Part time fzj80 transfercase

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Oct 27, 2003
I've been working on making my 94 FZJ80 transfer case part time. To finish the project I would like to find a viscous coupler that is no longer working/burnt...I plan to make a solid splined coller to take the place of the coupler but I need one to pull the dimensions from. Sooo, if anyone has one lying around that hasn't made it into the trash bin, let me know I could use it. Thanks! :cheers: I'm located in southern California.
Kurt's got at least one. (Landtoy80).

He be in WisCOWsin :rolleyes:
Far out! :D Is he interested in parting with one?

Maybe.... you'll have to ask him. Don't tell him I said so, but chances are... it leaks. :D
Actually a leaking one would be perfect. It would be better if it was already trashed. Thanks for the heads up.

29Oct2003 (UTC -7)

Dude, call Marlin of . He has one burnt tranny(?) & t-case in his yard, he maybe willing to make a deal. I saw it buried down there in Fresno. :banana:
Thanks for the heads up. I'll give Marlin a ring.

As far as I can tell you don't need the VC in the t-case. I tested the old t-case without the vc (off the vehicle) and it worked like a non vc t-case. It just slips on the rear output shaft. I was going to just remove it but I wasn't sure if it balanced or put pressure on a bearing. Also the t-case was getting hot so I think it was a bad bearing/s. My VC might be just fine for all I know.
Not to rain on your parade but I will do it any way ;)
There are several problems with a part time system;
1) the t-case is actually a differential, it would be like trying to get your rear diff to send power to only one wheel.
2) by adding lockouts, your front drive line will still be truning

This is the center diff with VC. Note the teeth on the center diff, the vc has teeth and they slide together. If you replace the VC with a spacer, you will be rubbing metal to metal there.

One thing you could do is weld the VC so it kan't spin. Then you will always have power to the rear.
The VC has two sets of teeth. One set of teeth grab on the center diff, other teeth are on the rear output shaft.
This is without the VC
The VC is 11 lbs. Removing it might cause a balancing problem but I doubt it.
With the VC off power will go the diff with the least resistance. If the front end if off the ground, you will be stuck. Same with the rear.
Thanks for the input and excellent pictures. Actually though, I do understand the operation of the t-case, center diff. and viscous coupler. If you look at the power flow between the coupler and the center diff 'carrier' what you find is that if the coupler is locked or replaced with a solid coupling coller, then the rear output shaft is locked to the input through the carrier. Power flow then goes directly from the gear through the carrier and to the rear output shaft. Once this is accomplished, the splinned portion of the front output shaft can be machined off so that is no longer part of the center diff drive system. With the installation of the factory center diff. lock button, you now have control of coupling and decoupling the front drive. This behaves just like the '4wd' button on an FJ62. The addition of front locking hubs completes the set-up and have a part time system. Soooo, the reason for finding a unwanted viscous coupler is to use it for reverse engineering a solid splined collar to take it's place. Actually I could pull mine out but I was trying to avoid down time as my 80 pulls a lot of family transport duty during the week. To date, I have installed front Aisin hubs and the center lock button. As a test I have been driving around for the last month with the front drive shaft out and the center diff. lock engaged. The results have been slightly improved fuel economy (most noticable when towing my FJ40) and lighter more responsive steering. The long term benefit is less wear and tear on the front drive and I won't have to do inner axle seal replacements as often. Yeah! Sorry about the long winded reply...I hope I made sense,

If you eliminate full-time AWD you'll have to start rotating your tires ;)
I'm sure you've thought this through but maybe there's still time to get you thinking about this.

In my opinion and others that know the 80's very well, you are disabling one of the most elegant FT 4wd systems in the world. It works very well and is one of the strengths of the 80 series.

You've only seen a slight improvement in fuel economy and many would suggest you won't see any substantial improvement after you complete the mods. You will never cover the cost of this modification with lower fuel costs. The axle seals cost about $10 and it takes a weekend out of your life every 5 years or so. Big deal. Well maintained 80 series front axles will not wear out; at least not in your lifetime, so the wear and tear argument is lame.

Sure, you can do it... others have. But why would you want to???? (Rhetorical question, no response necessary.)

One thing you should do before doing anything. Remove the front driveshaft and drive it.
When shifting into D or R all of your tork will be at the rear wheels. On mine, the tork on the rear suspension would raise the vehicle up in D and in R it would lower (or vise versa as I don't remember). With the front drive shaft on it balances out.
One other thing that happened ( maybe it is only on mine) when I floored it from a stop, the very slight hesitation I have was more noticable.
Excellent points! Actually I have driven it for over a month with the front drive shaft removed. The driving has included towing, highway and around town. Although I have only charted about a 2 mile per gallon fuel economy improvement, the overall drivability is better. About those seals...with all of the cruisers hanging about the house, I'm happy to avoid as many inner axle seal replacements as I can :). As to why...ah heck, besides the drivability and stuff, it's a challenge and there is a bit of cool factor in having functional locking hubs on the front. Besides, when I was in the Middle East I happened across a factory 80 series with part time four-wheel-drive and a 5-speed and it got me thinking. So far half of the fun has been thinking through the challange...anyway thanks for all of the input.

I personally like it. And if you are seeing a 2mpg increase I would say that it would be worth it. Good luck and keep us informed. I too like part-times very much.
Now to find lockouts. When I got Newfields the shaft that goes to the flange was shorter than the 94 birfield so I had to get new flanges so I could put the snap ring on. What vehicle would you get the lockouts from?

That's a pretty interesting mod, and will take some slick machining. Go to it, and share your results, eh?

One variable worth noting is that I believe one function of the coupling was to that it made the 80 the first full time 4WD with ABS at a time when other vehicles had to have their ABS systems shut off when shifted into 4WD. Making a mechanical coupling there may have some impact on the functioning of the ABS. The rears will certainly be more prone to lockup in 2WD since you've doubled the engine's braking torque to them. Ironically, I've always felt the 80's brakes were too front biased (adjusted my proportioning valve long ago as a result), and this may actually help prevent premature front lockup. Hmm, I'll have to think about that. Minor issue, but some input for you.

Good luck in this project, and keep us posted.


PS - can a RWD 80 burn rubber if provoked? Post a pic of an 80 doing a powerbrake burnout and you'll be my hero :p
ABS. That is one thing you might have to deal with.
WHen I was going to just remove the VC and go drive without it, I was thinking I would need to disable the ABS.
In 2WD you might be able to keep ABS but not sure what will happen when in 4WD.
If you don't drive in snow/ice this shouldn't be a problem.

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