Motor & Trans Rebuild - Need Parts Help

[Chris_94]

We have a 1994 XLT 4-door 4-wheel drive with 4-spd automatic trans and 4.0L V6 engine. Lot of 4's in there.

I've got the extra money and come across a used motor and automatic trans that supposedly runs for $500. Both of them from the same vehicle and have 64k miles on them. I want to buy them and have them rebuilt before I swap them into our truck, which currently has 190k miles and is getting tired. We live at high altitude, in Colorado and we pull a 6x10 enclosed trailer and a small pop up camper quite a lot. The trailer weighs about 2500-3000lbs when loaded and the camper is about the same. I pull the trailer to go fly my RC airplanes. We pull the camper for family adventures in the Rockies. At 10k feet, going up over the mountain pass, she's getting a little slow. Starting to show her age.

What can I do to the engine to make more power but still use the same engine computer? I want more HP and more torque. I don't know where to look for parts to rebuild an engine this new. I'm used to the old 289 and 302 engines. This 4L V6 is something I've never looked into and I don't know what can be done to make more power and where to find the parts.

I'm pretty sure a new set of injectors and a cam will do a lot. A new air intake would do a lot and filter box. Where would I start looking for those types of parts? Does anyone make a small turbo or super charger for these engines? Heads? Cams?

Where would I find beefier transmission parts for the 4-spd automatic?

Not looking to make a 500HP rock climbing beast. It's not a daily driver anymore, but it's driven almost every weekend and on snow days during the winter. Just wanting to add a little more power to the whole truck.

Thanks

 

[arco777]

Searching the forum will yield all the answers you seek. I will answer a couple though.

Parts for rebuild are readily available through many parts stores. I know RockAuto.com has a great selection of rebuild parts for great prices.

Your best bet for towing is going to be gearing. Put a set of 4.10 gears in (swapping in a used 4.10 rear axle is often cheaper) and make sure you run a secondary transmission cooler for longevity of the trans. Coolers are cheap and easy to install, about $40-50 and a half hour installation.

Comp Cams makes a 410 and 422 cam, but chances are neither will help you on an automatic transmission - they're best for manual trans models where you can rev the engine up higher than 3k RPM regularly. Stock cam or even a manual trans stock cam is probably best for you.

Injectors aren't going to make a difference unless something is wrong with the ones you have. You don't want to change injector size (i.e. going from 19lb to 24lb) because without a tune, it won't run right. Stock injectors will support power levels up to and including mild levels of boost.

Computer tuning options are a bit limited for the OBD-I system. You can have Henson tune it in person, or get a TwEECer or Moates Quarterhorse and tune it yourself. Expect to spend at least $200-400 depending on what option you choose for tuning, and without many mods it won't make a difference worth the cost.

Underdrive pulleys are available. That could get you a little HP.

For the trans (A4LD is what it's called) your best bet is adding a cooler, and rebuilding the valve body with a shift correction kit. I used the Transgo SK-Jr A4LD kit and rebuilt two valve bodies with it, and had great results. You can do it yourself with no special tools but a torque wrench. At the same time I added Sonnax upgrades such as the boost valve and governor weight, improving performance and reliability. Also replace the trans filter with a quality unit and adjust the bands to spec. Note that 94 is the best year for A4LD transmissions as they had all the updates.\

Popular opinion on air intake kits is mixed. Some say it's good, some say it isn't. Personally I run intakes on both of my Explorers but it's hard to say if the slight power gain is worth the money they keep costing me in maintaining the parts of the intake.

As far as I know there is no specific turbo kit. You can build your own, search the forums for how other members have done it. The 4.0 is stout and will hold up to boost well.

Supercharger kits such as the BBK Instacharger (roots style) and Paxton (centrifugal) kit used to be made but are now discontinued. They are hard to find but if you have the supporting mods (fuel pump, tune, AFR gauge) they can boost the 4.0 nicely.

For heads, anything but the OEM heads is best. The stock heads from the factory are prone to cracks. Aftermarket-made versions of the stock heads don't have this issue, and will hold up well. I have heard you can mix and match the later OHV heads and pistons to play with compression a bit, but at high altitudes you may want to stick to stock.

So there's a little advice. Honestly besides forced induction, it's hard to make a lot of power out of the 4.0 without spending a lot of money. You might consider an engine swap if you want more power. The 4.0L SOHC version bolts right in with a minor mod to the HVAC box and can even run off the stock OHV wiring harness and computer. Makes more horsepower and a tad more torque. The 5.0L V8 is another option, but takes more work including changing transmission, motor mounts, wiring harness and computer, and transfer case (unless an adapter is used). Work intensive but higher power potential.

 

[jd4242]

X2 everything he said.ill throw my .02 in tho.
GEARS!!!!!! 4.10
engine quest 95tm heads to raise compression to 10:1
Comp cams 410 cam
Smith brothers pushrods
Sealed power rockers
.30 over basic stock rebuild bottom end
Melling m328 high flow oil pump
And all the updated parts and shift kit with an extra cooler

 

[Chris_94]

Thanks guys. I've got to keep the stock trans and motor. I will look into some heads with a cam and some intake/exhaust upgrades. Definitely planning to buy coolers for oil and ATF. If thats not enough then I'll look into the gears.

 

[jd4242]

Thanks guys. I've got to keep the stock trans and motor. I will look into some heads with a cam and some intake/exhaust upgrades. Definitely planning to buy coolers for oil and ATF. If thats not enough then I'll look into the gears.

Skip all that and just do gears....will be your biggest and most felt improvements. What gears do you have now?

 

[arco777]

Thanks guys. I've got to keep the stock trans and motor. I will look into some heads with a cam and some intake/exhaust upgrades. Definitely planning to buy coolers for oil and ATF. If thats not enough then I'll look into the gears.

Oil cooler is pointless in this application. Cams are unlikely to help you with an auto trans without major mods. Exhaust can help a little but make sure you have a baffled muffler. I experienced torque loss with a straight through muffler.

Gears gears gears! Less stress on the trans and motor and biggest bang for your buck, especially for towing.