1990 Cummins Build,, yep finally moving up!!

[rikinwyoming]

We are both happy with the trade which is all that matters... I have been around offroading and rockcrawling all my life so I believe that things are meant to be changed and customized to the usage intended. I am looking at cutting off the flatbed at the rear leafs and putting 45 degree cuts as well to make it more offroad friendly, just haven't finalized the design as of yet. Also have to find a good source to change the ring and pinions (want something more efficient for the 35-37 inch tires I will run, and to add front/rear selectable lockers as well). The large front bumper is on and I intend to keep it there. Paint is coming, I am leaning toward to making it red again.... red and black is always a good combo...

[Wyo-M880]

Dana 61 regear techhttp://ramchargercentral.com/technic...-gearing-info/

[rikinwyoming]

Pic of the bumper in question which I re installed,,, yep it's staying ...

[rikinwyoming]

Ok, now a few questions for the people in the know...

The cummins seems healthy albeit I need to do an oil change this coming weekend... other then that healthy! The A727 tranny seems to shift pretty fast, as it is in 3rd gear at 40 mph even though the axles are geared at 3.07's in the pumpkins and the 35 inch bfg's....

What I would like to know, isn't a gear ratio closer to 4.10 more appropriate for the large tires I am running? The diesel seems to be getting around 14 mpg currently. Also, should the A727 be shifting that fast, or is this indicative of a problem I am not aware of. Yes I would love to have a 4 spd auto that will hold up to the cummins , but I am not aware of a direct bolt on option. Lastly, I was going to put amsoil in this beast, but it is very pricey... is Rotella 15w40 good enough with frequent oil changes? Thanks in advance, I want to do this right the first time!

[redthies]

I don't think 3rd at 40 is totally out of line, unless you have it to the floor. For oil, Rotella is a great oil and if you keep on a 3000 mile schedule your engine should be very happy.

[bftank]

start researching the 47rh,

its a 4speed auto came in 94-5 dodges with cummins, minimal electical control, can be built very beefy. has a lockup convertor i believe.

there is also the a518 that came in 91-93 i believe, non lockup convertor has overdrive.

i am a little rusty but i believe the a518 was based on the 727.

redthies-
i think you are think of the later versions of the 47rh, the 47re and the 48re. these are computer controlled transmissions built after 1996 for the 47re and 1999(?) for the 48re. doable but more complicated from what i understand.

cummins forum, 1st gen.org, and compd are great resources for the cummins.

[Spencinator]

My 47re will shift into OD at 45 mph. I have 3.55 gears and 35in tires. Driveablility is fine but I will be swapping in a 5 speed when the truck is paid off. If you add any power and tow you really need to put $3k atleast into your trans to have a reliable auto. The thing that I hate most is how much power I can feel is lost through my 47re. Also not being able to select a gear on hill climbs.

I noticed you said you want to cut the bed shorter. If you keep the bumper on the front its not really worth cutting down the back in my opinion.. You lose your approach angle which wont help your descent angle. Something I would consider doing if I had that bumper is cutting everything off except the main part of the bumper. I would also be a little nervous on cutting the frame of a 3/4ton truck unless you never plan on using it for that rating again. I love the first gen trucks and good luck on your build!

[Saiyan66]

Sounds like you are off to a good start, and looks like a good trade to me. Since you are planning for bigger tires and lockers, I would start by swapping out those Selecto hubs. That is the one part of our old 90 that constantly gave us problems. Everything else was bombproof.

P.S. The A518 transmission is indeed based on the 727, but is an overdrive trans. The 92-93 did have a lockup torque converter to my knowledge. Prior to that did not as I have a 91 and there is no lockup. Still if you are considering transmission swaps at all there is really only one affordable durable option: NV4500. Trust me there is NOTHING like a Cummins with a manual trans behind it.

[4BT]

Lastly, I was going to put amsoil in this beast, but it is very pricey... is Rotella 15w40 good enough with frequent oil changes? Thanks in advance, I want to do this right the first time!

Walmart is your friend when it comes to oil changes. Cummins spec Valvoline Blue is usually available there. Heck, my local cummins dealer had a sale on Blue and it was around $5 a gallon cheaper than Wally World!

[pulltilbroke]

the A518 never had a lock up coverter in the diesels, thats whythe 1stgen auto trucks are so slow. i would toss the auto in the junk and do a 5spd swap.

As far as oil I always run a CI rated oil i my trucks. All this new CJ rated oil has had all the god stuff taken out.