Converting a T4WD to RWD

[SynthDesign]

This week, Toughtercel and I hung out for a few hours workin out what would be required to convert a T4WD to a RWD only application. I'm mainly interested in the conversion for my 4age swap. If I start destroying trans', I need an option to handle the power and a RWD platform should give me a few different options for burly transmissions.
Toughtercel is lookin into a 22r RWD swap as he has a perfect running engine and trans out of an early Celica and thinks it can go into a T4WD with a bit of massaging.
Both of us are looking to put more than a 100 plus hp to the chassis so it also becomes a question if our meager 6" rear diff can handle it. We might have to fab in a heavier duty rear end, possibly something with disc brakes.... AE86 GTS rear maybe....

We looked a bit into using some AW11 parts, possibly the front hubs and assembly but decided it would be much easier and simpler to just lathe down and balance a set of drive shaft ends to hold the front hubs together.
That should take care of the front drivetrain removal.
I'm thinkin once the engine and RWD trans is in( custom trans mounts possibly), all that would be left is to mount the driveshaft and hope the rear end holds up. I have no idea if the stock driveshaft would work w/o modification but it can't be too hard if fab'n is required.


Other than that.. what else might we of forgotten?

Anyone else's thoughts?

[Petros]

I am pretty sure the input flange on the AE86 rear axle is slightly larger. You would have to chop off the rear u-joint from an AE86 drive shaft and have it welded onto the back of a Tercel4wd drive shaft and than rebalanced. Or if you are also going to use the AE86 trans, you might just use the AE86 drive shaft, along with the rear axle, but you might have to shorten it.

I am reasoably certain the AE86 rear axle will bolt in fine, I took some detailed measurements of one and it should all fit. The center tread to center tread width was exactly the same as the Tercel4wd. I think the solution to the different bolt dia. can be solved by taking the axle shafts and have them drill 4 new holes on the 100mm dia circle between the existing wheel studs on the flange. And than remove the old ones and install them in the new holes. You would also have to drill the brake rotors with the new bolt circle dia as well.

I was thinking it might be worth considering fitting an IRS suspension to the Tercel. It would be a lot of welding, but it seems to me that putting a set of rear struts off of the AW11 or perhaps adapting some front struts from a corolla front end might also work. This means welding in the strut towers into the Tercel wheel wells, and than adding the lateral and trailing arm mounts. Than we could find a nice heavy duty diff to mount in the center, one that comes with LSD. The Nissan 300ZX are common in the yards now, and this rear end is popular with hot rodders for the same reason-common and cheap (and all kinds of different ratio ring and pinon sets are available for it, as well as LSD). This Nissan rear diff is also used by Subaru BTW. Or perhaps a real heavy duty Celica Supra rear end? This rear end is popular to fit into the AE86 or Celica for drifting, they are pretty indestructible and also come with LSD and lots of different ratios to choose from. Both of these IRS options have rear disk brakes too. The same years Celica GTS has an IRS rear end that does not look too difficult to adapt to the Tercel rear end, there will be some cutting and welding, but only for the mount points. The problem with this rear end is it is getting quite rare, so getting cv axles might become a problem. It would be better to find something that has more common axle half shafts.

If I have more time and budget to mess with such an installation I think it would be worth pursuing. Until I can afford to retire I am going to be stuck with a live axle in the rear of the Tercel.

[SynthDesign]

The AE86 GTS rear end is a bit different isn't it???. Gotta take a pic or two of them side by side once I get the rear end out of my 83 T4WD. Think it would take a bit of quick cuttin and weldin but not to hard to adapt. I got one to play with either way.

I measured 45mm more between the 83 tercel and the 85 corolla solid axle, from wheel mounting to wheel mounting. The Corolla is 4x114.4 and uses a RWD off set. Someone told me I could swap the axle between the two. Not sure it it's true. The 78 TE78 corolla that uses leaf springs is only 11mm different and share the 4x114.4 pattern

Welding mounts for the IRS 85 Supra rear assembly would be more than ideal....still a big idea for me....sometime maybe.

[Petros]

The AE86 GTS rear end is a bit different isn't it???.

when I pick-up my RWD 4age engine, the guy was parting out a wrecked AE86 GTS. He had the whole rear axle assembly out of the car, it had the factory LSD (he wanted $200 for the axle with the LSD and disk brakes complete). I took detailed measurements with a metal tape measure, and compared it to my '84 Tercel4wd. As accurately as I could measure everything matched. It still had the tires on the axle so I measured from the center of the tread, tire to tire. It was exactly the same as my tercel, that had the stock 13" wheels at the time. now it is possible the wheels on the GTS wheels have a different off-set, but the wheel to wheel width was the same. And all of the other measurements for mount locations were the same too. It was clearly a heavier housing with the larger center carrier, but all the mount points measured the same. This would make sense if the Tercel rear axle was the same from the rwd corolla, I can not see they would have put a different set of rear mounts on the GTS version, that means engineering a whole new body pan for that one model.

I would have bought the rear axle if he did not want so much, I thought $200 was a bit high, and I did not have that much money. I would have paid him $100, but he said he already has someone who was going to pay him $200 for it (may have been BS, but I did have that much at the time). The car it came from had over 180k miles on it, so no telling what kind of shape the LSD was in, and it would have had the 4.3:1 rear ring and pinion set. I would have had to track down a 4.1:1 ring and pinon set and buy a shim kit and re do the whole diff. And than use the different rear wheel bolt pattern, until I can afford to pay a machine shop to install the 100mm lug nut pattern no the rear axles. So I let it go.

An IRS rear end would really improve ride and handling, almost all newer cars have gone to IRS. I wonder how hard to find the rear end from one of the rare All-trac Celicas, and if it would be a reasonable swap. There has got to be something that is plentiful, rwd, and with an IRS rear end we can adapt to fit.

[4wdchico]

The Miata IRS rear axle/suspension assembly is reputed to be held to the unibody by 6 bolts. We already know that Miata wheels work nearly perfectly on a t4wd so bolt pattern and offset are a non-issue. The rear track is 56.2" as listed in a 1990 year repair manual. Parts are plentiful and cheap. Springs, shocks, diff gear sets and LSD units are available in a vast array, both stock and aftermarket. The '94-'97 standard tranny and the 2000 & up automatic Miatas are a 4.10 diff ratio if my info is correct. I'll go measure the rear track of my '85 t4wd in the am as I could not find it listed online readily.

Interesting link about Miata rear axle power handling:

miataturbo.wikidot.com/differential

Apparently, the 7" R&P set that comes in the 1.8L Miatas rear axle is the way to go.

[Petros]

Good info there! Road and Track mag review lists the rear track as 53.1" (the front is 54.3") With wider wheels it might be as wide as 55" which is still narrower than the 56.2 of the Miata. That much extra width means you would need some very different wheel off-sets, or fender flares in the rear. I wonder if the earlier Miatas were narrower in the rear, the cars were smaller. Sounds like according to that link we might want to find the larger 7" diff, or an RX7 diff. especially if we are doing the 4age swap.

The old '85 Celica GTS IRS required only 4 large bolts to hold the whole assembly in place (they went in vertical through the floor), and it appear the rear spring and shock mounts are in the same place. Than there are 4 more bolts to hold the diff housing in place. the track is pretty similar to the Tercel. These cars are so rare though you could get stuck for parts for the rear end.

[4wdchico]

Not so sure that the '85 GTS Celica IRS is all that rare. Isn't the Supra IRS of that era the same basic assembly?

[toughtercel]

Ha, I am going have to read this input several time to understand the feedback , there seem lots of option for rear diff housing , the rear diff gear have to be strong for high HP or Torque output ,I have 81 Celica and last generation body style , I better start check it out this rear diff and share our homework . thanks guy , P.S. if things go well, i better start looking for another T4WD in the state with blowen motor as cheap to buy.

[shogun]

if it was me doing the work, id do a hilux/tacoma rear end(we have tested them with 500hp+) a w55 and use the ae86 struts, even better because you would have a lot more options for suspension, and it would keep the balance of the car almost the same, a very good time to go to 5 lug wheels also if you´re not planning in machining the rear end for 4 lugnuts

ps. this setup would be pretty much bullet proof in our cars

[4wdchico]

I just measured my rear track on my '85 t4wd that is equipped with Miata daisy wheels. I got closer to 53.2" so very close to the printed measurement.

While looking under the car I got to thinking that most who did a Miata IRS (MIRS hereafter)swap would be looking for stock or higher ride height on their t4wd. This would result in the center line of the IRS ring gear being mounted lower below the chassis compared to the Miata correct?
When looking at pics of the MIRS I noted that the rear control arms pivot just outboard of the diff housing. This kind of IRS is usually designed to increase camber as the outer wheel is driven upwards by body lean, or both wheels are driven far upward by a large compressive force, correct? So, is it possible that the MIRS would tuck the rear wheels upward and inward into the stock t4wd wheel wells upon deep compression? So, it might also be possible, that the MIRS, being a tad longer, might be a good thing because it might have been prone to bring the inside of the rear tires into contact with the body, upon deep compression, of the t4wd if it were the same length as the t4wd axle.

[SynthDesign]

Back on track.... so besides the front axles and swap'in to a stronger rear end, what else for RWD?

[4wdchico]

An ae86 Corolla engine cross member might be just the thing. it would get the engine down a bunch so that the T50 5 speed ae86 tranny could bolt up to it. Lowering the center of gravity would also be a nice side benefit. Direct bolt up for any A series engine.

I have an AE86 cross member down in the basement of my folks place. I will measure the bolt pattern of the mounting holes for you when I'm down there next week, if you want. It bolts to the underside of the unibody rails just like on the t4wd, so there is a possibility that it will bolt right up. My cross member is spoken for already, so please don't think I'm promoting the concept just to sell mine.

IIRC, the AE86 cross member has the mounting points included for the tension rods also, this would make going with a full ae86 front suspension swap a possibility. Tons of options and upgrades are available for the ae86 chassis.

[shogun]

as far as i remember the cross member can be the same, the geometry of the corolla one would put the engine too far back, then after that i guess you would just have to find a way for the gear lever to fit properly in the car because most of the real work would have to be in the rear end welding the brackets for the 4 link, i would also look into a previa rear swaybar so its a little more tail happy, that is my personal preference though, its more fun to drive that way steering with the accelerator

[toughtercel]

the geometry of the corolla one would put the engine too far back:
How far back toward the firewall ,might be good for larger motor for me to install even if I have to cut the firewall to make room .

P.S. I have some pictures to input but keep failing , i have done other forum no problem but this one ahh , ( i try into browse,add the file then it went into HTTD) could someone please explain, other wise i am gonna have to take nerd classes

[dlb]

toughtercel, i do this to post pics:

- make a photobucket.com account
- upload your photos there
- write your post on the tercel4wd.com forum
- when you want to insert your pic in the post, copy and past the IMG code for that particular pic from photobucket.com (IMG codes start with "img", have a url in the middle, and then "/img" at the end.)

go for a 600x800, or 'small' resolution and your pics should fit fine. i've had no problems using this method to post pics.