From what I've read, I can't really tell the difference between ADD hubs and manual hubs that are always locked. With ADD the drivetrain is always spinning, isn't that the same as manual hubs that are in the locked position?

 

ADD trucks are equipped with flanges.... Check out this thread, it might help:

https://www.yotatech.com/forums/f31/add-flanges-sfa-1st-gen-ifs-70868/

Basically a flange acts as a solid connection between the CV shaft and a wheel, opposed to a selectable connection like a hub.

 

Yes, the add flanges are like a locked hub. However, with a hub, you can unlock it to keep the drivetrain from moving.

 

damn so those "add hubs" are kind of misrepresented if you ask me, i mean they arent really autolocking at all, theyre just always locked

 

you got it

 

The ADD is autolocking.

 

There's a little more to it than that, but first I'd like to commend GradSR5 on searching and asking an intelligent question. Bravo!!

In addition to the drive flanges, the other components in the ADD system include an actuator on the long side of the front diff assembly that uses vacuum to disconnect the axle shaft from the diff. The rigs that came with manual hubs from the factory, don't have this actuator and all the related stuff, so they are a simpler more reliable system (by fewer parts). When I regeared, I just used an older non-ADD style front pig so I eliminated all the ADD stuff on mine with no ill-effects. I had replaced the flanges with manual hubs previously.

And no, ADD is not Autolocking. That is something different completely.

 

Take a look at one.

There are NO moving pieces, locking parts or ANYTHING LIKE THAT in an ADD drive flange.

 

no, ADD ARE LOCKED by definition. since the flange connects the hub to the axleshaft.

toyota did come out with auto locking hubs. and from all reports i read, they would unlock at the worse moment...

ADD is not even part of the hubs. or visa versa.

it's the machanism that connects the driver's axleshaft to the differential.

ADD=auto disconnecting differential...

 

Your best bet is to convert to manual hubs. Use the search it has been done many times. It would probably save you a couple of dollars in gas too. Manual hubs are easy to rebuild and put less strain on the front drive system. If you are super lazy then stick with the Auto/ADD

James

 

Just read my post again. I said the ADD is auto locking. I never mentioned the hubs/flanges. The AUTOmatic Disconnecting Differential sleeve connects the axle automatically when you shift into 4wd.

 

worse than the ADD is the AUTO hubs. They were on my 4runner for all its life up until about 1 1/2 years ago. Its fun goin through mud with 4wd engaged and wondering why you're stuck. Def. go with manual hubs if you plan on changing. My best investment yet.

 

Actually, I didnt ask the question.

 

Oops! Sorry about that - fixed my post.

 

no worries

 

Sounds like some folks don't understand the 3 systems. (Three mentioned in this thread - there is also AWD - but lets leave that to the soccer moms...)

Manual hubs: When 4wd is engaged the front driveshaft drives the front diff and the front axle shafts turn. You manually engage and disengage the hubs by turning the lock ring on the hub by hand. Simplest and most reliable.

Auto hubs: When 4wd is engaged the front driveshaft drives the front diff and the front axle shafts turn. The axle torque to the cam mechanism inside the hubs themselves causes the hubs to engage to get the wheels to drive. To disengage it you put the transfer case back in 2wd and back up to get the hubs to disengage themselves. Note that in 4wd when you back up they must disengage then re-engage the other way - slamming back and forth (rocking) while stuck is a sure way to explode an auto hub. They are still quite simple but very weak and notoriously unreliable.

ADD: There are no 'hub' mechanisms. The "hub" is just a solid steel flange - so the axle shafts turn all the time with the tires. Instead, the front end engages into 4wd with the ADD mechanism - a vacuum operated axle disconnect which consists of a sliding splined sleeve on one front drive axle. In 2wd one drive axle is disconnected, owing to the action of the differential this 'unlocks' the front end. To engage 4wd, when the tcase is put in 4wd, vacuum is sent to the ADD mechanism, engaging the disconnected axle and now the front end works normally. To disengage, shift back into 2wd and vacuum will unlock that one axle allowing the front end to be non-driving again. The system is very strong and reliable - it's used in some form on nearly every 4wd made today. Once you get up to 35"+ tires and very severe 4wheeling you may find the strength limit. 99% of us could never break it. The vacuum switching valves and wiring are the only thing that are likely to need repair in time, but they are simple. Contrary to common conception, this system does not cost measureable fuel economy - the disconnected parts have so little resistance it makes no real difference.

 

What Flamedx4 said..

And.. I put manual hubs & locked the diff slider to engaged with a hose clamp on my '90.. worked like a manual system, trouble free after that..

Worked so well, I shoulda done it in '93 when I bought it.. would do my '96 if it had mounting holes on the stock hups.. whole nuther story..

 

I suppose technically you could keep the ADD and have manual hubs also.

 

You bet. LOtsa people (including me) have done that. Best of both, you can lock the hubs beforehand and shift on the fly (nice in winter) or unlock for your day to day driving.

 

But you didn't notice any gas mileage improvement?