4age swap. What needs to happen

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4age swap. What needs to happen

Post by Sgt.Tacticool » Tue Jul 16, 2019 9:12 pm

So I keep bouncing around on what direction I want to take with my t4wd, and I've come to the conclusion that I still have another 60-70 years left I might be able to get to all of them. But the first one I want to do is 4age swap for wheeling purposes (I know the 4age is low torque high rpm, but I'm pretty sure it still has more torque than the 3a.) Now to make this happen and keep my transmission from commiting "turn to putty and shavings" I think I need to regear. The main reason for this is I will also be fitting larger wheels and tires and want the same (or close to) engine rpm to road speed ratio. Does anyone know of a way to regear? Do any of the other Toyota diffs have the same pinion as the Tercel? I figure their are a few options for the rear (including lsds and air/electric lockers, especially if I swap for a truck axle) but I don't know about the front.

This is just the tip of the iceberg for my ideas, some of them will be farther down the line like the truck axle, and I want to build a 7age for torque and economy (as best I can on the latter part) along with a whole host of other things.

Also, anyone that has done this swap, what are some roadblocks I'm going to come across? I know of the steering shaft one and since I'm using 4ages from an mr2 I'm pretty sure the coolant piping is going to be a little bit difficult to route and engine mounts are going to have to be creative but is there much else? Oh and oil pan flywheel and all that. If anyone with experience has some pointers I'd love to hear them!
1984 Tercel 4WD SR5 (undergoing 4age swap)
1987 AW11 MR2 (eventual 4agte build)
1987 AW11 MR2 shell (eventual rally car)
1972-69-76 FJ55 "franken-cruiser"
1995 Suzuki DR350

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My tercel:: 1983 Tercel SR5 4WD
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Re: 4age swap. What needs to happen

Post by BaileySims » Tue Jul 16, 2019 10:01 pm

Blood, sweat and beers.

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My tercel:: '84 Tercel4wd w/extensive mods
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Re: 4age swap. What needs to happen

Post by Petros » Wed Jul 17, 2019 6:11 pm

to make a 4age swap work, there are a number of items that need to be addressed. all of the "hard point" mounts and trans will bolt up fine, but you will need to make a complete custom exhaust header and pipe out the rear (requires heat shields to protect the starter and steering components), you have to either alter the 4age flywheel to take the smaller ring gear of the 3ac, or make the 3ac flywheel into an 8 bolt hub (requires welding up the holes and re-machining). using the 4age flywheel is easier and better since the clutch is slightly larger anyway. you of course will have to make the whole electronic EFI system work in the car designed for mechnaical pump and carb: all new fuel lines, return lines, wiring, ECM, sensors, etc. One last annoying issue is the hood needs to have an additional 0.75" clearance for the manifold in one place, so either a hood scoop, a "lump" or hole cut in the hood, or find a way to lower the engine 3/4" and not get in the way of the cross member below.

you can lower the peak power rpm and raise the low end torque on the 4age by installing the adjustable cam sprocket. you advance the exhaust sprocket timing, and retard the intake cam sprocket, and it move the torque curve down the rpm range. I have seen dyno testing on this engine showing this, and I have a 4age swap planned for a project tercel in my garage, and this is how I am going to make this engine more suitable to off-road use.

if the trans is in good condition, and you use some synthetic performance oil, it should hold up okay as long as you do not abuse it. Perhaps add an trans oil cooler like the off road guys do (requires an electric pump and an external reservoir).

Unfortunately, this is the smallest diff that toyota used so there is no way to up grade it since it is integral to the transmission. there was a model of 4x4 truck, perhaps in the 1980's, that used a similar but larger transmission, but I do not know if that is a viable alternative. I saw one in a transmission shop, and it looked almost the same as the Tercel trans, just larger. I asked the repair guy what it was from and he said a 4x4 toy truck. you might look into it.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)

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