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View Full Version : Cross breeding to get just what the Doc ordered



Robyn
11-07-2008, 09:03
Well as many of you have read I am working on a 92 Burb and doing some engine swapping. 6.2 to replace the 454.

Now the issue of a good OD tranny is coming into view.
Lets keep in mind that the goal is to have Zero computers on this truck.

This very requirement knocks the 4L80 out of the game.
The 700R4 is just too problematic and far too costly to build and make even close to reliable.

** I hear all the stories about the little 700 that could. I have built many of these and to do so takes Big $$$ to make them live and even then the parts are tiny compared to the 4l80 or the 400.***

I really wanted an OD tranny so off on a damned fool crusade I went.
Allsion has many trannies out there but none are OD except the new electronic stuff.

Then during a conversation with a tranny parts supplier I found out that the 518 Mopar box of the early to mid 90's is workable without a computer.
Just a little creative wiring and a couple pressure switches and poof, all done.

Currently I have secured a 518 box from a 93 Dodge 4x4 and am working on adapting things so it will fit the 6.2.

The old cast Iron powerglide ring I had in the shop has come to the rescue.
This item with an aluminum plate on the back will allow me to get the engine and tranny to cuddle up close. :D

Currently I have modified the Powerglide ring to let the diesel starter fit in correctly so all is well there. The flexplate fits in fine too.

I am working on a "setup pilot" made from a chunk of 4" steel shaft that when finished will sit in the last two main saddles and protrude out the rear of the engine block allowing me to pilot the tranny case with just the pump.

With the tranny located on the crank centerline I can then locate the Mopar bellhousing bolt and dowel holes.

I get the tranny tomorrow so as soon as its clean and apart, things can move ahead.

Another area is the T case.
The unit I got was complete with the T case but unfortunately the case is the earlier RH drop one.
My plan is to use my 241C from the Burb and machine a reclocking ring to allow it to bolt to the Mopar box.
"Piece of cake"

The input shaft from the Burb T case will have to get swapped with the Dodge unit (32 spline to the 23 spline)

Pretty much straight forward machining and bolt together stuff.

Once the assembly is ready the cross member in the truck will need a tad bit of massaging.

With the huge lift on the rig the torsion bar cross member has been lowered a bunch so it wont get in the way.

The Dodge assembly is a tad longer then the GM setup so the drivelines will need a tad bit of tweeking.
I got the front shaft from the Dodge and it may be of use.

Many have asked "WHY" well there are several reasons.
1 The Dodge unit will allow me to complete the project without electronics and to end up with a strong drive train.

2 Because I can. :D:D:D

This sort of project requires a lot of thinking, planning and calculating.
This in and of itself is good for the mind and it keeps me just happier than a clam at high tide.

When done, will it be cool, probably, depending on ones viewpoint.
Will it work well, most certainly it will.
Will it increase the value of the rig? probably not.

Oddball wied stuff is the things that turn heads and make people wonder.
I like it.

keep you informed and as soon as I have more stuff tangible I will post pix of the parts and stuff as I build them.

My intent is to assemble the entire powerplant and drive train on the floor with all accessories to be sure it all fits and then install it in the truck.

To those folks not familiar with the Mopar trannies, the 518 is nothing more than an old 727 with an OD on the back.
The 727 has been installed in everything from big Imperials of the 60's and 70's to huge motorhomes.

Its tough and can handle most anything you can toss at it.

The OD and lockup, as with most of these must be treated with a little care to keep them alive.

The basic box though is a tank.

It should be interesting to say the least.

OH BTW, dont try this at home. :D OH and for those that will ask about cost, I paid just $125 for the 518 with the Tcase and its in good shape. :D

Keep ya posted

Robyn

6.5 Detroit Diesel
11-07-2008, 10:43
Sounds like it is coming along nicely! I have an idea that it will be a very unique truck when done. :D

Robyn
11-07-2008, 11:45
Thanks for the encouragement. :D

The idea of mixing and matching is certainly not a new one.
In the class 8 truck circle it is the standard. Buy a new Freightliner, Pete, KW or Western Star and you simply sit down with the salesman and spec out what you want.
Front axle,
Rear axles and drive ratio
Brake systems
Engine, Cat, Cummins or Detroit
Type of suspension and manufacture
Accessories and so on.

The heavy duty market uses a more freindly and adaptable set of standards for engines and transmissions so they will all work well with one another.

Do what I propose is certainly not new, it just takes some time and thought.

The auto makers cringe at this stuff but it is not the average girl who does this so its a moot point.

Best

Robyn

DmaxMaverick
11-07-2008, 12:28
Still with you on this, Robyn.

I understand the "want" for an OD tranny. But, if you plan on keeping the 37" tires and 3.73 gears, when would you be able to use it? After doing some math (in the other thread), you'd have to swap in 4.56 or 5.23 gears to get engine RPM and power to even run OD (add to that, all OD gears are notoriously weak, comparatively). That also brings up dead stop acceleration issues. You would be relying on the torque converter for your reduction for take-off. With that in mind, this leaves only a TH400 or Allison tranny as a workable (reliable) option. The lock-up converter you are considering is not the 518's strong feature. They are small, and generate a LOT of heat under load when open.

Robyn
11-07-2008, 15:17
The 4L80 works fine now and the gearing in the Mopar box is very close
GM is 2.48, 1.48,1.00 and .70
Mopar is 2.45,1.45, 1.00 .69
So little difference to even worry about.

The 4L80 works fine now so I am not too worried about the 518 box handling the job.

I had the rig up to road speed a couple times and things were fine.

RPM never got below 2000 at any time even after engaging lockup.

As I mentioned in the other thread I need to check the ratio.

The converter will come apart and have the stall reduced as well as the turbine and pump blades brazed and a kevlar lockup clutch installed.

The stock Mopars were a little loose and yes they did tend to eat clutches.

The size will be about the same as the stock 4L80 converter.

Best

Robyn

Robyn
11-09-2008, 08:52
All is well and the new prize is home.
Today if the weather will allow I will steam clean the stuff and get it ready to come apart.

I was also able to get the Dodge throttle pressure cable :D:D
My first examination of the Dodge cable seems as though it may very well connect to the same bracket and rod used by the 700 R4 from the 6.2

We shall see. If not, AN ADAPTER will be needed :)
Far better me thinks to use off the shelf stuff if I can in this case to simplify things should a replacement be needed in the future.

Got to do some rearranging in the basement shop to allow room to build the complete powertrain up and be sure all the little stuff fits and will work before trying to get it in the chassis.

Pix to come soon ( I hope)

Best

Robyn
11-09-2008, 18:22
Got busy today and cleaned up the new tranny and got it inside so I can work on it.

Pix

Hot water at 180F and 2000 PSI gets rid of all the crud especially with some caustic soap.

The little Scat track makes quick work of lifting stuff around.
Also does a fantastic job of providing a place to hang the airhoist to pull an engine.

Tranny all clean and ready to go inside

Inside and all ready to meet the tools.

Robyn
11-09-2008, 18:28
More pix

I will get at this thing in the next couple days and get it off the hand cart and onto the floor and start breaking it apart.
The transfer case comes right off with just 6 bolts and the shifter.
The OD unit comes off the back of the tranny with a few bolts and then I can rip the tranny down to the bare case and get going on the adapter plate