12 Valve With 206000 Miles

[jswanutah]

Brand new to the forum. Used to own an 05 Duramax, Edge, exhaust, cold air.... man what a powerhouse but got rid of it because of the price of diesel and I recently paid cash for a 97 12 valve.... stock. I've put a turbo back exhaust with five inch pipe, cold air and a stage three torque plate. First question.... with that many miles do you figure the trans has been rebuilt before? I get a bit of chatter in lock out now but it's not bad and when I'm towing my RV (27 foot) or my boat (24 foot cutty) it does fine but the power difference from my GM is drastically different. What can I do to this thing to give me some serious power for a moderate amount of cash? I know I'm probably going to end up replacing the trans if I do too much but I want that head snapping power my GM had and from what I've heard these motors are outstanding and at a bit over 200000 miles, it just broke in.... Any suggestions? What should I do first? And by the way, this thing is a work horse, for some reason I love it, the sound, the umph, it says get out of my way....

 

[6.9forddiesel]

you really have to remember the transmissions in the dodges in this gen really sucked i have a 98 2500 v8 and have to rebuild the trans trust me its gonna be expensive i would do it now and build it up before you really mess somthing up

 

[argve]

I don't know what a stage 3 looks like - what does it look like to the plate profiles we have posted here?

Do you have a boost control elbow - this way you can hold off the action of the wastegate until around 30 psi - this will help boost the power.

Have you replaced the AFC springs? This will allow more fuel to flow while still building boost.

With the stock governor shutting down at around 2200 rpms you will want to put in a 3k governor spring kit because there is usable power up there.

The stock exhaust manifold is holding you back as well, plus when you start turning them up the exhaust manifold starts heating and cooling a little faster and so it has a tendency to peal the head off the block on the ends - so installing a 3 piece manifold has two bennies - more flow and allows the manifold a place to expand and contract.

Also the stock injectors aren't doing a lot for you in the power dept as well - I would look for a set of 330's or 370 marine injectors.

then have your timing set to 16.5 degrees

with a set up like this you can still tow but will have decent power.

 

[rebel_horseman]

Ditto to what Travis mentioned. You didn't specify whether your rig is a slush box or a bolt action. If it's a bolt action then the trannie is likely the stocker albeit with a modified 5th gear nut and probably an aftermarket clutch. If you are wanting more power then you'll need a new clutch at some point. If it's a slusher then it may or may not be the factory original. More than likely it's not the original but you never know. I'd recommend a fresh rebuild with a performance torque converter and valve body at the very least, but ideally you'd take it to Suncoast, ATS, etc. for a built trannie.

As far as power, once you really start adding the fuel like Travis said, you'll want to start looking into water/**** to keep things cool. You didn't specify whether you had gauges or not...if not that should be your next upgrade.

But in all of this, you're comparing apples to oranges with the Dmax and Cummins. First, your Dmax had a variable geometry turbo which allowed it to spool very quickly compared to your conventional HX-35 on your Cummins. This alone is a big reason why you're not going to get neck-snapping power out of the Cummins without power braking it first (which puts a lot of strain on the drive train). You're also looking at electronically-controlled and monitored injection events versus conventional mechanical injection. But all in all, I can promise you the Cummins will last way longer and out-tow the Dmax.

 

[averagef250]

The dodge A518, 47RH and 47RE's are actually very good transmissions with a little work. I'd personally take a 47RH anyday over an allison 6 speed. The RH's are very simple and tough with a kit and good converter.

The four biggest things you can do to increase performance dollar for dollar are install a transgo shift kit, install an aftermarket low stall billet converter (you don't need multiple disc unless you're stupid with the skinny pedal), install a 48RE overdrive drum and pack it with clutches and install a 3000 GSK.

The stock dodge manifolds do shrink, but they're fine until you can visually see the end manifold bolts bending in. Aftermarket cast manifolds don't really do a darn thing for you for towing.

You will not believe what a good converter and 3000 GSK will do for you. I don't personally feel the wastegate bolt is even a performance adder. The 12CM HX35 is a poor setup. A 12CM wastegated turbine housing is a restriction on a 4 banger cummins. I have a 12CM WH1C (same as an HX35) on my VE 4BT and can peg a 60 pound gauge below 1400 RPM with the wastegate unhooked. If you want more upgrade your turbine housing to a non-wastegated 14 or 16. With a mild P7100 and stock injectors the 14 would do you better. If you had a VE pump or 330 or thereabout injectors I'd say go for the 16. The VE's seam to spool a bigger turbo easier.

Another dirt cheap upgrade is ditch your stock 180 t-stat and install a 95 chev TBI 350 195 stat. These engines run so much better hot.

5" exhaust is rediculous. 4" is overkill. Mandrel 3" is good for 300 HP. Good 2.5" is good for 220 or so.