3.55 open to 3.73 LS

[NHarris]

I currently have a 3.55 open diff in my 05 and I'm planning on doing a 1.5" lift with 30's or 31's. I figure I'll want to go with a 3.73 LS (locked rear eventually) some time in the future. Since I have a 4WD explorer I'll need to swap out both diffs, would it be easier and more cost efficient to just swap out just the gears or the whole unit itself?


I finally figured out why an open diff sucks. : I had little traction in the rear when I was doing some wheeling on a slope.

 

[gamecocks]

good question, i believe itd be alot easier to get the whole diff(s) and swap them but id also imagine itd be more costly... so just to be clear the 3.73LS equipped Xs came LS front and rear right?

 

[NHarris]

I think the front is an open.
I would probably go to the JY to get a unit (if there is a good shape 3.73) or I could just rig the 3.73's from my 2nd gen into my 3rd gen

 

[gamecocks]

eh oh well since im going to drop a lunchbox locker in (like ronin) im just going to eventually do 3.73s unless Ronins results from the 4.10s are outstanding!

 

[jd4242]

i would wait if you want to put a locker in down the road.most lockers use an open carrier and i would go 410 gears.no point in buying 3.73 open for the front when you can probably get just 4.10s for the same price.pm ronin he just did this

 

[jd4242]

eh oh well since im going to drop a lunchbox locker in (like ronin) im just going to eventually do 3.73s unless Ronins results from the 4.10s are outstanding!

haha beat me to ityes 3.55 to 3.73 you wouldn't notice anything,not worth it,4.10 would be ideal

 

[Glen4X4]

It would be easier to swap both diffs out because if you swap gears into a differential they still need setup and is done a lot easier outside the truck and you need some tools to do so. 4.10's would be more worth the swap.

EDIT: 31's with 3.55's is not that bad.

 

[gamecocks]

Ive talked to ronin im just waiting on his MPG results thanks guys

 

[NHarris]

It would be easier to swap both diffs out because if you swap gears into a differential they still need setup and is done a lot easier outside the truck and you need some tools to do so. 4.10's would be more worth the swap.

EDIT: 31's with 3.55's is not that bad.

You running 31's with a 3.55 diff on one of your exs?

 

[gamecocks]

i am and hardly notice a difference w/ the intake and exhuast, just sucks off road

 

[Glen4X4]

You running 31's with a 3.55 diff on one of your exs?

I was now I'm runnin 33's on it and that's the OHV and did great on 31's barely a difference and since you have SOHC you should be set, unless you go to 33's I really wouldn't worry about it.

 

[Ronin8002]

Here's a link to a calculator that lets you compare what your RPMs would be like with different gear ratio and tire sizes.

http://www.grimmjeeper.com/gears.html

It has the 5r55s/5r55w as options in the drop down. Choose manual or auto with lockup converter. For the transfer case just pick a BW1354 because they don't have ours and the ratio is the same as ours anyway. Select "no" for underdrive.

Based on what I can tell:

-Running 4.10's with 265/75/16 is almost the same as running 3.73's with 245/65/17 (stock tire size).

-Running 3.55's with a 31" tire is kind of like running stock (245/65) tires with a 3.38 ratio (I don't think such a thing exists, just an example though).

-Running 3.73's with a 31" tire is almost identical to running 245/65 tires with a 3.55 ratio.


General rule of thumb I have heard is that if you are going to go through the cost of re-gearing, might as well jump up 2 ratios (i.e., 3.55 to 4.10) to see enough difference. Now you can just swap in some junkyard 3.73's also and that would be cheaper. A lot depends on the tire size you plan on running. I just figured if I'm going to go through that work I might as well get an upgrade out of it instead of going back to essentially the stock gear ratio.

Also Nate, if you get a LS and you want to upgrade to a lunchbox locker later, there's always the Powertrax No-slip. It's a lunchbox that fits in a LS carrier and is supposed to be really smooth. Not sure how it would work in an IRS axle but it could probably be modified like the Aussie.

 

[The Electrician]

I'm not quite sure, but I think re-gearing to 4.10 with 31" will increase your mileage in city driving (because it will decrease the load on the engine)
while it will decrease highway mileage (because it will increase your RPM about 100 compared to 3.73 with 31" to achieve same speed)

 

[Ronin8002]

I'm not quite sure, but I think re-gearing to 4.10 with 31" will increase your mileage in city driving (because it will decrease the load on the engine)
while it will decrease highway mileage (because it will increase your RPM about 100 compared to 3.73 with 31" to achieve same speed)

I expect to see some result like this when I am able to drive some more. City driving will almost certainly have better fuel economy due to the reason you listed.

I am predicting that highway mileage will not be reduced by much. Before upgrading the axle gears, my transmission had to downshift out of OD very frequently (and run higher RPMs) just to maintain vehicle speed up long hills on the highway. With the higher gearing I do not expect that to happen as often...so I think that I might see an improvement in highway fuel economy. It will not be as good as it was with stock tires but it will be better than it has been since I have been running the larger ones.

 

[jd4242]

if you do alot of off roading or mountain driving i would go 4.56.don't fear the gear!!never know you might end up with 33s someday

 

[NHarris]

Thanks Ronin for that gear ratio/tire info!
And also a thanks to everyone who has had input on this thread.

I was now I'm runnin 33's on it and that's the OHV and did great on 31's barely a difference and since you have SOHC you should be set, unless you go to 33's I really wouldn't worry about it.

I doubt I will ever go larger than a 31" tire.


Off topic for a sec; the Ex is finally going to leave pavement this week or next week

 

[Glen4X4]

I doubt I will ever go larger than a 31" tire.
Off topic for a sec; the Ex is finally going to leave pavement this week or next week

Yeah I said that at one time : who knows you could change your mind someday. But awesome on going off pavement, going on a planned run with some people?

 

[Ronin8002]

Nate,

Here's a comparison of a lunchbox locker vs open vs limited slip performance. Granted its a powertrax lockrite locker in the demonstration but it's similar to the Aussie. Obviously it's not a perfect comparison since the vehicles are different but it will give you an idea:

http://www.youtube.com/watch?v=-S2nDDvKHoA

And here's another with a locked bronco and a LS explorer on offroad terrain. Little better comparison maybe since the vehicles are similar and they swapped tires to make it a more fair test maybe:

http://www.youtube.com/watch?v=-lydlwgiW6Y

 

[The Electrician]

Ronin the videos are great

but aren't rear locker's tend to over steer in tight corners?

and don't you guys with 3rd gen have braking traction control?

for me I really like Helical LSD with braking traction control,

a friend of mine who owns a v6 Toyota Fortuner with front and rear selectable diff-locks, and his truck is not more off-road capable than mine!

but on highway certainly mine is better than his (Helical LSD helps a lot) specially in slippery conditions

 

[The Electrician]

This a video clip of my truck with open diff and brake traction control


Important Note: Brake Traction Control requires maintaining a consent accelerator application even with a spinning wheel

Jerky accelerator will cause the traction control system to fail at the easiest of obstacles and stops the vehicle






Eited:
Trust me guys. with adequate ground clearance, proper trans gear selection (highest gear possible in low range) and brake traction control, the explorer is unstoppable