I am doing some long-term planning for my 76 D100 and I would like to take a poll of the currently available options for adding an overdrive automatic transmission. The truck has 3.9 rear gears and a 225/727 combination, and my research leads me to believe I have four options if I want an automatic overdrive transmission:

(1) All Mopar. Find the 60s A series truck/van slant to smallblock adapter setup and run an A500.
Pros: all factory parts, should all fit together easily provided I can find them.
Cons: Hard to find, expensive, the A500 has been described as heavy and not the most efficient transmission. There was the run of aluminum adapter plates made about ten years ago, but those are probably harder to find than the factory cast iron adapter packages.

(2) Gearvandors. Since I already have a 727, I could save up and get a Gearvendors under/over unit.
Pros: Good aftermarket availability and support.
Cons: Expensive. Keeps the unnecessarily heavy 727 trans. If the point is to have a more efficient drivetrain, keeping the 727 is illogical.

(3) GM/Wilcap. Use a 200-4R trans from an 80s era GM product and mate it to the slant using a Wilcap adapter.
Pros: smaller and lighter modern automatic four speed trans, trans should be more avaialble than even an A500. Swap has been covered in detail before by several board members who report good results.
Cons: need to adapt lots of peripheral things (crossmember, throttle and shift linkage), difficulty in finding the adapter plate that is not listed on Wilcap's website.

(4) Creative home-brew solution. Thinking along the lines of a 904 swap with a divorced Volvo Laycock DeNormanville overdrive unit, or making a home-made adapter plate to mate a 200-4R or other modern overdrive auto transmission. Open to other suggestions. These days it seems like it might be easier to find a newer computer controlled trans and use an independent trans computer. But that adds even more cost to the project.

I know it would be simpler and cheaper to just swap to a higher gear ratio in the rear axle, but where is the fun in taking the easy way out?

Any input or suggestions welcome.

If I were starting from scratch, I would first locate the wilcap adapter. If found, I would use a GM 700r4 trans. It has better gearing, better availability and more aftermarket support. All you need is an aftermarket shifter, a kit to control the LU converter, a kick down cable, a fabbed trans mount and driveshaft.

Second option for me would be a 904 and a gearvendors. My 2 cents.

_________________
1976 Feather Duster /6 4sp
1984 W100 318 727 np241
1972 'Cuda 340 4sp
1985 D250 360 46RH

x2 that #3 would be the better option...going 700R4 (these survive easily behind 350's)
You would have to do this with the A500/A518 anyway, since the OD unit is in the tail section...and you would also need to shop for a specific generation of A500/A518 the early versions
up to about '94-ish had hydraulic governors like the A904/A727, sometime after that they used the PROM to govern shifts as memory serves.

Hmmmm. OK, thanks. I was towards the Wilcap/GM trans anyway, and that input just cinches it. Now to find the Wilcap adapter. Thanks.

Just give them a call.

http://www.wilcap.com/downloads.html

I also believe that Gear Vendors haa an adapter for the 904.

True, but gearvendors wants $2900 plus shipping for their unit. Too much for my budget. For that much I could get a junked 360 magnum motor connected to an A518 and update the whole drivetrain. Not really interested in that either, though.

I need to call Wilcap and see what they charge. If it is more than a few hundred dollars, I will just keep a 904 and live with it. It would probably be cheaper to find on old 8 3/4 rear axle for the truck with a lower ratio in it, or even an 8 1/4.

I installed an A518 trans in my '85 D-250 behind a 360. That part was easy. I only had to hammer the tunnel in a few key spots and fab a trans mount crossmember. I could have used a crossmember from an '89-'93 truck with an A500 or A518. I'm pretty sure that x-member will also fit your truck with some re-drilled holes.

I plan to put a slant six in this truck so I fabbed a slant to small block adapter plate. I used a slant block and crank with a pilot bearing installed, a slant bellhousing, a small block bellhousing, a 833 4sp and a piece of 3/16 plate steel. With some careful alignment and drilling with a little welding, I have an adapter plate. I have test fitted it to a small block 727 that I have and it fits nicely. I need to reassemble it with the torque converter and check the run out while turning the crank. It wasn't hard to make. If you have moderate fabrication skills and the said components, you should be able to make your own. I need a truck oil pan and related parts to get this project finished,

_________________
1976 Feather Duster /6 4sp
1984 W100 318 727 np241
1972 'Cuda 340 4sp
1985 D250 360 46RH

Say, wanna trade? I have an extra set of slant truck/van motor mounts, oil pan, and oil pickup.

I don't have any manual transmisison parts (pilot bearing, bellhousings), but I do have extra slant and smallblock v-8 trans cases and extra slants on engine stands. I have played around with the idea of fabricating an adapter, but my fabrication skills are only a little above hitting things with a hammer and I won't have the time in the near future to spend fabricating something like an adapter plate.

I will have to make another one and check the run-out but yeah I will trade. It will take me 3-4 weeks to get it done. Keep in mind that I have not installed and actually ran an engine or tested it for durability. TCI makes a BBM to Chebby adapter out of 1/8" steel so I think it will be strong enough.

_________________
1976 Feather Duster /6 4sp
1984 W100 318 727 np241
1972 'Cuda 340 4sp
1985 D250 360 46RH

The key to getting the proper alignment is using the 4speed trans stabbed in the pilot hole while the small block bell mates up to the raw plate that is bolted to the block. from there you just orient the trans and mark then drill holes.

_________________
1976 Feather Duster /6 4sp
1984 W100 318 727 np241
1972 'Cuda 340 4sp
1985 D250 360 46RH

Cool. Let me know. I am in no rush because I am swamped with work and house maintenance projects right now. The truck oil pan and motor mounts should be loose and under my workbench in my garage, but my workbench is currently buried under sheetrock and I can't double check.

Reed, It's no a truck, but for our 75 Swinger we have an A500 and adapter plate acquired. Just need time to make it happen. It will be Mom and Dad's travelling car. P

_________________
"Louise", a 1976 Dart Custom project, (now sadly reverted to being just an "organ donor" to our other project Darts.)

Cool! I hear that the floor pan needs to be massaged and a trans crossmember needs to be fabricated to fit the A500 in an A body.

A500 and factory adapter would likely be the cheapest, but not easy to find those parts. Plus, the A500/518 are not nearly as well supported as the GM trannys. My first vote would be the Wilcap Slant-GM adapter plate and a GM trans. 200-4R has better ratios than the 700r4, but the 700 or 4l60 are way more available.

Lou

_________________
Home of Slant6-powered fun machines since 1988

Realistically, for me this will come down to cost. Whatever I find first for cheaper will what I go with. I need to save up probably at least $800-$1000 to purchase all parts and miscellaneous bits that need to be changed. I need to have cash on hand to jump on whichever adapter I find first, and then get whichever trans matches the adapter.