Trans swap help

[1972ChargerRT]

Hey guys I'm thinking of swapping the 722 3 speed in my 72 charger for a 46RH 4 speed. This car is my daily driver and I want to be able to drive it on the highway for extended road trips and get better fuel mileage, and not run the motor at high rpm. Is this a good swap? I run a 3.55 rear gear, full posi. And I have a 27560r 18 rear tire.

 

[BeepBeepRR]

Here is a good read for you.

https://www.hemmings.com/stories/article/chrysler-a-518-overdrive-transmission

 

[ckessel]

What engine do you have? The 46 only fits the small block. If bb. you'll need to modify the front of the trans by cutting off the bell housing portion and getting an Ultra Bell which will then allow it to fit a bb. Several have done that, but not me. You'll also need a way to control the o/d and converter lock up. The front portion of the trans is based off of the 727 but has more girth where the o/d attaches which will require mods to the t-bar/trans x member because it will hit the o/d unit. Also you'll need to fab up a new mount for the trans and deal with the shifter mechanism. I believe Holley and USCT have mounting options available.

 

[1972ChargerRT]

What engine do you have? The 46 only fits the small block. If bb. you'll need to modify the front of the trans by cutting off the bell housing portion and getting an Ultra Bell which will then allow it to fit a bb. Several have done that, but not me. You'll also need a way to control the o/d and converter lock up. The front portion of the trans is based off of the 727 but has more girth where the o/d attaches which will require mods to the t-bar/trans x member because it will hit the o/d unit. Also you'll need to fab up a new mount for the trans and deal with the shifter mechanism. I believe Holley and USCT have mounting options available.

Thanks for the help, I'm running a 360 la motor, and I found pressure switches to control the 46 rh. I'm not going for big power I want reliability and comfort on the highway. My plan in the next few years is to go on a trip to drive all 2442 miles of rt 66 in the car.

 

[ksurfer2]

Wouldn't a Gear Vendors be an easier and less expensive option?

 

[ckessel]

GV is what I went with. Plus I'm running a bb. Once I factored in costs, GV was the way to go for me. Still had to do some work for fitment though.

 

[1972ChargerRT]

Thanks for the help, I'm running a 360 la motor, and I found pressure switches to control the 46 rh. I'm not going for big power I want reliability and comfort on the highway. My plan in the next few years is to go on a trip to drive all 2442 miles of rt 66 in the car.

Wouldn't a Gear Vendors be an easier and less expensive option?

I've looked at the cost and the GV is from my research the much more expensive and difficult to fit option.

 

[ckessel]

On your trans, did it come from a truck or van? Hopefully not a Jeep Grand Cherokee which has the starter on the pass side. Also when you get your converter, make sure its weighted for the 360, not the 5.9 Magnum which is different, or get the B&M flex plate[ looks like a bite was taken out] so you can run a neutral balanced lock up tc.

 

[WileE]

Whew ! ok... it's a mechanical topic...

 

[JoePole]

I think the OP is on the right track. You will need to fabricate/modify the cross member and shorten the driveshaft. If the transmission is in good working order I would highly recommend reaching out to a reputable converter vendor and have a custom converter built that matches your combo. As stated you may have some contact issues with the tail shaft but it is minor and from what I have read you can grind some of the housing for that. Other things are a speedometer cable extension (ebay), shifter (there was a guy here who modified the detents on a slap stik to make it work) and of course OD and lock-up activation (also a guy on FABO who used adjustable solenoids).
With all that said, I have not done the swap YET but have been doing a lot of research. There are plenty of threads here and on FABO. Not terribly difficult but depends on your skill set.

 

[1972ChargerRT]

On your trans, did it come from a truck or van? Hopefully not a Jeep Grand Cherokee which has the starter on the pass side. Also when you get your converter, make sure its weighted for the 360, not the 5.9 Magnum which is different, or get the B&M flex plate[ looks like a bite was taken out] so you can run a neutral balanced lock up tc.

I'm looking for a truck that runs with a 360 in it to just swap as a unit. I'm only looking for 88-95

 

[1972ChargerRT]

I think the OP is on the right track. You will need to fabricate/modify the cross member and shorten the driveshaft. If the transmission is in good working order I would highly recommend reaching out to a reputable converter vendor and have a custom converter built that matches your combo. As stated you may have some contact issues with the tail shaft but it is minor and from what I have read you can grind some of the housing for that. Other things are a speedometer cable extension (ebay), shifter (there was a guy here who modified the detents on a slap stik to make it work) and of course OD and lock-up activation (also a guy on FABO who used adjustable solenoids).
With all that said, I have not done the swap YET but have been doing a lot of research. There are plenty of threads here and on FABO. Not terribly difficult but depends on your skill set.

I was hoping to find someone on here that has already done this swap to give some advice. I've researched it a ton and think for my application that the 46rh will be better than a GV. The crossmember mod is simple and the driveshaft is about $350 to shorten and balance. I'm just trying to get as much practical knowledge as I can because this car is my daily and I want it down as little as possible. Pluss pulling a good motor and trans from a running truck to swap means I can part out the truck to pay for my swap. And then the 360 and 727 I pull out of the charger can go into something like a dart and I can flip that quick.

 

[ckessel]

I don't fully remember, need to see the parts manuals to verify, but the 88/9 may have been non lock up. Pretty sure 90 on is. If you are yard scrounging for a unit, on the 94/5's look for Z as the 8th digit in the vin. 5.9. Y is 5.2. 5.9's had a 5 pinion planetary, 5.2's had 4, 3.9 had 3. One of the many things I occupied my mind with during down time when working dealer parts.

 

[1972ChargerRT]

I don't fully remember, need to see the parts manuals to verify, but the 88/9 may have been non lock up. Pretty sure 90 on is. If you are yard scrounging for a unit, on the 94/5's look for Z as the 8th digit in the vin. 5.9. Y is 5.2. 5.9's had a 5 pinion planetary, 5.2's had 4, 3.9 had 3. One of the many things I occupied my mind with during down time when working dealer parts.

Thanks that will help a ton

 

[ckessel]

Actually, make that for 94-02 on the vin's.