GBR 4.10 vs 4.75 gears - Defender Source
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  #1  
Old January 22nd, 2005, 03:05 AM
EdHsu
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GBR 4.10 vs 4.75 gears

With 33" tire, which gear sets will provide the best results in:

Top speed crusing ?
Gas milage?
Offroad driving?
Usable HP?
Strength?

Thanks.
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  #2  
Old January 22nd, 2005, 03:55 AM
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Nadim Samara
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If you do the math, 4.10s get you closer to the stock range than the 4.75s...eventhough I always prefer more gearing...


But to answer the below, 4.10s will do you better for 33s
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  #3  
Old January 22nd, 2005, 07:50 AM
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David Shechter
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In agreement with Nadim, 4.1
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  #4  
Old January 22nd, 2005, 09:32 AM
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Top speed cruise - 4.7 would be reving pretty high above 65mph
fuel mil -- 4.1 best
strenght -- 4.7 what strenght? the 4.7 is good for sand and mud. 4.7 is not as strong as the 4.1. Everyone I know who runs lockers and 4wheels on high traction surfaces has toasted a 4.7 set.
I run 4.1 with fr./rr lockers and 35s on high traction stuff . I have been good so far.
PS- while your in there add a locker
JP
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  #5  
Old January 22nd, 2005, 07:19 PM
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Toy swap and 4.56. 4.1 = weak 4.7 = weaker
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  #6  
Old January 22nd, 2005, 08:18 PM
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John B.
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>Top speed crusing ?
>Gas milage?
>Strength?

For those 3, the stock gearing is the best, then 4.1 and 4.75 last.


>Offroad driving?

What vehicle, gearbox, engine???? What type of off roading? Most people like lower, but it is not always the best.


>Usable HP?

On the road? Off road? Depends on the rest of the drivetrain, the weight of the vehicle, if you are towing......
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  #7  
Old January 24th, 2005, 10:03 AM
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Rob Goodall
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I have 4.7 and 35's I would suggest the 4.10 if you are running on the highway alot. My truck tops out at 63 mph due to the speedo hitting 95 mph. I have arb's and haven't broken anything yet.
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  #8  
Old January 24th, 2005, 12:01 PM
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Guys, Thanks very much for all your inputs, much appreciated.
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  #9  
Old January 24th, 2005, 12:17 PM
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Just curious. I have a friend that just pulled the 4.10's front and rear out of a '97 jeep and has offered them to me. Are these gears worth swapping out for my stock setup. I am running "33's and may want to go to "35's but not to soon.
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  #10  
Old January 24th, 2005, 12:22 PM
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would they work with the rover diff's?

Follow-up Post:

I think Hippert has 3:54's and 35" but he has the diesal t-case with the different ratio......
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  #11  
Old January 24th, 2005, 01:40 PM
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Quote:
Originally Posted by rover4x4
would they work with the rover diff's?

Follow-up Post:

I think Hippert has 3:54's and 35" but he has the diesal t-case with the different ratio......
They're not the same gears. I have a T-case with a 1.4 high range, the normal is 1.2, they help allot on the highway, I almost never downshift. But before the T-case swap I only shifted on big hills otherwise it was fine with 35s. But I have the same low range while the 4.1 gears will give you better high and low range the T-case will give you only a better High range.
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  #12  
Old January 24th, 2005, 06:23 PM
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So 4.10's would help but not these, right. Thanks for the info.
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  #13  
Old January 24th, 2005, 08:20 PM
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Can't the speed limiter causing a 63 mph max speed be fixed with that disco cold start Eprom? That's what I've heard, and hope to do when I switch to 4:10.
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  #14  
Old January 24th, 2005, 09:55 PM
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Rob Goodall
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Dave please tell me more.
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  #15  
Old January 24th, 2005, 10:12 PM
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Quote:
Originally Posted by souza
Can't the speed limiter causing a 63 mph max speed be fixed with that disco cold start Eprom? That's what I've heard, and hope to do when I switch to 4:10.
Yeah, it can, but why exactly would you want your truck winding out on the freeway at 70mph when your hitting 100+ mph rpm's on the tach. That terrible on the engine. 4.7 are not the right gearing for almost everyone here. And those that it is the right gearing for (ie 37's or larger) will break them in the blink of an eye. In a matter of fact, I just blinked, and broke a set. 4.10 is the right choice, if you can stand to shell out $1200 for gears without a problem. Before you do, call Rovertrax and talk to him about other, less expensive, stronger options. Or don't.
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  #16  
Old January 24th, 2005, 10:32 PM
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Dave Souza
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I saved this email from Doug Aitken on the D90 yahoo group because I thought I'd want to get this chip after I regeared (someday):

"I finally got round to swapping out my EPROM for the "Cold start" EPROM for a 3.9 ('94, '95) Disco to get rid of the annoying speed limiter which kicked in at just over 70 mph with my 4.10 R&P......

It could be purely psychological, but it seems like the engine runs much smoother and pulls better throughout the rev range (as well as the removal of the "brick wall"!).

Anyone else who has done this mod notice the same thing?

BTW: The part number has changed on this item: used to be PRM 3360A: it is
now PRM 3652.

Doug A"


Supposedly, it only costs like $17 dollars, and that's from the dealer. Be sure you don't get the 4.0 chip, it's for GEMS and is more expensive (and won't work!)
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  #17  
Old January 24th, 2005, 11:00 PM
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Johnathan Tisdale
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If you have a 94 you can drop a disco speedo gear in and do the same thing. I think it brings you back to around 3% error with 4:10s and 35s...takes about ten minutes and is cheap.

Tis
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  #18  
Old January 25th, 2005, 08:47 AM
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Rob Goodall
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I agree about the 4.10's I was talked into the 4.75's by the guys at rovertym 2 years ago and have wished for the 4.10's ever since. I am going to get that chip for when I need max speed to evade the police. No jail big enough!

Follow-up Post:

Thanks Dave, I ordered the part today.
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  #19  
Old January 25th, 2005, 01:56 PM
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Mike
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So what's the chip that I need for a '97 4.0 L? I do alot of street driving and some highway and mtn passes getting to the playgrounds. If I change to the 4.10, I want to lose as little highway performance as possible. I called RPI in the UK and talked to them about their chip. They change out 2 chips instead of one and man-o-man are they pricey. About $1300.
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  #20  
Old January 25th, 2005, 02:21 PM
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Dave Souza
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The chip with the numbers I posted is only for 94-95's with the 3.9, and it only disables the speed limiter as a side benefit... it's primarily to address cold start issues in some Disco's.

You have a whole different system on the 4.0, so I know it won't work. There may be one for the 4.0, but you'd have to check with the dealer (always fun). I seem to remember Doug's first attempt from the dealer resulted in a cold start chip for a 97+, which didn't fit. I could be imagining that though, it happens a lot .

I think the other option you'd have is a programable speedo, especially with the 97. I think you're speed limiter (if you have one) is fed via the speedo. If you get a programable VDO, it would send the correct speed to the computer, and you'd be fine.

And just to be clear, the only highway performance you'd 'lose' is gas mileage, caused by higher RPM at speed. If you have a speed limiter (I know my 95 does) you might hit it too soon, which is what I'm talking about trying to correct or eliminate. Otherwise the truck will seem faster, more powerful at any speed.
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