Overdrive transmission swap questions....need some input

greasemonkeyman

greasemonkeyman

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Hi,I was considering on doing an overdrive transmission swap on my 1967 Chrysler New Yorker,440 Engine,727 Automatic Transmission.I was looking to get better gas mileage because I may do a little traveling on the highways with it and put some mileage on it,like family vacations,etc.(a few hundred miles per trip).I was told that the A-518 was the transmission to use but have some questions concerning the swap:

Will the engine bolt to the transmission without an adaptor plate?

Can I use the stock torque convertor that comes with the A-518 and will it just bolt up to my flexplate or do I have to change flexplates?

Will my stock column shift linkage work or do I have to modify it for the overdrive gear?

I understand the A-518 transmission is longer than the 727 it will replace,so shortening the driveshaft is going to be needed,but do they both use the same output yoke or do I need an A-518 output yoke to be mated to my 727 driveshaft?

I will be using a good aftermarket transmission cooler,so the transmission lines will be plumbed to that because I think the lines are a larger diameter in the A-518 transmission.

Since the A-518 is a longer transmission(tailshaft area) has anyone built or modified their transmission crossmember and what is involved in doing this? How much further back is the transmission mount compared to the A-518 mount?

Also,are there any modifications to the transmission tunnel required in a 67 C-Body to get the transmission to fit?

I think I've covered just about any and all possible questions about doing this swap,but please feel free to provide any extra input I may have excluded.
I was curious if any of you out there has done this swap and how your gas mileage has been before and after the swap? Is it worth all the trouble or is there a decent increase in mileage?
 
Yeah, you'll have to search for info. Nobody on this board has done it and documented it. If you go through all the pages in the "Engine" forum, there is some discussion, and one member described the swap as the best thing he's ever done. The link Commando gave is a good place to find out what's possible in terms of controlling the trans. If you Google 518 swap, you'll see some stuff out there. There's a really good thread by a guy who swapped into his truck.

You'll need to saw off the bell and replace it, clearance the case, dent your transmission tunnel, and fab some brackets for your shift linkage. The trans mount needs to be moved aft, which has been done by drilling new holes, or (what seems to be the preferred method) cutting your mount and making it fit with a flat Chevy part. Don't know about the yokes.

Do it. Document it. It's on my list of things to do when my motor comes out for a rebuild. Doing the math on gears, I'm thinking 3.23 gears would be a great combination with the .69 OD of the 518.
 
It got a lot easier with big blocks and the new bolt on bell housing lot of fan work we can't tell you what your comfortable with. The earlier the trans the better, less ecu control more hydraulic, but the lock up converter and the od gear itself are both electric so you need to build a simple fail safe vacuum and pressure circuit to do it automatically or do it manually
 
greasemonkeyman said:
Is it worth all the trouble or is there a decent increase in mileage?
Click to expand...

I can answer that real easy.... Nope. Let's say the conversion increased your mileage approx 20%. I think that's a reasonable expectation. If you went from say 12MPG to 14MPG and drove 10,000 miles with $4 gallon gas you'll save $476.

I'm betting the conversion will cost $2000-$2500 to do it right. So 40-50K miles you will break even. Even at $1000 cost, you still have 20k miles to drive before you'd break even.

I do this math ALL the time for people that want new cars because their mileage will increase. It opens some eyes.
 
Your best bet and probably easiest way to get overdrive is the Gear Vendors overdrive unit. Head over to For B Bodies Only as there are some threads on it there. Also there is good info out there just google it.

It's really going to be about you really wanting overdrive. Because the break even point is very high for any transmission swap to get overdrive.

http://www.gearvendors.com/hrdodge3s.html.
 
There is no reason with a tight engine and some good tuning 3.23 and 15 inch tires or 2.94 and 14 inch tires that you cant get 14-15 mpg out of one of these cars on the highway at 65-75mph. I agree with John on this money wise you will never recover from mpg but there are other benefits, the choice is yours and if you have your heart set on 4.10 rear gears (in a c body why?) 2.94-3.23 with a .69 od and tall rubber your 65mph rpm is in low 2000s hard to pull anything that low but flat or downgrade, now if you want to cruise at 80-90 mph steady for an hour I can definitely see it. can't do that here in pa. because of traffic so its not really on my list. However if I ever come across one of these cars at the right time that some dummy stole the engine out of I probably would try to find a 93 up pu or van and pull driveline with F.I. and put it in a good c body, if the 440 or 383 is still in there then that's what I'm working with remember factory timing and jetting was set conservative so that a car didn't come back over and over for adjustments. Do your research and tune it well timing and jetting and you can get the same mpg increase.
 
bajajoaquin said:
Yeah, you'll have to search for info. Nobody on this board has done it and documented it. If you go through all the pages in the "Engine" forum, there is some discussion, and one member described the swap as the best thing he's ever done. The link Commando gave is a good place to find out what's possible in terms of controlling the trans. If you Google 518 swap, you'll see some stuff out there. There's a really good thread by a guy who swapped into his truck.

You'll need to saw off the bell and replace it, clearance the case, dent your transmission tunnel, and fab some brackets for your shift linkage. The trans mount needs to be moved aft, which has been done by drilling new holes, or (what seems to be the preferred method) cutting your mount and making it fit with a flat Chevy part. Don't know about the yokes.

Do it. Document it. It's on my list of things to do when my motor comes out for a rebuild. Doing the math on gears, I'm thinking 3.23 gears would be a great combination with the .69 OD of the 518.
Click to expand...

Mike (Newp) is the expert in this situation. PM him and he'll tell you exactly what you need to do and the walls you'll be running in to.
 
He'll never get his money back in monetary savings no matter which avenue he chooses....
Like Dave said, tall gears (2.71 myself) and 30"+ diameter tires.
 
Economically, I agree.

But some people want to do something different (like put a 4 speed in a formal). :laughing4:
 
1978 NYB said:
But some people want to do something different (like put a 4 speed in a formal). :laughing4:
Click to expand...

But he said......
I was looking to get better gas mileage...
Click to expand...
I was merely addressing that situation.

If he wants to spend an insane amount of money for the learning experience and the satisfaction of it running at 1600 RPM at 65 mph, then go for it.
 
Thanks with all the responses so far.I've checked out that site Commando posted above ( PATC ) and they seem to sell what is needed to do the swap. I'm still open to more suggestions if someone's got other ideas. As far as it being cost effective,that's not much of an issue because I will be doing the transmission swap myself,so there won't be many costs except for welding up the crossmember mount and shortening the driveshaft. I may possibly get a A-518 transmission for less than $200 and if PATC sells their conversion kit for about $50 then it shouldn't be too bad.I'm sure there are other costs/parts needed and I will contact them for more details.With premium gas close to $4.00 a gallon,every bit of mileage helps,but I can see your concern on the overall cost of the swap.Suprised that no one on here has done that kind of swap.I would figure that our heavy C Bodies would be the prime candidates.
 
You're not addressing the bellhousing. That will be the $$.

And shortening the driveshaft... and the linkage.... and the mount. It will all add up to a lot more than you think it will.
 
My question is why?
Where is the return?
At $2500 give or take to do the conversion than may increase your mileage about 30%. So if you are getting about 16 you will now get about 20.8

$2500 will buy you 650+ gallons of gas
At 16 miles to the gallon 650 gallons will take me 10400 miles.

But in 10400 miles I would have spent $2500 and you $4375 (gas and conversion)

At 46000 miles I will have spent $10800 on gas alone and finally you will catch up with the gas and conversion.

If this is your daily driver and you drive 12,000 miles a year it would take close to 4 years to break even.

??

Alan
 
Its about 300 for the ultra bell, money wise who cares there is never enough anyway. Anything less than 3.55 gears and car will become a crappy drive, my 98 ram has 3.55 rears and a 518 auto it turns about 1800 rpm at 60 if I'm not on flat ground or going downhill the truck just slows down then has to downshift to 2nd to get going again gets about 12 on the hwy and drives terrible granted this is a truck but gears are same nothing but a diesel is pulling down below 2000 rpm.
 
MrMoparCHP said:
My question is why?
Where is the return?
At $2500 give or take to do the conversion than may increase your mileage about 30%. So if you are getting about 16 you will now get about 20.8

$2500 will buy you 650+ gallons of gas
At 16 miles to the gallon 650 gallons will take me 10400 miles.

But in 10400 miles I would have spent $2500 and you $4375 (gas and conversion)

At 46000 miles I will have spent $10800 on gas alone and finally you will catch up with the gas and conversion.

If this is your daily driver and you drive 12,000 miles a year it would take close to 4 years to break even.

??

Alan
Click to expand...

How long is it going to take you to break even on your restoration? I don't understand why you're putting all that money into your car when you're never going to get it out again. You would be way better off buying a modern Crown Victoria, because it will be in better shape, and all the parts are still available.

That's how the math works out, anyway.
 
bajajoaquin said:
How long is it going to take you to break even on your restoration? I don't understand why you're putting all that money into your car when you're never going to get it out again. You would be way better off buying a modern Crown Victoria, because it will be in better shape, and all the parts are still available.

That's how the math works out, anyway.
Click to expand...


The original poster indicated that this was to save money with better gas mileage.


I will more than double my investment the second I sell that car but that is not why I am restoring the car. I am a Mopar guy not a Ford guy, it is newer than 1975, I could go on.

Most of us know we will be negative on our restorations and do them for the fun of it or to have a car we may not be able to afford to buy done.


Alan
 
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