Transmission Swap

[romarvi]

New to the T4wd's, its actually my daughters dream car. Anyway, found a very straight and clean 1984, good motor but the transmission is stuck in 3rd gear. Drives great, just a one speed right now. I have a line on a 1987 with a blown motor that I can pick up cheap, owner say the tranny is good. Would this be a straight transmission swap or are the front and rear diff non-conpatable?
Also, anyone ever experienced the "stuck in a gear" problem?

[ARCHINSTL]

Welcome to the Club!

The ratios are different in '83-4 and '85-8. See https://tercel4wd.com/forums/viewtopic.php?f=2&t=930.
I believe some peeps have a later rear end - but depending on the distance, you'd be better off scouring salvage yards.
Tom M.

[romarvi]

I read in a previous thread that you could swap an 83 for a 87 trans provided you swap out the front diff, wouldn't that hold true the other way around ? A 87 trans for an 83/84?
https://tercel4wd.com/forums/viewtopic.php? ... 148#p54623

[ARCHINSTL]

Yup - I figgered you'd be installing the '87 diff along with the trans; all is good if you stay with compatible diffs.
Tom M.

[Petros]

swapping out the trans and diff would be a good way to use the later trans, the later 4.1:1 ratio is better for this car anyway. You install a new clutch and rear main seal while you are there. If you are getting the whole '87, you might consider swapping the motor out of the ''84 into the '87, depending on which one is in better shape. Also, the composite headlights on the '97 are worth swapping over to the '84, they are much brighter than the old sealed beams.

Of course both cars might be worth fixing, good clean bodies are becoming more rare, engines are easy to find, trans less so, but a trans replacement, or engine replacement is much easier and faster than fixing a lot of dents, rust and a new paint job.

good luck.

[romarvi]

Gonna stick with the 84, straight rust free body, everything electrical works, no tears or stains in the upholstery, door and window seals all good. Got the window cracks to work like new again.
So the plan is to swap the trans and diff, the guy thats helping with the swap is a toyota mechanic and owed of the 87. Get to use the toyota dealership shop this weekend for the job. One thing I'm not sure of however (again, new to these cars), the transmission and front diff, what about the rear diff, shouldn't it get swapped as well? And whats a good clutch pack to put in, theres a number of them out there to choose from.

[Petros]

I think you misunderstood; if you put in a new front trasnaxle assembly that includes the front diff, you MUST also swap out the rear diff so both the front and rear diff ratios are the same. The front diff comes off with the trans as a unit (the FSM shows you separating the trans from the bellhousing/front diff assembly, do not do it that way, way too much work, pull them together as a unit). You can drive it with them miss matched but you MUST NOT USE THE 4wd feature or you will badly damage the new trans, the rear diff or both.

The rear diff is a relativity easy change: drain it, pull the drive shaft, pull the rear axles out about 5-6" inches on each side so the inside ends clear the diff assembly (hang the axles so you do not damage the axle seals inside the housing, do not let them rest in the axle housing it will damage the seal). than you unbolt the third member, six or eight 12mm nuts if I remember correctly, and than pull the whole third member assembly out. DO NOT SEPARATE the ring and pinion from the third member assembly, but swap out the whole assembly as a unit. Use form-a-gasket or a new diff gasket, remember to refill the diff with gear lube (as well as the trans assembly!) when you are done.

[romarvi]

Swap update: no swap. After discussing this project with the local Toyota guy, he was afraid that once we tore into it, we may encounter other things that may not match to the difference in model years. I found an 84 trans and its being shipped to me as I type. I really wanted to keep it original and besides, now the inclinometer will still work with the new tranny. Should arrive late next week and possibly have it driving by the end of the weekend.

[Petros]

everything swap over just fine, I have done it. you at most may have to change out one of the connectors to make the "4wd" on the incliometer work properly, but you do not need that to drive it. The later trans also has an extra low gear indicator that the early ones do not (a little "EL" light comes on the dash, as if you needed a warning about it), but that is just an electrical connector that will go unused in the '84 since there is no "EL" indicator light on the dash.

You can slap the trans in one weekend, not connect anything else, and drive it for a week (not using the 4wd at all), and than slap in the match rear diff the following week. and than mess with the wiring later. There are only two connectors you need, the back up light (should be the same in both) and the 4wd indicator light (which might need to swap over the connector if not the same). But you can drive it without either of these connectors working.

[romarvi]

Anyone up for helping a newbie swap an 84 trans in the Olympia area? Have access to a lift which makes it nice.

[dlb]

no disrespect to your toyota buddy but he need not worry about unexpected mismatches, romarvi. as petros and achinstl mentioned, there is no issue in swapping transaxles as long as the matching rear diff goes with it. many on this forum have done it so we know this. it doesn't matter since you're going a different route now but it's good to know for future reference, anyway. i personally prefer the older 3.73 trans ratio so i'm pleased you're sticking with it.

i also wanted to mention that the inclinometer will illuminate correctly regardless of which trans it is mated with. i believe it would even work correctly in an automatic, though i haven't tried that myself...yet.

good luck with your swap!

[romarvi]

Okay, here is a basic question,
What is a good brand and weight of gearbox oil? Is there one of high mileage like they have for engines or just a good brand 90 weight?
Also, what is the capacity of the the trans, and differentials?

[dlb]

if you have the little owner's manuals, those have all of this info. if not, download the factory service manual from here, as it has much more info than you will ever need and is an excellent resource:

https://tercel4wd.com/forums/viewtopic.php?f=2&t=8103

the transaxle takes 4.1 liters of gear oil. i can't remember how much the rear diff takes but it's not much, and it's in the manual anyway. i've used generic traditional 80w90 gear oil and it's worked well. some people use synthetic, or a mix of both. there is lots to consider and everyone has an opinion on this so take it all in and make your own decision, and if you're unsure you can just stick with what toyota recommends. here's a thread discussing traditional vs synthetic gear oil:

https://tercel4wd.com/forums/viewtopic.php?f=2&t=8271

[romarvi]

Done, success. Shifts like butter. Not very hard at all. Had the Old tranny out and the new one in in about three hours. Too bad I'm giving this one my daughter, I would like to keep it for my daily driver.