Regearing to 4.88s

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Feb 23, 2011
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543
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Boise, ID
I have 33'' tires and want a bit more power while towing, especially in the mountains here. There's a 7% grade hill that I can currently make it up with our ~4k lb camper, but I have to floor it at around 50mph in 2nd gear, and it slowly loses RPMs as I approach the top. I think the 4.88s will fix this, plus the 200k diffs need to be gone through, I'd imagine. This should also bring me back within 2% accuracy on my speedometer, from what I was reading earlier here. My tires are ~9% larger circumference than stock, and these gears will adjust back down ~7.3% iirc.

So, what brand should I go with? JustDifferentials has this kit, but I'm not sure if it matters that the gears are made in Korea.

I'm thinking about having LTS motors do the regear, though that will cost me about $1600 in labor. To me this seems acceptable because I've never split a pumpkin and likely don't even have the right tools to get the job done, and I want to make sure it gets done right.

Thoughts? Suggestions? Brands to look at?
 
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Miami
I just the justdifferentials kit. Went to 4.88. You speed will be way off with 33s. I am running 34s and it reads 5% faster on gauge than on gps. Think I would need 36s to make it back to factory.
The kit is good. No instructions and the seals seem to be inexpensive ones. I put Toyota ome seals on half after the first ones had problems.

Did the install myself. Also added arb lockers. Spent about 200 in tools. Got a parts washer, new calipers, brass drifts, dial indicator and the rest I already had. In end glad I did it myself. Very steep learning curve. Got some great mentorship from some ih8 members. But lots of work.

good luck. my 2 cents don’t regear with 33. Expensive and lots of work. You will get more power but lose mpg.
 
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Dec 29, 2014
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993
I did a transfer case underdrive regear in May from @cruiseroutfit . It’s been 7,000 miles and I am very pleased. I pull a 3500lb trailer and am running 33” with slee bumpers and skids (to give you some weighty facts).

I also did the low range and the extra low helps the control and feel off road. I run 35”s on the trails.
 
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Interesting, that t-case regear sounds like it would do what I need... are these what I'd need?


80/100 High Range 10% Underdrive Gear Set - 8x/100 Series Land Cruisers
Fits 1/1990-1/1998 8x Series/LX450 and 98-07 100 Series Land Cruisers/LX470 (100/470 applications require additional parts, call for info). Fits factory full-time (HF2A/HF2AV) transfer cases found in US Spec and global market Land Cruisers. These gears offer a 10% underdrive in high range, equivalent to converting axle gears from the 4.10 to 4.56 gears without having to do ring & pinion work.
Part# TCG9007UDHR - $505.00

80/100 3.1:1 Low Range Reduction Gear Set - 8x/100 Series Land Cruisers

Fits 1/1990-1/1998 8x Series/LX450 and 98-07 100 Series Land Cruisers/LX470. Fits both factory part-time (H1FA) and full-time (HF2A/HF2AV) transfer cases found in US Spec and global market Land Cruisers. Includes both low speed output gear and idler gear. Minor case clearancing is required using a die-grinder, otherwise these are a direct fit to your 80/100 Series transfer case. Factory ratio is 2.49:1, these 3.1:1 gears offer a 25% low range reduction with no change to the 1:1 high range. Made in Japan to OE Toyota specifications.
Part# TCG900731 - $725.00
 
Joined
Feb 23, 2011
Messages
543
Location
Boise, ID
I just the justdifferentials kit. Went to 4.88. You speed will be way off with 33s. I am running 34s and it reads 5% faster on gauge than on gps. Think I would need 36s to make it back to factory.
A lower gear ratio will compensate on your speedometer for bigger tires... for example:

Stock
2300 RPMs
31'' tires
4.30
Speed = 49.3mph

33s with 4.56
2300 RPMs
33'' tires
4.56
Speed = 49.5mph

33s with stock 4.30
2300 RPMs
33'' tires
4.30
Speed = 52.5 mph

 
Joined
Aug 28, 2012
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Location
Battle Ground WA
I did a transfer case underdrive regear in May from @cruiseroutfit . It’s been 7,000 miles and I am very pleased. I pull a 3500lb trailer and am running 33” with slee bumpers and skids (to give you some weighty facts).

I also did the low range and the extra low helps the control and feel off road. I run 35”s on the trails.
Do you notice any gear whine with the new Tcase gears?
 
Joined
Dec 29, 2014
Messages
993
Do you notice any gear whine with the new Tcase gears?
Yes, I have a whine noise up to about 2200rpm. It has not changed much, so it not a wear in thing. That said, I am used to it. I have DT cat backs which pretty much drown out everything. :D

All in, I would do it again.
 
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Jackson, WY
@RiverRatMatt i am leaning towards T case regear and lock the front diff. I like to drive 80+ and think that the slightly lower ratio of the arcade High would be better for me than 4.88s

Can you comment on driving over 75?
 
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Dec 29, 2014
Messages
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@RiverRatMatt i am leaning towards T case regear and lock the front diff. I like to drive 80+ and think that the slightly lower ratio of the arcade High would be better for me than 4.88s

Can you comment on driving over 75?
Driving over 65 is not legal in my state, so I never drive over the speed limit. :rofl:

Ok, so in other states..... over 75 is fine (33’s). It does not feel topped out or anything. Passing top speed is generally in the upper 80’s. I would also say the downshift point does not come into play nearly as much. That allows cruise control to maintain say 73mph in mild rolling hills with little downshifting. Big hills it’s going to down shift out of 4th.

I do drive on road with the 35’s to get to wheeling events. I will not comment yet on that only because, my 35’s are worn out, only about 34’s. Also I did 400miles right after I re-geared and I don’t have a strong memory of what it was like.
 
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Driving over 65 is not legal in my state, so I never drive over the speed limit. :rofl:

Ok, so in other states..... over 75 is fine (33’s). It does not feel topped out or anything. Passing top speed is generally in the upper 80’s. I would also say the downshift point does not come into play nearly as much. That allows cruise control to maintain say 73mph in mild rolling hills with little downshifting. Big hills it’s going to down shift out of 4th.

I do drive on road with the 35’s to get to wheeling events. I will not comment yet on that only because, my 35’s are worn out, only about 34’s. Also I did 400miles right after I re-geared and I don’t have a strong memory of what it was like.
Thanks. I travel through WY alot and the speed limit is 80 in a lot of places so sometimes passing you are going from 75-85. I just put on heavier Wheels and tires so trying to plan a bit. I still want to be able to cruise at 80 comfortably. I have cruised in other countries in my 100 at 85-90 on 285 75 16s with RPMS at 3100-3300 and it didnt bother me one bit. If doing 80-85 with the Transcase gears is similiar 3100-3300 It wont bother me one bit....
 

nukegoat

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Underdrive gears inherently try to mesh a different gear pitch with an OEM gear. I don't like the idea at all
 
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I always feel the need to remind those considering regearing their differentials that you will be weakening the unit by going to a higher numerical ratio, as it involves a smaller pinion gear. Yes, I'm well aware that many owners successfully put hundreds of thousands of miles on such combinations; nevertheless, you are weakening the unit and thus reducing the margin of safety, particularly if you combine it with larger-diameter and heavier tires. Just another thing to consider.
 

hoser

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4th gear on the 5-speed transmission is also the strongest gear choice as it is direct drive, 1:1.

But Toyota decided we could have 4 other gear choices because the pros outweighed the cons. ;)
 

nukegoat

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I always feel the need to remind those considering regearing their differentials that you will be weakening the unit by going to a higher numerical ratio, as it involves a smaller pinion gear. Yes, I'm well aware that many owners successfully put hundreds of thousands of miles on such combinations; nevertheless, you are weakening the unit and thus reducing the margin of safety, particularly if you combine it with larger-diameter and heavier tires. Just another thing to consider.
The first part isn't true. Gears are levers. Applying the lever closer to the fulcrum gives you greater mechanical advantage. It doesn't make the forces on the lever overall any different. The small pinion gear argument is dumb and ignorant.

Since lower gears let you apply more torque to an axle shaft, though, the shafts are at greater risk with big tires and low gears.
 

nukegoat

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4th gear on the 5-speed transmission is also the strongest gear choice as it is direct drive, 1:1.

But Toyota decided we could have 4 other gear choices because the pros outweighed the cons. ;)
Also AHC in L is the best because it keeps the driveshaft misalignment to a minimum, maximizing u joint strength. And CV strength.
 
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The first part isn't true. Gears are levers. Applying the lever closer to the fulcrum gives you greater mechanical advantage. It doesn't make the forces on the lever overall any different. The small pinion gear argument is dumb and ignorant.
What a stylish response. However, it is your argument that isn't true, as five minutes of research would show you. Just one authoritative example here, from one of the largest aftermarket suppliers of differentials. Go read it and then perhaps rethink your attitude. Regearing a differential to a higher numerical ratio weakens it, period. As I mentioned, there is sufficient leeway in the strength of most differentials to allow such modifications if you don't go overboard; nevertheless, you are compromising the strength of the unit. When combined with the extra stress of larger and heavier tires, the effect is exacerbated.
 

nukegoat

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What a stylish response. However, it is your argument that isn't true, as five minutes of research would show you. Just one authoritative example here, from one of the largest aftermarket suppliers of differentials. Go read it and then perhaps rethink your attitude. Regearing a differential to a higher numerical ratio weakens it, period. As I mentioned, there is sufficient leeway in the strength of most differentials to allow such modifications if you don't go overboard; nevertheless, you are compromising the strength of the unit. When combined with the extra stress of larger and heavier tires, the effect is exacerbated.
What an uninformed response

I'm sure these gears fall apart then:

 
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