4afe compatible with auto tranny?

[jrpamn21]

Some swap questions to all the technical gurus:

1. Will a 4afe engine mate to my Auto Transmission(AL 25), or are there compatibility issues?
2. Has anyone made a straight rear wheel drive conversion and permanently removed the front wheel drive struts and replaced them with compatible non-front wheel drive front suspensions?
Thanks.

[Neu]

1. Will a 4afe engine mate to my Auto Transmission(AL 25), or are there compatibility issues?

I think it will, just the flywheels are a tad different.

2. Has anyone made a straight rear wheel drive conversion and permanently removed the front wheel drive struts and replaced them with compatible non-front wheel drive front suspensions?
Thanks.

Not that I know of, that might work, but it'd be some wear on the differential.

[pantah]

The rear differential is standard in that the wheel with the least resistance will spin, I believe, like most non positraction type differentials. I am not sure about this as driving with 4WD on dry pavement is not recommended. I am confused. This raises a question, which is: does the front wheel drive work the same way or will both front wheels drive equally? Does the front work like positraction?

I think 4WD is only true on these Tercels if everything is on a dry surface going straight ahead. Comments?

[Neu]

The wheel with the least resistance spins on front and back. I've had my left side locked up and right side spinning away before.

It's not true, true 4wd, but you get all the tires spinning so it is 4wd.

Lockers would be nice, very nice.

[keith]

Neither the front nor the rear are "posi-traction". Limited slip is virtually impossible for the front wheels as the difference between the wheel speeds in front are a lot greater than in the rear during a turn. Even limited slip doesn't proved equal power to each wheel. Its more like a 65/35 with the 35 going to the wheel with traction.

The 4wd does split the power evenly between the front and rear because it is not limited slip, it's like no-slip. But at either end, one tire could just spin. It does work a little better than LSD at one end only.

Early "full time 4wd" vehicles had a regular differential in the transfer case, they were more likely to get stuck that even the old rwd differentials. I used to have a 66 Dodge Coronet wagon with LSD in the rear. I bought a house in a new subdivision that still didn't have paved streets. After a hard rain, the street was really muddy. The building inspector came out to inspect the house next door with his brand new 4wd Blazer. He got stuck in the street in front of my house. I backed out of my driveway with the Dodge and stopped next to him, where the mud was even deeper, waived and drove off. We had paved streets the next week.

Some vehicles use a new differential drive system that uses a worm and roller gear system that works on the principle that a roller can't drive the worm. With this system, about 90% of the power goes to the wheel that has traction. I believe that this is the system that Audi uses in their 4wd. Thats why it can climb up a ski jump.

But even it is not idiot proof. I was in Philadelphia once during a rare ice storm. They get some of snow there but they rarely get ice. I was driving up a steep incline that had a red light half way up. I was driving a Corolla and next to me was an Audi. As soon as the light turned green, he lit up all 4 tires and began sliding backwards, for which his answer was to give it more gas. I use a light touch on the gas and clutch and slowly accelerated up the hill.

[Typrus]

TRUE 4wd means simply one thing-
There is a solid connection between the front and rear drive axles resulting in equal total axle speeds, with no possible differentiation between the combined axle speed of the rear and the combined axle speed of the front.
However, in such a setup, if a given wheel in both the front and rear were to lose traction at the same instant, they could both free-spin, again assuming that total axle speeds are equal, however this is fairly unlikely, resulting in one axle pulling or pushing the other in some situations, also, due to the inability to freewheel madly (although in an open differential setup if one wheel spins its rate is twice that of if both were spinning equally) there is a better ability to regain traction, allowing for better motion.

In a "full-time 4wd" setup (which is truly just an AWD setup, there is a difference as you'll see in a few words) there is one thing that makes the difference.
In an AWD type of setup, there is a form of differential between the front and rear axles, allowing for differing total axle speeds. So, assuming an open center differential (as in early "full-time 4wd") the front axle could be spinning madly whilst the rear axle is doing nothing at all. If the front axle in this situation were to also be open, in some situations you could have one wheel spinning madly and 3 doing nothing. Again, as in the rear open setup, where only one wheel spins the rate is double the rate as if both were spinning. Therefore, the rate is doubled to the input of the front axle, and the speed is again doubled to said spinning wheel. Once it loses traction, owing to this, it is very difficult to regain.
Some AWD setups utilize what is called a viscous coupling. Subaru loves these. In this setup, a thick fluid fills the space between several plates that are spaced very closely, but are not touching (much like a torque converter in the automatic transmission) As power is applied, the thick fluid transfers motion to all plates, resulting in movement. Owing to the lack of a physical connection (though some designs do allow the plates to lock together, creating true 4wd) the two alxes are still allowed to spin at differing rates.
Others yet use a Torsen style differential. This is the aforementioned worm-roller type. HumVees use this. I mean true ones, not the crappy POS H2 and H3 poser garbage piles. This allows for extreme power transfer to the wheel with the most traction, assuming there is still resistance to the wheel with less traction (if it goes airborne, or loses all traction in any other way, it'll just freespin. Hummvee users overcome this with light brake application)

So, in my world, the ideal setup would be an all-Torsen using AWD setup with the ability to lock all 3 differentials. So you have AWD stability and control on the road and extreme 4wd control in extreme situations.


Go to howstuffworks.com and look up differentials. It's actually quite cool.



The transmission mating pattern on the automatic is identical to that of the manual. So, it would "bolt" right up. However, as with the manual's flywheel, flexplate and torque converter clearances might be an issue. Not entirely sure to be honest.

Next big question. Can the old-school 3-speed handle the additional HP and torque? I don't know.

If you did a RWD conversion a GearVendors overdrive unit would be AWESOME on the automatic... My 85 is a real dog compared to my 6-speeds.....


BTW, about the RWD conversion.....

Theoretically, you could just remove the outer cups of both CV Joint assemblies, stuff them in the tranny and hub (tranny to seal dirt and hold spiders together and hub to hold bearing together) and go that way in 4wd. I don't know how the 4wd mechanism works in the automatics, but in the 6-speeds its just a solid mechanical connection, so it'd likely hold that additional force fine. But I believe the auto uses clutches, so it may not hold out....

To use a true RWD tranny you could need to lower the engine crossmember to allow for a straight shot back to the axle. Our tranny drops quite a bit from input shaft to output shaft. I'm not sure if it would, but maybe investigate using an AE86 crossmember? Or else just space ours out or the likes.


The biggest obstacle in the front suspension is holding the bearing together sans a CV. Again, I believe you could just disassemble the joint and shove the outer cup in and bolt it to hold it together. Sounds good in theory, but I've never tried.

[jrpamn21]

Thanks for the input sirs, sure can get a lot of info on this site!