 short block with forged internals that I'm planning to get a little over 600 N/A hp out of, but I've had significant difficulty finding a transmission setup that will work with it. I'm not entirely opposed to just buying a transmission built for Ford/GM like a Tremec magnum and getting a local machine shop to make me an adapter plate for it, but I've seen dozens of huge horsepower big block mopars so I'm obviously not the first person to run into this problem. Thanks, and glad to be a part of the community!
 

Rapidfire

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Welcome to FEBO! Great to see another teenager into Mopars! Looks like you have a lot of ambition! Glad your here with us! :)
 

Chryco Psycho

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Welcome to FEBO , great to see younger people here !
Cool that you have a 70 Chall to work on too .
IMO the T56 Magnum from a Viper is a good trans but it will take a lot of fabrication to make it fit correctly , removing most of the trans tunnel & making a totally different trans mount .
You can bolt in a 4 spd OD from Passon , other makes of transmissions are usually not stronger than Mopar ones & most modern cars that still offer manual transmissions are running some version of the Tremec .
I would not spend the $$ on a 4 link generally little if any benefit over upgrading the leafs & sway bars .
 

fasjac

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Welcome from Arkansas! Great to see your interest in the E bodies and muscle cars in general. I have a few friends running the 727 as strictly track cars. And have one running a TH-400. No major issues. IMO it’s about the build. The old Tremec 5 speed works good for my 500 stroker. I do not frequent the track but, thrash on it every time I’m in it. I’m glad you joined the site. Look forward to seeing your build.
 

c.paul9

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Welcome to FEBO , great to see younger people here !
Cool that you have a 70 Chall to work on too .
IMO the T56 Magnum from a Viper is a good trans but it will take a lot of fabrication to make it fit correctly , removing most of the trans tunnel & making a totally different trans mount .
You can bolt in a 4 spd OD from Passon , other makes of transmissions are usually not stronger than Mopar ones & most modern cars that still offer manual transmissions are running some version of the Tremec .
I would not spend the $$ on a 4 link generally little if any benefit over upgrading the leafs & sway bars .
As of now my plan is to go with a tremec, I'll be sure to do some research on that viper trans tho. It sounds like the majority of manual transmission upgrades require cutting the tunnel anyways so it could be a good option. The main reason I'm thinking about the 4 bar in the rear is because I want to be able to easily adjust ride height, but we'll see if I actually feel like coughing up the cash when the time comes. Thanks for the advice man!
 

c.paul9

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Welcome from Arkansas! Great to see your interest in the E bodies and muscle cars in general. I have a few friends running the 727 as strictly track cars. And have one running a TH-400. No major issues. IMO it’s about the build. The old Tremec 5 speed works good for my 500 stroker. I do not frequent the track but, thrash on it every time I’m in it. I’m glad you joined the site. Look forward to seeing your build.
I'm high on gumption but low on cash, so this is probably gonna be a bit of a lifetime project, but I'm sure you guys will still be here when it's done. Thanks for the advice!
 

moparlee

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Welcome to the site from Michigan!
Maybe a long term project, but just keep plugging along as much as you can.
 

sir_veza

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Welcome From Ontario, Canada!
Really happy to read younger folks are also into the Mopar hobby.
If you decide on an aftermarket transmission ensure the driveshaft geometry is correct and not stressing the transmission (which can also) affect the flywheel contact with the starter etc.
As well as strengthening the frame, you might want to pay attention to the shock towers above the front wheels especially if you decide on larger wheels with a low profile tire etc.
Best of luck and most importantly have fun!!
 

70chall440

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Welcome to the site from WA State.

Look into the TKX, its the latest/greatest out there, granted not cheap but is supposed to take a fair amount of HP. That said, you are not the first guy to go down this road and it can be done with a number of transmissions. It sounds like you want a road race car more than a drag car so that will be a little easier on the trans, meaning you probably have more selection than you think. Also, just out racingjunk.com, you might find some beefy race build transmissions there that might work. As far as the adapters, they exist you just have to do some research.

On the 4 link side, I think there is someone who makes a bolt/weld in system for E bodies but I made my own using a generic kit from Art Morrison (local to me) for my 73 Cuda. The biggest problem is that you do not have a lot of space back there and if you want to keep it all under the car (verses cutting into the interior, under the back seat) it can be a challenge.

You did not specify what type of 4 link you are after but from what you wrote it sounds like you would be after a triangulated 4 link (which is what I built). I have my top bars going from the center out at about 40 degrees or so and then built a cross member that runs between the frame rails but is flat to the floor and fully welded in. I also reinforced that bar on the inside of the car. This is the bar that my top bars of my triangulated 4 link connect to.

The next issue is the shock mounting, you cannot use the stock mount as it is because it is not intended to take the weight of the car so you have 2 options; cut it out and replace it with something else to mount the shocks to or reinforce the stock one. This is route I took, I cut out the stock shock mount and essentially modified it but remaking the area that the shock bolts to out of 1/16th plate steel, then I made internal gussets to eliminate flex and then I welded it back into the car. I am using Strange coil over shocks in the rear.

Good luck on the project.
 

70chall440

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Welcome From Ontario, Canada!
Really happy to read younger folks are also into the Mopar hobby.
If you decide on an aftermarket transmission ensure the driveshaft geometry is correct and not stressing the transmission (which can also) affect the flywheel contact with the starter etc.
As well as strengthening the frame, you might want to pay attention to the shock towers above the front wheels especially if you decide on larger wheels with a low profile tire etc.
Best of luck and most importantly have fun!!

I am sure you mean well but driveshaft geometry has nothing to do with the flywheel or engagement of the starter. Bad geometry will/can cause a host of problems ranging from vibrations and odd noises to tearing the transmission apart in extreme examples.

As far as the shock towers go, I am not sure where you got your information but in stock configuration (meaning the torsion bars are present) the shock towers don't care what tire you are running. If you are referring to rubbing or interference due to oversize wheels/tires then he would want to pay attention to the frame and fenders more so than the shock towers. He said he wants to go "wide body" so he can offset the front wheels/tires quite a bit, so this should not be a problem.

Now if you were referring to trying to run a coil over (CO) front end, then I agree with you that the shock towers must be reinforced significantly to take the load of the front end as they were never intended to do that.
 
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