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Discussion Starter · #1 ·
so i been reading about how you cant change the gear ratio in the rear if your going to use 4x4, i know that, but then i got worried, cause when i got my bronco it had the transfer case gutted and i just rebuilt it

i tested it out abit but not super hard and nothing bad happened and it works but it was on dirt and gravel, is there a good way to test if the previous owner didnt change the back ratio?
thanks
 

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Get on flat asphalt or cement. Stop. Lock it in and release the brake SLOWLY. If truck moves without throttle, then all should be good. If truck doesn't move, take out of 4wd and assess further. Do not attempt to give throttle at this point.
 

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1987 Bronco 351W, C6
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You could put it on a lift, mark the tires, put in in 4WD and see if they spin the same speed. Wish it was easier to pull the cover on a D44, then you could just count teeth....
 

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You can change gear ratios, but you have to change BOTH front and rear. You won't get an exact match on the front, but you'll get close enough to make little difference when you need it.

In any case, you shouldn't use 4WD on dry, bare pavement. Even with stock gearing, the front wheels will turn at slightly different speeds than rear. You only want to use it when the road or driving surface is slippery.
 

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Discussion Starter · #6 ·
Get on flat asphalt or cement. Stop. Lock it in and release the brake SLOWLY. If truck moves without throttle, then all should be good. If truck doesn't move, take out of 4wd and assess further. Do not attempt to give throttle at this point.
ill try this
 

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Discussion Starter · #7 ·
Get on flat asphalt or cement. Stop. Lock it in and release the brake SLOWLY. If truck moves without throttle, then all should be good. If truck doesn't move, take out of 4wd and assess further. Do not attempt to give throttle at this point.
yup !!! just tested it and the truck moves with out any throttle input
 

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Driving Stuff Henry Built
-90 xlt, 351w, e4od, man 1356, 3.55, sag, warn hubs, 35s. -73, 400, np435, d20j twin, 35s
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Just to be sure, did you lock the front hubs?

I test drove a Bronco with mismatched front & rear gears. That was a wild ride for a very few feet. It was bucking & lurching. Once stopped I had a hard time getting out of 4 high. I took it back to the seller, who told me that "it should normally be used in 4wd with the front hubs unlocked, unless you're in slippery mud or sand". 4wd with hubs unlocked!? That's called 2wd. I passed.
 

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1986 Eddie Bauer 5.0EFI AOD Full length headers Y pipe into single 3" Magnaflow 3" factory exit
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Yeah 4x4 means you have a front differential and a rear differential... so if you change the rear, you have to change the front too... so double the cost, and then some...

I just had my Corvette rear diff changed last fall from a 4:11 posi, back to its original 3:70 posi, and even with me removing it from the vehicle & bringing it in on a roller cart so it was as easy as possible for them... it still cost $1000 to swap gears & change out all 3 seals on the independent rear diff it has.
181588


On a Bronco its probably more than that per axle, as the axle shafts need to come out to change gears & that means all of the brakes have to come off, including backing plates, on the rear.. On the front axle its even worse with TTB, hubs, brakes, axle shafts, ect... then which parts are bad, and what parts don't come apart easily..you'll be paying out the wazoo for lots of hours in labor for this. I'd guesstimate probably $2500-$3,000 for this.

Then when your done. Your big heavy 5000lb Bronco will feel just slightly less slow, and be worse on gas with higher rpms on the freeway.

The juice is just not worth the squeeze...

I don't mean to always be Debbie downer on these questions, but this is the reality of things & why I've learned to enjoy them as stock vehicles, cuz $10,000 in modifications later, its still a big heavy Bronco that can't beat a rusted out 1996 grand am off the line, but it is your money to spend as you see fit.
 

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Yeah 4x4 means you have a front differential and a rear differential... so if you change the rear, you have to change the front too... so double the cost, and then some...

I just had my Corvette rear diff changed last fall from a 4:11 posi, back to its original 3:70 posi, and even with me removing it from the vehicle & bringing it in on a roller cart so it was as easy as possible for them... it still cost $1000 to swap gears & change out all 3 seals on the independent rear diff it has. View attachment 181588

On a Bronco its probably more than that per axle, as the axle shafts need to come out to change gears & that means all of the brakes have to come off, including backing plates, on the rear.. On the front axle its even worse with TTB, hubs, brakes, axle shafts, ect... then which parts are bad, and what parts don't come apart easily..you'll be paying out the wazoo for lots of hours in labor for this. I'd guesstimate probably $2500-$3,000 for this.

Then when your done. Your big heavy 5000lb Bronco will feel just slightly less slow, and be worse on gas with higher rpms on the freeway.

The juice is just not worth the squeeze...

I don't mean to always be Debbie downer on these questions, but this is the reality of things & why I've learned to enjoy them as stock vehicles, cuz $10,000 in modifications later, its still a big heavy Bronco that can't beat a rusted out 1996 grand am off the line, but it is your money to spend as you see fit.
Not if you use that 10k to do a coyote/6r80 on it ;)


Sent from my iPhone using Tapatalk
 

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Addicted to Junk
85 Bronco, 309ci I6 w/4bbl, np435, 4" lift, 37" Irok NDs, 4.56 w/ Detroit Locker and tru trac
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I just had my Corvette rear diff changed last fall from a 4:11 posi, back to its original 3:70 posi, and even with me removing it from the vehicle & bringing it in on a roller cart so it was as easy as possible for them... it still cost $1000 to swap gears & change out all 3 seals on the independent rear diff it has
I know its a vette, but thats a lot for a gear change!
 

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I know its a vette, but thats a lot for a gear change!
I had a chevelle done at another place, from.a 3:23 open to a 3:73 posi and it was about $900 so I felt like it was reasonable price. Maybe the detroit area is a bit more expensive, there is a big classic car market around here?

When I blew up the rear end in my old escalde, that was a little over $1000... that is why I just lease new stuff now, I don't mind spending money on old cars, but i hated spending money on my newer cars/trucks hat I'd drive the wheels off of. I prefer to just get a new one every 2 years.
 

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85 Bronco, 309ci I6 w/4bbl, np435, 4" lift, 37" Irok NDs, 4.56 w/ Detroit Locker and tru trac
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If thats them buying all the parts, thats reasonable.
 

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If thats them buying all the parts, thats reasonable.
Yes that is just me making a phone call, dropping it off, & picking it up when finished... jobs like this are above my level of hack!

The guys that lift thier trucks, spend all that cash on the lift, then tires & rims, then gear ratios, it adds up real fast how much you spend & none of that stuff makes the truck worth a penny more.

As far as making sure your front & rear ratios match, if.you can get.the truck on a 4 post or up on 4 jack stands you could mark all 4 tires with tape & let them rotate slowly in gear and see.how they compare after a few rotations. Maybe have someone in the truck riding the brakes to slowly rotate the tires, but who knows how well that would work with a non posi front/rear pig?
 

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1989 Eddie Bauer 5.8, C6, True Trac diffs, 4.56 gears, 4" C&T lift, 130A 3G Alt, 35" Grabber AT2s
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Front D44 doesn't require entire axle to go to shop. Can be pulled and upgraded/downgraded/changed without truck or axle. Rear is a different story
 

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Changing gears makes a huge difference in drive-ability once you increase the tire size. For me the juice is worth the squeeze because I don't plan to ever sell. To each his own.
 

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Yeah, $1,000 doesn't sound bad for a gear change. I recently had my son's '69 Mustang SportsRoof changed from a 3.73 to a 3.25 and IIRC it cost around that for the gear swap. With it's 351W and 3 speed FMX transmission it was nearly undriveable on the highway with the 3.73's. He and I had installed them to replace the stock 9" 2.69 peg leg that was in the car when he bought it. I had advised him against the low gears but everybody has to learn.
 

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Yesterday I went to local diff shop to inquire about taking my 3.55 ratio to a 4.11 in my FSB.
They ball parked it at $2500-3000 for both axles and ALL of the parts and labor. (plus anything else I want to address like spider gears, axle bearings etc)
Gear ratio changes do make things a little better but it doesn't totally make up for a low power engine.
 

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If I was rolling on stock size tires I wouldn't swap gears but if I was adding larger tires I would definitely want lower gears.
 
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