Front Diff (posi) Locking Question

[Aegis43]

I apologize for being a newb/rookie. I'm sure there are many posts on this question here, but not finding any with key words I would use. I have a 1988 K5 with factory 10-bolts front and rear. As best as I can articulate here goes: In 2WD High, with Warn manual locking hubs in the unlocked position, if I had a posi (I get it guys who hate that term) or other limited slip type differential, would I experience torque steer? Or any other negative experience, especially on the street/highway?

Thanks. I really do appreciate your guys' experience.

 

[sweetk30]

2wd is rear axle only . If factory posi its a gov-lok and weak and brakes easy .

No factory posi in front axle were offered unless k30 1ton truck and specific 2 a few military only units .

Torque steer is a thing but not near as much in your setup factory .

Hope this clears it all up .

 

[Cucv_M1008]

Spartan locker.

 

[tarussell]

To answer your direct question about if you would experience any kind of issues related to any kind of L/S up front the answer is no - under the circumstances you described being in 2WD and with the hubs unlocked.

Depending on what type of L/S being used you will have a little trouble locking and unlocking the front hubs due to the resistance of the side gears ability to move and not allowing the axles to rotate freely like an open differential would.

The OEM or WARN ( same parts ) hubs will work much easier than other types due to the design - the dial can turn even if the axles are binding on the hubs internals and lock/unlock once the friction allows.

Hope this answers your question.

Tom

 

[Aegis43]

2wd is rear axle only . If factory posi its a gov-lok and weak and brakes easy .

No factory posi in front axle were offered unless k30 1ton truck and specific 2 a few military only units .

Torque steer is a thing but not near as much in your setup factory .

Hope this clears it all up .

It doesn't really. The Blazer has open diffs front and rear right now. My question is if the front hubs are in unlocked position, and the truck's transfer case is in the 2H position, would I "feel" anything as a result of having a posi in the front vs an open diff?

Only forum members who have run both scenarios would know the answer to this question. They are who I am directing this question.

 

[Aegis43]

To answer your direct question about if you would experience any kind of issues related to any kind of L/S up front the answer is no - under the circumstances you described being in 2WD and with the hubs unlocked.

Depending on what type of L/S being used you will have a little trouble locking and unlocking the front hubs due to the resistance of the side gears ability to move and not allowing the axles to rotate freely like an open differential would.

The OEM or WARN ( same parts ) hubs will work much easier than other types due to the design - the dial can turn even if the axles are binding on the hubs internals and lock/unlock once the friction allows.

Hope this answers your question.

Tom

Yes, that is the answer I am hoping for, even if it was not what I am looking for. Although it is. I assume you mean to imply that when after I lock in 4wd, and then want to go back to 2wd, I need to be very mindful/careful to ensure I unload the front diff by shifting back to 2wd, returning hubs to unlock position, then driving the truck in reverse while turning the steering wheel back and forth and hitting the brakes multiple times under load.

 

[tarussell]

Just curious - what type of front diff are ya thinking about using ?

 

[Aegis43]

Just curious - what type of front diff are ya thinking about using ?

Looking for suggestions. I am not hardcore. No rock crawling. I am just weird about having four-wheel drive. Not three-wheel drive, not two-wheel drive (one rear wheel and one front wheel). My plan for the rear is an Eaton-type differential.

 

[tarussell]

The reverse method was so that GM’s auto locking hubs could relax and unlock.
You’ve got the right train of thought by understanding going backwards or forwards to allow the axles to “relax” and slight turning of the wheels while rolling helps.
This scenario has different results depending on what type of L/S and style of hubs are being used.

 

[tarussell]

Looking for suggestions. I am not hardcore. No rock crawling. I am just weird about having four-wheel drive. Not three-wheel drive, not two-wheel drive (one rear wheel and one front wheel). My plan for the rear is an Eaton-type differential.

Sounds good!

A true four wheel drive is a nice thing to have but there are times where a front L/S diff is a pain in the backside - such as snow/ice conditions.

EATON now offers several different types of “L/S” diffs so narrowing it down to which one will be necessary.

Any thoughts on which type of EATON ?

 

[Aegis43]

The reverse method was so that GM’s auto locking hubs could relax and unlock.
You’ve got the right train of thought by understanding going backwards or forwards to allow the axles to “relax” and slight turning of the wheels while rolling helps.
This scenario has different results depending on what type of L/S and style of hubs are being used.

Do you have a recommendation? Let's put it this way, if I was on the street in 4wd and wanted to do a four wheel burn out (I'm not going to do that), what differential unit would you advise?

 

[Aegis43]

Sounds good!

A true four wheel drive is a nice thing to have but there are times where a front L/S diff is a pain in the backside - such as snow/ice conditions.

EATON now offers several different types of “L/S” diffs so narrowing it down to which one will be necessary.

Any thoughts on which type of EATON ?

Well that's a conditional situation. My plan is to relocate to places where snow and ice "can" happen. Kentucky, TN and North Carolina are all under consideration. Snow/ice are very occasional, I get that.

 

[tarussell]

Do you have a recommendation? Let's put it this way, if I was on the street in 4wd and wanted to do a four wheel burn out (I'm not going to do that), what differential unit would you advise?

A very nice mild and fairly strong front diff choice could be an EATON True-Trac.
They have great manners and are fairly easy on the axles ( front 10B axles ain’t the strongest…) and great drivability.

There are various bias ratios and since it will be used up front the internals need to be reversed to be effective going forward.

 

[Aegis43]

A very nice mild and fairly strong front diff choice could be an EATON True-Trac.
They have great manners and are fairly easy on the axles ( front 10B axles ain’t the strongest…) and great drivability.

There are various bias ratios and since it will be used up front the internals need to be reversed to be effective going forward.

I appreciate that. I assume having a True-Trac in both front and rear would be a good choice for my application.

Thanks man,

 

[tarussell]

I appreciate that. I assume having a True-Trac in both front and rear would be a good choice for my application.

Thanks man,

They are a very effective and don’t fight ya while driving in various types of conditions.
From what you described a T/T would be a good choice for both diffs of your ride.

 

[sweetk30]

It doesn't really. The Blazer has open diffs front and rear right now. My question is if the front hubs are in unlocked position, and the truck's transfer case is in the 2H position, would I "feel" anything as a result of having a posi in the front vs an open diff?

Only forum members who have run both scenarios would know the answer to this question. They are who I am directing this question.

If you have a wheel joint binding up from rust and wearing out it can act funny when turning . Otherwise hubs in UNLOCK and 2wd tcase there is ZERO way for it to bind up in that combo .

 

[ZooMad75]

A very nice mild and fairly strong front diff choice could be an EATON True-Trac.
They have great manners and are fairly easy on the axles ( front 10B axles ain’t the strongest…) and great drivability.

There are various bias ratios and since it will be used up front the internals need to be reversed to be effective going forward.

I’ll throw another vote in for the Eaton tru-trac up front. 2wd hubs unlocked and you don’t know it’s in there. The tru-trac has been awesome for me off road, dirt, rocks or snow.

The only time I’ve run into any odd handling was coming back from a snow run in the mountains. On the road coming home there was patches of snow and dry pavement. At speed I hit a patch of snow with one tire while the other was on dry road and it torque steered to the side with traction. It was actually pretty startling the first couple of times it did it. I wised up quick and shoved the t-case back into 2hi.

One time out of countless snow runs would not make me want to swap it for anything else. If the road is completely snow covered it’s never done it. Same if it’s dry. But that day taught me quick to take it out of 4hi if the road is patchy with snow.

 

[Blue85]

My question is if the front hubs are in unlocked position, and the truck's transfer case is in the 2H position, would I "feel" anything as a result of having a posi in the front vs an open diff?

Only forum members who have run both scenarios would know the answer to this question. They are who I am directing this question.

If the hubs are unlocked and the T-case is in 2WD, it doesn't matter what differential you have up front or even what gear ratio. Everything is free-wheeling.

If you're really going down the rabbit hole, it will be mentioned that the front driveshaft does sometimes turn a bit when you're in 2WD/unlocked hubs, but no appreciable torque can be transferred, so nothing bad is going to happen.

I think the interesting part of the discussion is what happens with various types of front differentials when in 2WD but hubs locked.

 

[Conner]

Does your '88 have 28 or 30 spline axle shafts? Maybe someone can correct me if I'm wrong, but the Truetrac is offered in front application (#912A557) and rear application (#912A556) for 28 spline, but only rear application (#913A481) for 30 spline.

So if 28 spline you can just buy a front and a rear, but if 30 spline you would need to buy 2 rears and "flip the gears" in the one going in the front.

I found this guide for flipping the gears in a Truetrac to convert from a rear application to a front application, or vice versa. To my understanding this just puts the primary wear/load on the differential case when the differential "locks" (using that word loosely), as opposed to the side gear. It works either way and apparently the bias ratio is the same either way (so the differential works in reverse too), but it just puts the load in a more desirable place for the majority of its function (in drive vs reverse). Supposedly the only difference between a front and rear application Truetrac is the orientation of the gears.

I also think you may need different bearings than normal with the Truetrac for the GM 8.5"/10 bolt axles (see the "Catalog Notes" section on the above-linked Eaton web pages).

Disclaimer: I have not done any of this myself (yet, at least), but hopefully this information is helpful.

 

[tarussell]

Does your '88 have 28 or 30 spline axle shafts? Maybe someone can correct me if I'm wrong, but the Truetrac is offered in front application (#912A557) and rear application (#912A556) for 28 spline, but only rear application (#913A481) for 30 spline.

So if 28 spline you can just buy a front and a rear, but if 30 spline you would need to buy 2 rears and "flip the gears" in the one going in the front.

I found this guide for flipping the gears in a Truetrac to convert from a rear application to a front application, or vice versa. To my understanding this just puts the primary wear/load on the differential case when the differential "locks" (using that word loosely), as opposed to the side gear. It works either way and apparently the bias ratio is the same either way (so the differential works in reverse too), but it just puts the load in a more desirable place for the majority of its function (in drive vs reverse). Supposedly the only difference between a front and rear application Truetrac is the orientation of the gears.

I also think you may need different bearings than normal with the Truetrac for the GM 8.5"/10 bolt axles (see the "Catalog Notes" section on the above-linked Eaton web pages).

Disclaimer: I have not done any of this myself (yet, at least), but hopefully this information is helpful.

If I’m not mistaken the notation for the bearing difference is because the carrier journal size difference between the 28 & 30 spline cases.
The 30-spline carrier bearing journals are larger ( making room for the slightly larger axles ) and therefore the inner diameter of the carrier bearings is larger than the 28-spline versions - but that means the 30-spline versions have smaller tapper rollers in the bearings to compensate for the size difference.

Many of the OEM carriers broke right at the thrust side journal on the 30-spline units - the fix was to strengthen the journal area a bit. The aftermarket L/S carriers never seemed to have any journal breakage issues.