A999 and 360 Magnum

[Bruceynz]

Hi Everyone,

I am still thinking of fitting a 360 Magnum into my 1983 Cordoba, the car is a 318 car, what I want to know and I did ask this in another post but it wasn't sort of in the right thread, so maybe this will help. The build sheet on my car says options D33 - A999 Auto trans and D34 - STD Duty Auto trans. There is no option for heavy duty maybe that's the 727 trans, anyway does this mean it will handle a 360 Magnum engine or am I looking for trouble. I use to own a 1979 Chrysler New Yorker factory 4bb and it had a A904 trans in it, can't quite remember if it was A998 or A999 now.

I would run a better cam than stock, but not huge and an Edelbrock intake and a 4bbl carb.Your thoughts on a 360 Magnum, with a A999 wide ratio, 8.25" rear end with a 3.23 ratio, am I looking at something pretty quick in a 3600lbs car?

Anyone know what size roller cam you can run before you need to change the converter, I want to stick with stock converter.

Thanks
Bruce

 

[slant6billy]

Might I suggest a trans from a short wheel based van. My 95 is a 109 inch wheel based 2500 ( 5 lug wheel). It is a short throw between gears, but the 3.9 V6 is a happy high rever. I've towed some really big stuff with my van- like a 35 foot enclosed trailer. I've also pulled a 69 RR in a 27 foot enclosed. Last August I had all the seals redone in the trans as it was developing a leak. The trans shop was not surprised the trans was near perfect except for seals. They figured the seal went due to lack of use before I bought it in 2008. My point, I'm currently seeking a 94 or 95 trans from one of those vans, because I am very happy with the level of abuse I've put to it and how it has never given up the fight. As for wide ratio trans, I'm not a big fan. My 97 Ram pickup has that type with the OD and it does not have the nice firm shifts of the 999 in my van.

 

[kkritsilas]

Bruceynz/Slant6billy:

The A999 (34RH) is a wide ratio transmission, if we define wide-ratio being a 2.74:1 first gear. The A500 (42RH), which is an A999 with an overdrive gear, is also a wide ratio transmission, as it has the same 2.74:1 first gear. The A727 (36RH), and its overdrive equivalent, the A518 (46RH) have a 2.45:1 first gear, so I guess that is what is being referred to as the close ratio transmission here.

Your 1995 van has the wide ratio gearbox, specifically either the A999, or more likely, the A500 OD version, which was standard on the 1995 Ram Vans with the 3.9L V6. (see Wikipedia reference here: http://en.wikipedia.org/wiki/TorqueFlite#A998.2FA999). This is still a wide ratio OD transmission. so your statement regarding wide ratio transmissions doesn't make sense. The A999 had gone out of use in the Dodge trucks/vans by 1990, so your 1995 van had an A500 wide ratio OD trans unless it was replaced by a previous owner. your 1997 Ram pick up most likely had the electronic A518 (42RE, replacing the A518/42RH in 1995/1996), and the lack of firm shifts could be due to that, or to a low rear end ratio, which combined with the close ratio transmission could have made the truck feel sluggish, or the shifts feel soft.

Getting back to the original question, the A999 should be good for long term use with an engine of 300 HP or less. The 8 1/4" will hold together for somewhat more HP (300-350, depending on who you ask). I think that as long as you are not running slicks, and are not too heavy on the gas on a regular basis, you should be fine long term. If you intend to go drag racing, even occasionally, you may have a reliability problem. Your Magnumengine will probably be making 300-325 HP (360 magnum is 230-245 HP stock, LA 318 4 BBL is 165, LA 318 2 BBl is 130 HP). The car will perform much better with even a stock 360 Magnum, and with your add ons, it should go really well, and should be great on the street.

Keep in mind that while we are using HP numbers to judge the reliabilities of the rear end/transmission, the read limitation on the transmission and rear end is torque capacity.

 

[slant6billy]

Maybe I have the whole short throw and long winding throw backwards. The thing with the short wheel base vans, they did not get the OD option. The button to turn it off is deleted on the dash. I didn't see it on any of the 94 to 97 vans in 109 inch WB, but I did find a 99 with the OD, but after 97 it was a unibody van, so they did make a few changes. Thanks for the clarify on the wide ratio.