The NAG1 is a special animal. It's a Mercedes unit also known as the WA580 or W5A580. The NAG1 transmission can usually be identified by a round 13-way connector near the front corner of the transmission oil pan, on the right side. The gear ratios are a departure from the ratios found in a traditional Dodge trans:
|2 / 2-kickdown
||1.67 / 1.50
This difference doesn't mean much to the casual observer, but that little extra .59 in first gear translates into more torque hitting the pavement from a dead stop. However, the Overdrive is also not as "over" of a drive as the 545RFE. So, what you gain on the bottom end, you end up losing on the top end (to a lesser extent).
Will your car be running stoplight to stoplight? Will your car spend more time on the highway? How much torque / horsepower will the NAG1 handle without blowing up? Is the NAG1 a more reliable unit than, say, the 545RFE? Will the NAG1 fit in my car? What about tuning? What about Autostick? What's it all worth? These are all great questions that need to be addressed.
Let's take a look at some basics... Power rating? Size? Tuning? Autostick?
How much (real-world) power can a stock 5.7L (because the 6.1L application was built slightly heavier-duty) NAG1 handle?
According to HEMI~C~ on 01/31/2009:
"The stock tranny is rated at 580nm which converts to 427ftlb TQ. This is a steady state rating. I have seen several references from Mercedes that thier trannies are able to withstand aprox 30% more tq on an intermittent basis (lets say 1/4 mile
) which works out to aprox 555ftlb TQ.
Personally, I can attest (going on my third tranny now) to the fact that the tranny was holding up nice until I bumped the power up a notch with a smaller drive pulley increasing the boost and tq to the 595 rwtq level. The pulley increased boost by approx 3psi roughly equating to 50-60ftlbs of TQ. Given the approx power increase, I estimate the tranny was surviving with the larger pulley and approx 540-550 rwtq level.
Something to think about is the fact that there are two other 706.XX trannies available from Mercedes that have higher tq ratings than ours. One is rated at 750nm and the other at 900-1000nm. Both have the same external case/internal gearing and should be bolt in except for swapping the bellhousing required to mount the tranny to the engine.
I have one of the Southern Hotrod trannies currently in the garage ready to be bolted up to my new stroker. No doubt its going to see a work out with my estimated 625+ rwhp and the additional 200hp shot I plan on spraying. Look for a write up on this in the next couple months as I get the car back to the track."
Last edited by HEMI~C~; 01-31-2009 at 04:51 PM.
That's a pretty decent load, in my book, but there are several ways for a builder to beef up an NAG1 transmission even further. Do a search on the LXFORUMS for "Builder Bill" and see what pops up.
What about size? Well, the NAG1 is physically smaller in every direction than the comparable 545RFE. Will it fit? Most likely, the answer is "yes." There will be a new (longer) driveshaft in your future, but "yes."
Uhoh... What About the driveshaft? There's no yoke! Well... There is an answer for everything if you search hard enough. There are a few companies making custom driveshaft adapters for the NAG1. The one I like the best (simply because one of my Ford buddies uses a driveshaft of theirs on his twin-turbo 9-second Mustang) comes from a company called DSS (Drive Shaft Shop). They will, not only, sell you an adapter, but will also supply you with a full shaft ready to bolt onto your car and handle more HP than any stock NAG1 could handle.
How do I tune it? Well... That all depends on what you use to control the NAG1. We'll get to those other options. But, in stock form, tuning can be done with a DiabloSport or with a Superchips tuner.
What about Autostick? Can I have autostick in my RestoMod??? Yes sir... Yes you can! Now, it may come at a small price, but creativity (yeah, I know it's supposed to be neccessity, but I like my way better ) is the mother of invention. It has been said that you will need a stock shifter from a car/Jeep runnning an NAG1 in order to have autostick. ...Yeah... I don't know that I would agree with this. If I have a shifter that has the correct cable throw to put my transmission into Drive, then I'm halfway to the goal. IF guys can add paddle shifters to an NAG1 THEN I see no need for the the actual autostick control to be on the shifter. A user should be able to control the Autostick solely through add-on paddles on the steering wheel (with some fancy-wiring, of course).
While on the subject of Autostick... It has been said on another forum: "The absolute best thing about the NAG1 (with either tuner) is the complete control the "true" autostick gives, and the instanteous WOT downshifts. The so called autostick on the 545RFE's is not really an autostick and all the WOT downshifts, especially the 4th to 2nd prime, are about as bad as it gets.....takes ~2-3 seconds to figure out what you want it to do."
So... You may be saying: "What's the deal? Why hasn't he gotten to the meat and potatoes of hooking it up and making it go yet?" Well... "Making it go" is the tricky part.
Next come the options...
-Stock TCU setup
-Mopar Performance TCU setup