I've got a 1963 Dodge Dart GT convertible.

Is there any way to keep the pushbuttons and use a newer A904 (that will accept a Gear Vendors overdrive), or an overdrive version of the A904 (A508?)?

Is there any other way to keep the pushbuttons and obtain an overdrive?

Gear Vendors unit will only work with a newer A904 or A727 without the rear pump.

TIA

--Walt Jackson

There is no easy way to keep the push button shift with the later 904.
The only possible way to do this would be to machine some special brackets to mount the shift cable above the case and make a real short lever to activate it.
There would be a good amount of engineering work to get the bracket alignment and lever ratio correct.
DD

It's always an honor to have Dr. Dodge respond to the post! Thank you.

I've found an answer to my question.

A company called "Imperial Services" and www.imperialservices.net has manufactured such a conversion, along the lines you mentioned. Cost is $365.00. It's in final testing before commercial release.

Since I will be able to keep my pushbuttons and use a later transmission, this would allow me to use the Gear Vendors unit and a 3.55 rear end = excellent acceleration and good performance and fuel economy at highway speeds.

I wonder, though, if I would not be better off using the overdrive version of the A904 (508?) I know I'd need the adaptor plate that has been discussed many times on this board, but does the transmission crossmember need to be modified? Does anyone make a kit for this?

If not this route, would I gain by using a A904 with lockup torque converter? What year cars did these come in?

TIA

--Walt Jackson

The 904 lock-up I run behind a SL6 drops engine speed 300 RPMs at 40 MPH. It is not an overdrive but it helps.

The only thing I do not like about this gear box is that it tends to "short shift", especially the 2nd to 3rd shift at light throttle. I would also like to increase the lock-up speed to 45 to 50 mph. All this stuff is adjustable inside the valve body but truth is that the box works pretty good as is so I'm not messing with it for now.
DD

The A500 4-speed trans looks the same at the front, but with the overdrive unit in the tail it is much larger in diameter and length. The swap has been done into early A-bodies, but there is a lot of reworking involved to the crossmember and floorpan. I'd say use a lockup A999 with the low first gear and stay with 3.23 gears. You'll get a better launch and still be able to cruise. Look for mid 80's Diplomats, Fifths, and Furys. They are very common and should have the A999 because they had ridiculous 2.4 or so gears for mileage, so they gave them the low gear in the trans.

Any reliability problems with the A999 as compared to the 904? and the $25,000 question, do any of them bolt up to the Slant?

_________________
I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

999s have heavy duty internals, therfore are stronger than 904s. The drawback is "emissions" shift scheduling, ie too early for performance. This can easily be fixed with a shift kit (B+M kit is good). The 999s were most common in the 80's, so most slant powered cars from then "should" have one that will bolt right in. I haven't found a foolproof way to ID one from the outside, though. They look identical to 904s.

The A999 is based on the A727, while the A998 is based on the A904. The 998 and 999 are 3-speed automatics with the wide-ratio gears (which I do not like), heavier-duty internals and a locking torque converter. There is no variant of either of these transmissions that bolts to a Slant-6; they are all the A/LA V8/V6 bolt pattern.

The A500/A518 is not nearly as reliable and durable as the 904 or 727, and as others have mentioned, major-major floorpan rework is required to fit them under an A-body.

If you want the wide ratio, I go looking for an 81 and up SL6 904 as a starting point, most of those come with the lock-up converter.

If I want the wide kickdown band, 4 pinion planetary gears or the 5 clutch disk drums, I go "shake-out" a V8 998 for the parts and just swap them into the SL6 case.
DD

Thanks to Dan for clarifying that /6 998/999 don't exist. However, the 999 and 998 are both 904 derivatives and therefore Doc's idea is the best - swap the guts into a /6 904 case. Manuals say that the 999/998 trans has extra strenghthening ribs cast into the case around the rear servo housing (above passenger rear corner of the pan), so that may be a way to spot one. Excessive rpm drop between shifts is a side effect of the low gear/wide ratio, just like an overdrive 833. So if you put one in a heavy car behind a peaky high performance engine, you may not like it. Lighter cars and milder engines work well with them, though.

Sounds like it may work sweetly in my Dart, if I put in a lower rear end gear like a 3.23. Will I have to work on increasing bottom end grunt to make full use of it, is it noticeable if I don't, or will I just strip the clutches if I try?

_________________
I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

Slants are naturally torque engines anyway unless you've gone whole hog on a race engine. Yes, you will notice a difference, even if you leave the rear end alone. And no, you won't hurt this trans; it uses a 5 disc front clutch and double wrap band, designed to handle the torque of a 360.

in the early and mid 80's was there a such thing as torque behind the 360?