Gears for Front Diff?

J

'JustDreamin'

Dream: 6LV8 Turbo Bravada
Hi Guys...

I've got the front diff from my '99 Bravada out, and man it feels and sounds terrible. When you spin it over, I don't think its supposed to click!

Anyway, I'm going to put the truck back together without the front diff or half shafts. I'm going to use some nice 24mm bolts (12.9 grade) and some custom washers to hold the spindle assembly together (since I don't want to take the halfshafts apart, they feel ok).


My question is: Who's the best source of gears for the front diff? I know its the puny little GM 7.25" IFS, and doubt places like Summit or Jegs will have gears for it. And there's no way I'm going to order them through the "stealership" if I can avoid it.

Any suggestions? Sources that you guys have used that had good prices, good product, and good customer service?

Thanks in advance.

'JustDreamin'
 
J

'JustDreamin'

Dream: 6LV8 Turbo Bravada
Re: Gears for Front Diff?

I've got 3.73's currently.

However, I'm planning on swapping to 3.42's. Between the 4L80E cutting some overdrive ratio out and having 100+ more horsepower & torque than the stock V6 (6.0L V8) I think it should run better & get better gas mileage with a little less gear.

So, I'm probably looking for a set of 3.42's. But let me know what you'd want for that set of 3.73's. I'm not sure that I'm interested, but....Also, aren't you still out "playing in the sand"?

'JustDreamin'
 
Robert Lone

Robert Lone

MUTANT
Re: Gears for Front Diff?

Still in the sand but not for long...:tup:

I'm going to 4.11's to make my .62:1 OOD usable.
 
J

'JustDreamin'

Dream: 6LV8 Turbo Bravada
Re: Gears for Front Diff?

T-56 said:
Still in the sand but not for long...:tup:.
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Glad to hear you're getting out of the sandbox! I'm sure it can't be soon enough.

T-56 said:
I'm going to 4.11's to make my .62:1 OOD usable.
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What size tires are you running? What rpm are you turning at cruise speed?
My Z28 has the same OD ratio ('93 T56) and same rear gears (3.73's) and turns reasonable rpm in 6th (I think it turns about 2000 at 70) with 275/40/17's. Then again, its got V8 torque at that speed.

Just curious...

'JustDreamin'
 
Robert Lone

Robert Lone

MUTANT
Re: Gears for Front Diff?

My DRAC is still calibrated for the 3.42's and I haven't done the math. I do know that if the speedo is indicating less than 100, 6th is useless.:tdown:
 
J

'JustDreamin'

Dream: 6LV8 Turbo Bravada
Re: Gears for Front Diff?

If you give me the tire size, I'll run the calcs for you. Just the tire size (275/40/17 or whatever) and what speeds you'd like rpm at (55mph, 100, any speed you'd like).

Or, if you're interested, I've got an Excel spreadsheet that I set up to compare the 4L60E and 4L80E's with various rear gear ratios and tire diameters. You'd need to modify it to reflect the T56 ratios, but I'm sure you could handle that. Let me know (PM me with an email address you'd like me to use) and I'll email it to you.
 
J

'JustDreamin'

Dream: 6LV8 Turbo Bravada
JSM

JSM

Active member
Re: Gears for Front Diff?

I know they have it, I just had my hands on some new gears for front diff for somebody. Very quick shipment also.
 
B

big gear head

axle builder
Re: Gears for Front Diff?

It might be easier to buy a complete assembly out of another truck. The 7.2 IFS is one of the most difficult differentials that I have built. It is very hard to check the backlash and bearing preload. The 3.42 was used in MANY 4X4 S series trucks, mostly with automatic transmissions. You should be able to buy a complete assembly for around $150.
 
J

'JustDreamin'

Dream: 6LV8 Turbo Bravada
Re: Gears for Front Diff?

If I buy a "new to me" diff, any suggestions as to how to get a good one? (Applications, warning signs, tips, whatever). Most of the salvage yards around here (Maryland and the mid Atlantic area) are way overpriced, so I'd probably be looking to do a mail order replacement.

I don't think a replacement Bravada one would be in any better shape unless it had very low mileage (which probably means $$$).

What application would you think would be in the best condition? Bravadas probably wear out the gearset (driving the front propshaft). I'd bet that 4x4's probably wear out the spiders / differential since they'd always be turning over.

How hard is it to swap spider gear sets?

Is the ProTrax locker (or whoever it was) still available?

Thanks....

'JustDreamin'
 
gkrcr882

gkrcr882

SyTyless......for now!
Re: Gears for Front Diff?

From what I heard, the Lok-Right front locker isn't that great for street use, especially in AWD applications. I think you're right in that the plain 4x4 front ends may have the least amount of wear (assuming the truck wasn't wheeled hard). One thing though: keep your axles from the Bravada, since the plain 4x4s use a two-piece on the long side to allow for disconnecting. (at least thats from what I understand).
 
B

big gear head

axle builder
Re: Gears for Front Diff?

You are correct, the 4X4 would have less wear. You are also correct about using the right axle from the Bravada. The 4X4 will have a yoke for a standard u joint. Your Bravada probably has a companion flange. They will have to be swapped too.
 
J

'JustDreamin'

Dream: 6LV8 Turbo Bravada
Re: Gears for Front Diff?

Actually, my '99 has a standard yoke, so I shouldn't have to change that. And I don't have a front propshaft yet anyway.


I've also thought about whether to run the Bravada Pass side axle or not.

The NV246 tcase that I'm running will tolerate running without a front shaft (its not a viscous box, its an active-on-demand box). So, I could make it selectable AWD, making it possible to drop out the front axle and maybe pick up a little MPG. I'm betting it'd be a small change since all that I'd not be spinning is the ring & pinion (under zero load) and the propshaft.

But is that change worthwhile? Do you think the change would be little?

Also, how big is the 4x4 axle tube, compared to the Bravada Pass tube? I'm not sure I've got oilpan clearance for anything much bigger than the Bravada tube with the oilpan I built.


Thanks for the advice on NOT trying to set up one of those 7.2" IFS's, Big Gear Head. I hadn't really thought all that hard about what I was going to get myself into. And thinking about it now, I don't know that I'm up for it.


Last set of questions: Assuming I pick up a salvage yard case with decent gears in it, should I pull it apart for inspection, cleaning, whatever? Should I put bearings in it? Or just clean the outside, change the two bolts that I have to (I have to change 2 bolts to socket flatheads for oil line clearance) and put it into the truck? Anything I should do to it (besides put decent fresh oil in it?).

'JustDreamin'
 
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B

big gear head

axle builder
Re: Gears for Front Diff?

The axle tube for the 4X4 is the same size as the Bravada tube. As for splitting the case, you don't have to do that to inspect it. There is a cov er on the left (driver's) side that you can remove to see the ring gear. You can inspect it that way without getting into the case. If you split the case you take the chance of upsetting the bearing preload. You should be able to feel a bad bearing by turning it. I would just remove the cover and see if there is any rust on the ring gear. If there is then it might have bad bearings too. The average 4X4 front end doesn't get rotated very often and often the side of the gear that is out of the oil will rust. Then the rust gets run through all of the bearings.
 
J

'JustDreamin'

Dream: 6LV8 Turbo Bravada
Re: Gears for Front Diff?

big gear head said:
The axle tube for the 4X4 is the same size as the Bravada tube. As for splitting the case, you don't have to do that to inspect it. There is a cov er on the left (driver's) side that you can remove to see the ring gear. You can inspect it that way without getting into the case. If you split the case you take the chance of upsetting the bearing preload. You should be able to feel a bad bearing by turning it. I would just remove the cover and see if there is any rust on the ring gear. If there is then it might have bad bearings too. The average 4X4 front end doesn't get rotated very often and often the side of the gear that is out of the oil will rust. Then the rust gets run through all of the bearings.
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Thanks for the thoughts on this BigGearHead.....

Now all I've got to do is decide what I'm going to do with the front diff. For now, I'm going to leave it and the half shafts out. I've got a pair of M24 bolts and some custom made retainer washers to hold the front hubs / knuckles together in place of the half shafts.


Last question: I've heard mixed reports about the Powertrax Locker, and haven't decided whether I'd want one or not, but had heard it has been discontinued. Anybody have confirmation of it being discontinued?

'JustDreamin'
 
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