Best Transmission for AMC 401 and Atlas transfer case

[Jevman]

Lots of knowledge out here for guys like me that haven't been wrenching on things for years and i appreciate it all.

I am dead set on having an AMC 401 in my 78 Cherokee, I have decided I'm going to buy an Atlas 2 speed 3.0:1 and be done with it, I have found a Dana 60 rear axle that appears to be the same width as the stock rear Dana 44 offset axle, two of these things will solve any vibration and the clearance problem on the front drive shaft clearing the 700R4 (which I have) oil pan using the QT (unless you use a non cv shaft). Dana 60 centered pinion will be stronger and bring the angle in closer on the rear, so all this sounds great and my question is, is the 700R4 the right transmission for this and if not, what do all of you think? AMC 401, Transmission ????, Atlas 3.0:1, Dana 44 front 4.89, Dana 60 rear 4.89, 34" BFG, 4" skyjacker lift, Educate me please............

Oh, and what are the best shocks i can put on this so i can drive from Northern Minnesota comfortably and then do some wheeling in places like Ouray?

[dodgerammit]

Personally, I believe it's hard to beat the good old 727. Is it as efficient? No. Does it hold up? Yep. There's a reason I kept the 727 even AFTER the LS went in. I love watching all the naysayers on the FB swap group who claimed I was wasting my time complain about the difficulty getting the speedo to work with the electronic pulse sender on the 4LXXs, and especially enjoy seeing those same people cry about more than one neutral in their 4L60....

However, with that said, given your gearing, I'd wager you're after an OD gear. In that case, my mantra is find whatever is compatible via aftermarket adapters and run it. Just make sure whatever transmission you choose is capable of holding up for what you're realistically going to throw at it and how you're going to drive it. Even if you have to "build it up" a bit.

Oh, and make sure to run as deep a pan as possible with an auxiliary cooler. Burnt or hot fluid is no bueno regardless what auto you run.

[Jevman]

I have a new 700R4 right now, the BJ's crossflow radiator and the adaptor from the engine to trany, 401 will have 400 hP +-, be a driver and sometimes trail thing

[Yeller]

If you weren’t after OD, 727 or T400. With overdrive in the mix 700r4 would be my pick hands down. No electronics and robust. No matter what trans you go with it needs a large cooler.

I have one pushing 380hp/380ftlb that has been living a hard life for 15 years and approximately 80,000 miles, with at least 1/2 of them off road. If it laid down today, it would get an overhaul and I’d smile about it.

[Jevman]

OK, so the cooler on the crossflow radiator is not used and a bigger cooler is put on the front of the radiator or do you plumb them in series?

[Yeller]

Live in the great white north and drive in the winter? Series. Most everywhere else either is fine, there’s pros and cons to both. I don’t have mine in series on any of my built trucks.

This has been my go to cooler for a number of years, this example is an aftermarket clone of a ford super duty cooler https://www.amazon.com/dp/B099JG137Y/re ... ljaz10cnVl

[dodgerammit]

If you weren’t after OD, 727 or T400. With overdrive in the mix 700r4 would be my pick hands down. No electronics and robust. No matter what trans you go with it needs a large cooler.

I have one pushing 380hp/380ftlb that has been living a hard life for 15 years and approximately 80,000 miles, with at least 1/2 of them off road. If it laid down today, it would get an overhaul and I’d smile about it.

This is good to know.
If I ever decide on an OD, I'd prefer a non-electric trans and I know the 700 seems to be a decent trans. They claim the 4L60 is a stronger evolution of it, but I don't recall hearing people having as many issues with it.

I live in the mid south and have my 727 in series through a stock radiator on my wag with no ill effects, but I have some honkin electric fans that move the air through the radiator well.

I dunno if I'll keep it that way once I swap in my crossflow. I can't even remember if it has the built in cooler or not.

[Yeller]

The 700r4 and 4l60 are the same. The 4l60e is the same internally with electronic controls. 4l70e is an upgraded unit that the upgraded parts carry over to the previous units. The 4l70e can be purchased with the “hot cam” LS3 from GM Performance with a warranty so they are proven units. I’ve been around some thumping, stroked 500ci+ big block chevies with 700’s that are happy.

[dodgerammit]

The 700r4 and 4l60 are the same. The 4l60e is the same internally with electronic controls. 4l70e is an upgraded unit that the upgraded parts carry over to the previous units. The 4l70e can be purchased with the “hot cam” LS3 from GM Performance with a warranty so they are proven units. I’ve been around some thumping, stroked 500ci+ big block chevies with 700’s that are happy.

Yeah, I'm aware they are the same. I just have only heard of the more recent 4L60e failures. Most likely, it's like everything else here in podunkville now and due to lack of preventative maintenance. There's a reason I don't buy anything mechanical from the junkyard or off of marketplace. It's complete junk by the time it's available at either place.

That said, I had a 200-4R in a square bodied Caprice and it lasted well beyond 200K before it started leaking out the front seal. Most people consider them junk. An $800 rebuild and it was as good as new. Basic maintenance seems to be a lost art locally.

[Yeller]

Exactly. Years ago when I was in the transmission business everyone always commented about how many 700r4’s we had in the shop. At the time it was installed in every rear wheel drive vehicle offered by GM. The estimate from the industry folks was it was 5:1 of any other single unit on the road. So it made sense that it made up about 40% of our business in our smallish farming and ranching community. Now the 80-82 units had issues, but they were remedied enough that over 40 years later a version of it is still in production. About the only thing that surpasses it is the turbo 400, like the ford 9” it’s been out of production for a few decades but you can purchase a brand new aftermarket unit that makes the original look weak and can be fitted to just about anything imaginable.

[Jevman]

Well this is good info, I tried to pull up your link Yeller and it brings me to my orders on Amazon, I'm sure it's an account thing. Can you guys explain the lock up kits on these things, the guy that built the 700R4 said this one was not hydraulic and required 12 volts to it, is that for a lock up? If so do you need to have a pressure switch inline with the solenoid and a switch in the cab?

[rocklaurence]

Well this is good info, I tried to pull up your link Yeller and it brings me to my orders on Amazon, I'm sure it's an account thing. Can you guys explain the lock up kits on these things, the guy that built the 700R4 said this one was not hydraulic and required 12 volts to it, is that for a lock up? If so do you need to have a pressure switch inline with the solenoid and a switch in the cab?

I believe they are referring to the electric controlled Converter and Overdrive. There are several kits to make this work the way you want. The easiest is that once it shifts into 3rd gear the Converter locks-up. I believe it has a sensor for 3rd gear pressure that activates a relay to lock the converter.
Regarding the 4:89 gears, IMO those are way to low for a 34" tire. With that gear your effectively eliminating OD and the engine will be at 3000rpm at 70 mph. A 3:73 gear would put you close to 22oo rpm at 70

[Yeller]

Well this is good info, I tried to pull up your link Yeller and it brings me to my orders on Amazon, I'm sure it's an account thing. Can you guys explain the lock up kits on these things, the guy that built the 700R4 said this one was not hydraulic and required 12 volts to it, is that for a lock up? If so do you need to have a pressure switch inline with the solenoid and a switch in the cab?

I fixed the link above, I just didn't click far enough into Amazon deep space to get just the part LOL.

The 12v is to activate the lock up solenoid. Depends on how he set up lock up as to what you need to do or may like. If he left it as stock and which version of stock it is just applying 12v could cause it to go into lock up when it shifts to second and stay locked up in 3rd and 4th. Or it could just lock up in 3 and 4th. If not towing I have it only lock up in 4th gear. You will probably want to install a lock up vacuum switch from an early 80's C10, it will cut power when vacuum drops unlocking the converter. Mine is just locked in 4th all of the time. If you do any towing, it needs to lock up in 3rd as well. locking up in any particular gear is accomplished with a pressure switch that grounds when there is pressure in a particular circuit. If you choose to mod those switches, they are accessible through dropping the pan.

Rocklaurence, not sure where your math numbers are from. 3000 rpm with a 700r4 with the selected gear ratio is 89mph. 70mph is at the high end of optimum with an OD but very livable 2368, should be a nice driver.

[Jevman]

I understand, Thanks! It's nice knowing why, how and the mechanics of things your working on. I also bought the transmission cooler you listed above Yeller, looks like it's built well and the reviews are good, now as far as tying this cooler in series with the crossflow radiator, the only problem i see that could happen is if the radiator cracked some in the right spot and let water into the transmission lines, I don't know if this is possible but the more things you add to get one job done, the more things can go wrong, is there a way to monitor your transmission coolant temp or do you just keep an eye out for burnt fluid and shifting problems?

[Yeller]

Glad my spewing information is helpful

Yes it is possible to split an oil to water cooler inside the radiator and do both fill the radiator with transmission fluid and transmissions with coolant, not common but have seen it. I usually don’t do series on them simply to simplify the cooling systems of both, makes the radiator less expensive too lol. You can add a transmission temp gauge, they are easy to add.

Personally I’m a minimalist on gauge requirements. Speedo and fuel I’m good. Simple light for oil pressure, water temp and I’m good. I do like a temp gauge for testing a new system, but an IR temp gun suffices. Life’s too short to stress out watching a gauge, an idiot light will tell you when bad stuff is happening before it becomes terminal and gets your attention quickly, a gauge you may be distracted and not notice until irreparable damage is done.

[will e]

If you can spare a bit more money, get the atlas 4 speed. I have a 2.0/2.72/5.44 and love it. Mine is tucked behind a 401 and 727. If your 700R4 is the same length or shorter your good, if it's a bit longer it will get to be tight.

[dodgerammit]

Glad my spewing information is helpful

Yes it is possible to split an oil to water cooler inside the radiator and do both fill the radiator with transmission fluid and transmissions with coolant, not common but have seen it. I usually don’t do series on them simply to simplify the cooling systems of both, makes the radiator less expensive too lol. You can add a transmission temp gauge, they are easy to add.

Personally I’m a minimalist on gauge requirements. Speedo and fuel I’m good. Simple light for oil pressure, water temp and I’m good. I do like a temp gauge for testing a new system, but an IR temp gun suffices. Life’s too short to stress out watching a gauge, an idiot light will tell you when bad stuff is happening before it becomes terminal and gets your attention quickly, a gauge you may be distracted and not notice until irreparable damage is done.

The most common split failures I've read about or seen concerning the trans cooler inside the radiator is with modern vehicles. The Nissan Pathfinders and Xterras come to mind very strongly. Probably cheap quality pieces used in mass production units designed to save a few pennies on each model. I've not read about anything like that on high quality crossflow models from the aftermarket, though a cheapie, knock-off Chinese model from eBay might be more susceptible. A bit of googling on the model you have would probably put your mind to ease.

Again, if the failures were in a radiator that doesn't normally see them, Id wager it would most likely come down to that neglect of maintenance I mentioned previously.

[Jevman]

Great info, as far as the 4 speed, do you think it's necessary if i won't be using it as a serious offroader and just a sometimes type thing? I'm willing to go the extra but will I use it? will e, what rear axle are you running with that, i spoke with Yeller about a Dana 60 centered pinion on e bay that would be 61" finished out so the guy from Utah says, will the Dana 44 offset factory work ok with the Atlas besides wanting to upgrade to the 60?

As far as maintenance goes, I stay up with that, I like to go over board with everything and try to out flank any problems, thats where you guys come in and why i appreciate it all

[tgreese]

Realize that automatic and manual transmissions are driven differently off-road. With a manual, you use the throttle to control forward motion. With an automatic, you use the brakes. Completely different style of driving with different requirements.

With a manual, you keep your foot off the clutch except when you come to a halt. You need a deep crawl ratio to crawl over obstacles, foot off the clutch. The automatic's torque convertor lets you rev the engine and release its power with the brakes to crawl forward.

You need good brakes and extra transmission cooling with an automatic, but I'd guess that anything deeper than 30 or 40 does not help you much. I would look at how much difference the Dana 300 is from an Atlas, with and without TeraFlex gears.

I'd also repeat that IMO the 700R4 with the 401 isn't doing that much for you in this case, beyond some increased economy due to its better efficiency over the TH400. The TH400 is strong and durable and can be built even more so. Lots of inexpensive aftermarket support too. You could try your combo with the TH400 and see how you like it.

I'd also point out that the opportunity for abuse is much higher with a manual transmission, and I'd predict the lighter axles (Dana 44 or Corporate) would work out just fine. And the front axle is more vulnerable.

Suggest you decide what you want, and make a big table and compare attributes between your options. Unlikely you'll be 100% happy with what you get, even if it's nominally the "best" choice. More important that you complete and drive it.

[Jevman]

I understand, so on my other Jeep, a 360, TH400, QT, 34" wheels and 3.08 (3.54 in it now) gears would be a good set up also, everything stock