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68 Hemi Charger + Tremec 5/6 speed

M

Miszny

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Hello

I'm new to the forum (normally I focus on a body mopars and I'm active on fabo).
I was recently asked by a buddy of mine if I can convert his 68 Charger with 727 to manual transmission. He wanted something modern with overdrive, as I have some experience with Vipers my initial idea was to use Viper trans with kit to make it handle more torque, but perhaps there is a better way? I dont want to rediscover the wheel here.
I wanted to use factory pedal assembly and also here I am curious how big of a task is it when I'm dealing with automatic car to start with. Any suggestions for parts?

Basically my question is if someone that put Tremec 5 or 6 speed can help me out explaining what am I looking at and if there is body cutting involved etc.

Car is a 1968 Charger with John Aruzza 517ci hemi in it. It is built to handle, all suspension is heavily modified.
Short movie of the car posted few years ago:


If i missed a topic that deals with my problem, please steer me in the right direction and delete the thread.

Thank you!
 
Talk to Kern Dog! He just got thru his 70 and was very informative about the process.
@Kern Dog
 
I have a buddy with a 68 charger with a 528 Aruzza Hemi. We put in a Tremec long ago and he has had nothing but trouble with it. It shifts very poorly at high rpm compared to an oem trans. He has broken it twice. The last time, he sent it to a place that removed the synchronization rings and now it grinds at every shift. I know they have made some newer models but I don’t think they are much better at shifting.
The biggest problem is the gear ratios. Low is so low, it’s hardly useable. And you have to adapt everything to fit your Mopar. The other option is the Passom 5 speed transmission. They had given trouble in the past but you’ll wait forever to get one. The Passon OD gears for hemi 4 speed are not that great either. They are noisy. The gear spread is too wide so you loose all your torque between 1st and 2nd shift. I’ve installed two sets of those and did not care for the ratios. The third set I TRIED to install, but I don’t want to even talk about that one.
So, what I’m recommending to my customers right now is a good old 833 Hemi transmission with a gear vendors OD Unit install on the back. I’ve yet to put one in a car right now, but I’m told it fits the tunnel just fine if you drop the rear of the trans 1/4” by elongating the holes in the cross member. On a 68, I’m just going to put smaller bolts in place of the 7/16” oem and it should be fine.
What I like about the gear vendors od is the ratios and shifting scenarios. You keep your good low gear ratio of 2.65. If you are in a “ sporty” mode, so to speak, you can hammer the car hard in first gear up to your shift point. Then you can shift into low OD at the touch of a button. Rev it up to your rpm limit and manually shift throughout the rest of the gear range. When you get to high gear, you’re already in OD. When you just cruising, you can engage overdrive at 4th gear. You don’t need to shift into OD at each gear change. We’re not driving an 18 wheeler!
So, hope that helps. I’d love to recoup some money out of this POS Tremec but I’ll have to discloses the whole story about it so I doubt anyone will want it.
 
I liked the idea of Jamie’s 5 speed myself just because I don’t like modifying sheet metal or and I like a direct fit. The thing is you get a long wait time and kinda of pricey but I’d do it. To each their own..
 
You can go to the guy that put more money into the project and get one faster than Jamie, but it cost more. He sells at some of the shows out west. I forget his name. If you read the mega thread on Moparts, it tells all about it. Jammie won’t guarantee it if you buy from John somebody.
 
fastmark said:
I have a buddy with a 68 charger with a 528 Aruzza Hemi. We put in a Tremec long ago and he has had nothing but trouble with it. It shifts very poorly at high rpm compared to an oem trans. He has broken it twice. The last time, he sent it to a place that removed the synchronization rings and now it grinds at every shift. I know they have made some newer models but I don’t think they are much better at shifting.
The biggest problem is the gear ratios. Low is so low, it’s hardly useable. And you have to adapt everything to fit your Mopar. The other option is the Passom 5 speed transmission. They had given trouble in the past but you’ll wait forever to get one. The Passon OD gears for hemi 4 speed are not that great either. They are noisy. The gear spread is too wide so you loose all your torque between 1st and 2nd shift. I’ve installed two sets of those and did not care for the ratios. The third set I TRIED to install, but I don’t want to even talk about that one.
So, what I’m recommending to my customers right now is a good old 833 Hemi transmission with a gear vendors OD Unit install on the back. I’ve yet to put one in a car right now, but I’m told it fits the tunnel just fine if you drop the rear of the trans 1/4” by elongating the holes in the cross member. On a 68, I’m just going to put smaller bolts in place of the 7/16” oem and it should be fine.
What I like about the gear vendors od is the ratios and shifting scenarios. You keep your good low gear ratio of 2.65. If you are in a “ sporty” mode, so to speak, you can hammer the car hard in first gear up to your shift point. Then you can shift into low OD at the touch of a button. Rev it up to your rpm limit and manually shift throughout the rest of the gear range. When you get to high gear, you’re already in OD. When you just cruising, you can engage overdrive at 4th gear. You don’t need to shift into OD at each gear change. We’re not driving an 18 wheeler!
So, hope that helps. I’d love to recoup some money out of this POS Tremec but I’ll have to discloses the whole story about it so I doubt anyone will want it.
Click to expand...

Did your friend install the Tremec 5 speed? TKO? TKX?
I didn’t hear anybody having any problems with the Tremec 6 speed in the newer Challengers.
 
Interesting I was considering one for my 72 Charger .. from Jamie.
 
The early Tremec TKO 5 speeds were a bear to shift at high RPM and almost impossible to power shift.
Installed one back in 2004 behind a big block early B.
I believe the later Tremec TKO's shift much better.
 
Yeah the TKO 2-3 shift takes a little getting used to. I think Silver Sport has a good tutorial on shifting these. A trans rated @ 600 ft lbs behind a 528 Hemi, Good luck.
 
I have a hemi with TKO600. Don't have many miles on the new engine but so far shifts nice at 7500.
 
My bud has one of the first 5 speeds. Not sure but I’m pretty sure it’s a TKO. It’s horrible.
 
Thank you for many answers to my post, great feedback.
First off, I planned to use Viper trans because I cant say a bad word about it, works very nice in Viper but its slow and low reving setup. Another thing is that its not strong enough to live behind that hemi, so I wanted to upgrade it a bit. There is a kit that makes it strong enough and its a 6 speed.
Another way to approach this is basically to get something new from Tremec, I wanted your feedback because talking to tremec I only get the good stuff because they want me to spend the money. Old trans is out of the question, especially after what I read here. Dont really want to put the effort to get frustration in return. We are in Europe so everything we do costs stupid money after shipping and insane taxes (warining for americans to vote smart, socialism is expensive).
The goal of this change is to have more fun out of the car but also to make it more usable, more universal in a way. I dont know if TKO600 can handle the power of this car, its 720hp setup as is right now.

The owner is also thinking about 2x4 sniper efi, but thats another story, car now has no choke carbs so needs time before it idles, just like my Duster with Dominator. I don't care about this but some people do I guess, seems that the owner got tired and wants to drive the car more without issues, cant blame him as long as the car keeps its character.
 
Just a small update. I did some reseach of my own about what to use in this build. Talked to company called Eastisde Motorsports and they gave me 3 estimates with different transmission options. Choice was between T56 6 speed and TKX 5 speed in different finish options.
We will go with modified TKX as it requires less cutting. We will use RXT clutch. Suggested option was cryo treatment of the transmission internals with some other upgrades. I will give all the details once we start this for good.
Before we swicth the transmission I'm upgrading cooling system and will start putting 2x4 Holley Snier EFI on it once all the parts arrive.
I will post some progress updates and photos soon!
 
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