A518 vs. 727 questions

[DPelletier]

OK, I will admit that my question has nothing to do with a diesel pu, but it is a Dodge and I knew you guys could help. Apologies in advance.



I am thinking of putting an OD transmission in my '70 Super Bee so I can run 4:10's and still drive on the highway at a reasonable speed.



From what I can gather, the 727 and 518 are basically the same transmission except for the addition of the overdrive unit. I also understand that the bolt pattern is different betweent the Cummins and my RB, but gasser trucks (2wd, of course) should have a 518 that will bolt to my engine.

I can deal with a custom transmission mount and driveshaft, but hopefully the transmission won't require any modification of the driveshaft tunnel, because that is out of the question.



- What would I need to control the OD? a hidden switch perhaps?



- Weaknesses? If the transmission can stand up behind the Cummins, then it should be OK behind my 440 6 Pack. I estimate power to be approximately 450hp and 550 ft lbs.



- anyone know if I can use a regular 727 torque converter?



and lastly, any other thoughts or suggestions?



Thanks,

Dave

 

[fox]

You will find your answers at this site. Mopar

But I will offer some too. There is two types of 518 trannys, Onw with a lock-up converter and one with out. Either can hold the Big block.

The adaption can be done two different ways. You can either get an adapter plate kit, ot you can but a bellhousing to adapt to the case of the 518.

I like the bel housing swap. A place in Jacksonville Florida makes them. I think it is J W ultrabell.

The OD and lock-up ( if used ) will both be controlled by switches. The lock-up must be disconnected while slowing to a stop or the trans cannot shift down. This will stall the motor. So the switches need to know when the throttle is at idle, to disconnect things.

Which converter you use will depend on the trans and whether it is a lock-up or not.

Some of the Dodges need trans tunnel mods to fit these trannys but I don't think the 'B' body does, so it should go right in.

I'd suggest using the lock-up version unless you have very low gears. You need a stall speed that is lower than engine RPM at 55 in OD or it will slip and over heat the trany fluid.



It looks like a great Idea !!!!

 

[DPelletier]

Fox,

Thanks for the info. From what you're saying, I need some sort of adaptor because they never used an RB with the A518, only a small block (360)?

I never thought about the lock up being required due to stall speed. I just figured that a lock up converter is primarily about mileage and with my set-up, mileage is somewhat irrelevant! I was hoping to use a regular 2500 stall 727 converter with my 4:10's, but I see your point.

I obviously have some issues to consider, but it sounds do-able.

Thanks

Dave

 

[TKingsbury]

I think it would be easier to put a Gear Vendor on your existing trans. From what I have seen, they fit better. I believe if you use the 518 you will have to do alot of tunnel and trans crossmember mods. These transmissions are alot chunkier in the mount area, what used to be a skinny tail housing is now the OD unit. By the time you do the tunnel massaging, buy an adaptor bell and get a trans and build it you will have a ton more time and money in it than an add-on unit Like was stated before, you will need to figure out your cruise rpm in OD and get a convertor with a lower stall speed if you go with an add-on.

Travis. .

 

[DPelletier]

Thanks Travis,

I'll do some more checking on the GV idea. The car is too valuable to start cutting or modifying the driveshaft tunnel, so anything requiring that sort of work is a non-starter. Bolt on stuff is OK.

I have a metal fabrication company, so my first thought was if I just needed the adaptor bell and a custom length driveshaft, I could make a custom mount that would bolt-up in the stock locations.

This idea of a lock-up converter may further complicate things and compromise my torque converter selection; but I thought the idea had enough merit to justify a little research prior to just rebuilding my 727.

Maybe I just need to go back to the idea of loading my car onto the trailer if I want to go out of town!



Thanks again,

Dave

 

[CLiberty]

You could use a JW Ultrabell
Look on pg #7, p/n 92457. Or you use an adaptor such as from A&A Trans , not sure wich one you would need (6or8 bolt crank), but there are some options, albeit a little pricey. With the JW peice I think you could use a diesel trans as you have to actually remove the entire bellhousing to install the JW part, but the adaptor from A&A would require you to use a smallblock based 518 due to the bolt pattern

 

[fox]

Fox,

Thanks for the info. From what you're saying, I need some sort of adaptor because they never used an RB with the A518, only a small block (360)?

I never thought about the lock up being required due to stall speed. I just figured that a lock up converter is primarily about mileage and with my set-up, mileage is somewhat irrelevant! I was hoping to use a regular 2500 stall 727 converter with my 4:10's, but I see your point.

I obviously have some issues to consider, but it sounds do-able.

Thanks

Dave

Yes, Dodge has not made a lock-up transmission for a big block. Except our Big block CUMMINS !!!!

Also go to the other site and read up about your project. I don't think it is necessary to cut the trans tunnel on a Super Bee.

 

[DieselTweaker]

I also suggest talking to AandA trans talk to Rick if you can, but most of the guy's there are very willing to help, they have helped me out a bunch,,,, and Rick built the transmission in my truck.

 

[DPelletier]

Thanks again, guys



Dave

 

[fox]

Rick at A + A is a great guy. He built one for me several years ago.

Let us know his opinions / idea's.

And keep us informed.

 

[400Magnum]

So, is it possible to just replace the tailhousing from the 727 with the overdrive tailhousing from the 518? From what little I've heard about the 518, that's where all the overdrive guts are, right? Are the bolt patterns the same for the tailhousings on the 727 and the 518?



What about the 618? That's the HD unit used in the diesel trucks, right? Is the bolt pattern for the 618 tailhousing the same as the 518 tailhousing? If it was that'd be a stronger unit to bolt up behind the 440 6 pack that is in this guys SuperBee. If the 618's bolt pattern isn't the same, could an adapter plate be fabricated to make it all bolt together? Just some thoughts I've had because I've been wondering about doing the same sort of thing to a big block B-body that I have.



Any thoughts?

 

["Mad Max"]

DP - the tried and true way is the GV approach. Lots of guys have done that and love it - all bolt up and bulletproof. Plus you'd be able to build the 727 any old-school way you like, and the transmission won't even know the o/d is behind it. That'd be the way to go, IMO. You can even bolt a GV up to an A-833. Also, you'll have to mod your floor either way, and I also think the GV is less obtrusive than the 518. Basically, your o/d would only really be used for getting there and back, but for the track you'd be all 727.

- Sam

 

[cerberusiam]

The 518/618 is essentially the same trans with the additon of a lockup TC. The OD's will swap between the 2 with relative ease. You can swap parts from the 518 all the way up to a 48RE with some changes in the ports and sleeves if so desired.



Swapping an OD onto a 727 case may be a little more work as the governor pressure tube runs thru the back of the case and the OD clutches are in there also and am not sure what that would entail.



The GV route works but the weight and extra size is somewhat of a concern. I think and OD on the trans would be a cleaner install but the floor plan clearances could be an issue. If an OD trans could be installed with minimal mods IMO it would the way to go. All that remains is to get an OD trans bolted to the 440 and drop it in and see whats what.



Someday I guess.

 

[TKingsbury]

An OD off of a later trans will not bolt on to a 727. An overdrive trans will also not bolt into an older rwd car without major surgery. I did a little looking, and while the GV fits better, depending on the car it will require mild to major surgery to make it fit. If the car is a real 6pack, i'd leave it alone. Either put in higher rear gears, taller rear tires (or a little of both), or trailer it to far away events. My . 02

Travis. .

 

[400Magnum]

Well, even if it didn't bolt on directly, couldn't you still adapt the overdrive tailhousing to the 727? Wouldn't it be similar to installing the Gear Vendors unit? All I'm saying is that if someone took a little time and had some fabrication skills, wouldn't it be possible to get an overdrive transmission from a junkyard, remove the tailhousing from it and install it on the 727 in place of the original tailhousing?



I'm just not in any position to lay down over $2000 for a GV unit, and it'd be nice to come up with a less expensive alternative.

 

["Mad Max"]

You could, absolutely... my only concern is the 518's, at least the od's, don't hold up to big power for long. They'll hold up to a mildly bombd Cummins for a while, but (and I'm assuming the main use of the 727 would be hard core drag racing) I don't think the od would hold up to a lot of abuse on the track, even though you wouldn't be using the od function on the 1/4 mile the power still goes through the output shaft. The one thing that owners of modified Cummins 1st gen rigs complain of is the transmission, and, replacing a factory od unit is at least equal to a brand new GV. Again yall, this is just my opinion. I've put my 518 through the ringer under serious towing, but I am VERY gentle when actually shifting the trans, especially going into od. I never, ever, shift my rig into od under big power, ever. And, I'm having a DTT-built 47re built because I know I'll eventually frag the od.

If ya go with a GV, it won't break, it's warranteed, I bet it's less than replacing a broken factory od, and it bolts up clean sheet. Just thinking of the 'what if' scenarios, and how much after that.

Cheers!

- S

 

[400Magnum]

Yea, I've heard enough horror stories about the 518 busting that if I did something like this, I'd probably actually use the 618, at least it was designed to handle the sort of torque that we'd be looking at here from a massaged big block.



I'm the first to confess to knowing almost nothing about automatic transmissions, let alone how these OD tailhousing units would be adapted to fit, I'm just sort of thinking out loud here. All I was getting at earlier was that if GV was able to add an OD unit onto the end of the 727, then there should be some way to make the factory piece work too. If a person knew all the ins and outs of how the GV unit worked, then that'd be a big help to making the adaptation to the factory unit.



It was stated earlier that the governor pressure tube runs thru the back of the transmission. Again, not knowing exactly what that is because I don't know these transmissions all that well, I have no idea how to address the problem. But, it must have been handled somehow since GV figured out how to make this work.



I guess I should dig out my service manuals this weekend and start reading up on these transmissions and try to learn something. I'm sure that there's a lot more to this than I'm realizing, and I'm sure it won't be as easy as opening a kit and following the instructions, but what's the fun in that?

 

[TKingsbury]

The case on the od trans is different. I really see no reason to try to adapt a stock overdrive tail to a 727, when the factory did it all for you. The GV is a stand-alone unit that is hung with a replacement tailshaft housing that is provided with the kit.

Travis. .

 

[cerberusiam]

You will have a tubbed, caged, four link suspension, frame connectored car before you get into enough horsepower to need to upgrade even the stock 518 hard parts. Remember the 518 already had upgraded parts in the planetaries and clutch packs to handle even the detuned gen1 engine. Until you get up over 700 hp and start using 4000 rpm stall converters with trans brakes will you need to worry too much about the 518.



By far the most failures in the 518's were burning up the OD unit and that was generally only when towing heavy. That was a factory screw up in implementation about like the 2-3 bind up problems that didn't show up until you started pushing the envelope. The second most common failure was the aluminum parts getting hammered to death with age and use. The cummins has an obnoxious amount torsional vibration that does not treat aluminum well. The cummins also makes massive amounts of torque at low rpm's and low pressures that contribute failures of stock units.



There is so very little difference in the hard parts between the 518 and 618 that it is neglible. The reason they held up better, better being a relative description, was the lessons learned from the first 4 years of autos behind the cummins. Case breakage from just engine torque are rare. More often the case is broken as a result of extreme use or an internal failure that takes out the case. If your worried about case strength then the 47RE and 48RE are what you want to build from.



To my understanding the GV unit is totally seperate from the trans and doesn't have a need to interface with it. The governor pressure on the 46/47RH is driven from the governor in the OD and piped thru the case to control shifts. If I remember correctly the 727 has the governor just behind the rear case support and it uses the output shaft, which is hollow to transfer, to the VB. That hollow shaft is a weak point hence the billet shafts for big power applications.



Ironically, the 46/47RH used a solid shaft while the 47RE went to a hollow output shaft. Guess which one causes the most issues when the power levels go up?

 

[smithy]

heres some good info that will help,check it out,www.transmissioncenter.net/dodge.htmscroll down about 3/4 the page to the stuff your talking about