If the hf2av uses 3 gears to drive the output shaft in high range, how does the underdrive kit work? (1 Viewer)

[cody c]

I have one of those dB apps, it’s tough to isolate the gear noise on dB meter.

It’s very easy to hear the difference, but it lumps everything together. I.e. the gears might not be significantly louder than the 1FZ on the highway, but a significantly more intrusive frequency.

If I get the new idler, I’ll certainly try though. Steady speed 60, 70, 80 mph readings both in OD and in 3rd gear (to change engine rpm) would be more informative than 0-60.

Maybe just try leaving your phone at the trans tunnel, and do a few runs to get an average.

I run a diesel with 38" geolander MT's, used to have 37" mud grapplers. I don't think I would notice it so much but I don't use my 80 as a DD either, but I suppose if you run AT's and commute at 80mph daily it would be significant.

 

[Delta VS]

Just need an app like this (called "Spectrum Analyzer" on iOS, free). It has a constant live feed of frequencies, and that light blue volume in the back is recorded peaks. Should be able to take a screenshot before a drive and during a drive. If there is actually a particular frequency jumping up due to gears, you should be able to see it here.

 

[Shoredreamer]

Anybody try heavier gear oil to combat any noise from the gears?

I’m no gear pro or anything but from my observations when I rebuilt my case with UD and 3:1 gears, the UD gears seemed to have a different shape and thickness to them vs. the stock gears. I heard rumors of a lot of noise after UD install from others and was a bit worried I might regret dropping in these gears for minimal benefit. I also thought why wouldn’t they change out the 3rd (idler) gear too? Anyway, continued on with the regear hoping for the best. I finished last week and have put the new high and low gears thru a good break in of mountain roads, sustained highway and wheeling at the local off road park. So far the underdrive gears have me pretty happy. I daily drive my truck and put on 15k miles a year. Rolling on 35s at over 7000#s, the truck drives and shifts a lot better. I rarely drop into second now and have a bit more pep when stomping the pedal. The UD gears make a tiny bit of noise but it’s really nothing worth mentioning for me. Seriously with no music on and windows up, I hear a tiny wind/whine, that’s it. But my tranny, snorkel, tires and 1st gear (A442) are much louder. Maybe in a completely stock 80 you’d notice the noise pretty easily.

Still, I’m regearing 2 more cases currently for a couple other 80s and I’d be curious what differences the modified idler would make.

 

[HDJdreams]

Running 50:50 Amsoil 75W-90 and Lucas oil. Didn’t notice much difference.

 

[DanMedeiros]

Anybody try heavier gear oil to combat any noise from the gears?

I’m no gear pro or anything but from my observations when I rebuilt my case with UD and 3:1 gears, the UD gears seemed to have a different shape and thickness to them vs. the stock gears. I heard rumors of a lot of noise after UD install from others and was a bit worried I might regret dropping in these gears for minimal benefit. I also thought why wouldn’t they change out the 3rd (idler) gear too? Anyway, continued on with the regear hoping for the best. I finished last week and have put the new high and low gears thru a good break in of mountain roads, sustained highway and wheeling at the local off road park. So far the underdrive gears have me pretty happy. I daily drive my truck and put on 15k miles a year. Rolling on 35s at over 7000#s, the truck drives and shifts a lot better. I rarely drop into second now and have a bit more pep when stomping the pedal. The UD gears make a tiny bit of noise but it’s really nothing worth mentioning for me. Seriously with no music on and windows up, I hear a tiny wind/whine, that’s it. But my tranny, snorkel, tires and 1st gear (A442) are much louder. Maybe in a completely stock 80 you’d notice the noise pretty easily.

Still, I’m regearing 2 more cases currently for a couple other 80s and I’d be curious what differences the modified idler would make.

Yeah Chris lets throw the idler gear in mine!

 

[mct75]

So the gears have more/less teeth but are the same diameter? That seems really wonky!

 

[TurboDennis]

One should just take a stock, quiet t-case and do a pattern check on the teeth, (same way as done when setting up a differential) before installing the modified gear set. Then install the modified gear set and re-check the pattern. Then do the same with the modified idler gear. Compare the 3 patterns and they will tell you all you need to know about noise. Noise is a result of improper gear meshing, which will be clearly visible on the pattern check.

 

[cruiseroutfit]

Back in town and catching up here gents. I still don't have a resolute answer on when to use the aftermarket idler assembly. What we do know is the gears themselves can have a bit of additional noise, levels seem to vary based on age of install and perhaps additional factors such as tires, roof racks, etc. I've heard from at least two that have the idler gear/shaft and didn't notice any difference in noise or more appropriately they still have a bit of noise. Hardly scientific I know I still need to have a minute to dig through the gears and determine if this is ideal for the under-drive or the over-drive sets, it simply can't be ideal for both any more than the stock gears work for both. I pinged a friend overseas that has been selling/using these overdrive/underdrive gears in builds for more than a decade, he wasn't even aware there was an aftermarket idler gear outside of stock applications.

More pics of the gears fwiw (still coated with cosmoline

 

[wardharris]

As a non-technical person with an interest in the topic, this is a great thread. Excellent example of why/how MUD is such a valuable resource for this community.

Thanks guys!

 

[DanMedeiros]

Thanks Kurt! This may be going into my tcase depending on what you figure out

 

[baldilocks]

As a non-technical person with an interest in the topic, this is a great thread. Excellent example of why/how MUD is such a valuable resource for this community.

Thanks guys!

But, in true Mud form, this thread implies a problem or deficiency where none has been documented other than some alleged noise that has only been reported by a few.

Per my experience, with these low range gears from Japan, not China, noise levels are actually lower than before. I used a transfer case from my wrecked 94 that was always quieter than the one that was in my 93 (similar miles) when I bought it.

A good sound deadening material and new insulation, which many do anyway, including myself, should be enough to block any extra decibels perceived by delicate ears.

Opinions and empirical data is all over the chart so, is there an actual problem, or is Mud just bored? Not once has anyone, including my wife who has ridden on long road trips with me in my 80 with these gears, ever commented “what’s that noise”?

In fact, recently a co-worker and I drove my rig 2000 mostly all highway miles and he was astonished at how quiet it was with 37” trXus Mud terrains.

I have my proverbial bucket of popcorn ready to see where this one goes.

 

[mct75]

I still am in the camp of "it's impossible without the idler gear moving closer to the smaller drive/driven gear" but obviously I am wrong so I have something to learn.

 

[wardharris]

But, in true Mud form, this thread implies a problem or deficiency where none has been documented other than some alleged noise that has only been reported by a few.

I have my proverbial bucket of popcorn ready to see where this one goes.

Agreed and agreed. My partner Georg @orangefj45 IS a tech expert and we sell the same gears - crawler, OD, UD - from the same Japanese factory. In our experience, the mod gears are a proven (and quiet) solution for a range of needs. Lots of happy customers regardless of the reseller or installer. Kurt provides great service to this community and Kurt's comments above are a testament to his willingness to listen to feedback and respond.

For what its worth, my popcorn is ready to follow this conversation as we have a new show truck on the way, a big blue unicorn with a brand new HF2A TC that will be used for long distance highway travel to events on highway tires. Among other things it will get some Harrops and auto transmission swap from Australia - right behind a freshly rebuilt 1HZ. We will be fine tuning the truck to produce the best combination of engine output, revs, transmission gearing, r&p gearing, tire diameter, etc. The R&P ratio and TC mod gears are the frosting on our drivetrain cake.

Given that I will be spending weeks of my life in this thing, the noise level from all sources will be the subject of much effort and investment - along with some Scheel-Mann seats for my aged and worn body....

Along with Dynamat, carpet, etc. we will work hard to mnimize the added noise from the mod gears. The truck will not have traction or mud tires, so it should be a relatively "quiet" platform for testing and analysis.

Georg says there IS some minor change in noise level - we will use the Blue Unicorn to research why, what, how, etc. of gear sets, idlers, case condition/rebuild, etc. over the next year.

Thanks for the conversation!

Ward

 

[cody c]

One should just take a stock, quiet t-case and do a pattern check on the teeth, (same way as done when setting up a differential) before installing the modified gear set. Then install the modified gear set and re-check the pattern. Then do the same with the modified idler gear. Compare the 3 patterns and they will tell you all you need to know about noise. Noise is a result of improper gear meshing, which will be clearly visible on the pattern check.

I know where your going, but I think it's a bit different with a pinion gear, as the pinion gear comes into contact with the ring gear you can see where the faces meet, and then you adjust to ideal location with shims, with these transfer case spur gears, the contact point shifts from the outer tip and moves inwards, or for the other gear it goes from inner to outer but your contact patch shifts. Having said that, I'm not sure what you'd be looking for or expect to find, maybe a point at the gear tip or inner where there isn't contact I guess, but you should be able to tell that from surface wear. But if the gears are designed properly, it shouldn't matter. You might find more with frequency graph, if you know a given RPM, and you can find a frequency, you can find a gear or component that correlates, or even bearings that correlate.

This short YouTube video link should help to visualize what I mean


I've been playing with gear profile design with AutoCAD lately so now I'm a know it all, my background is electrical (industrial electrician/drafter/designer/modeller)

 

[baldilocks]

Agreed and agreed. My partner Georg @orangefj45 IS a tech expert and we sell the same gears - crawler, OD, UD - from the same Japanese factory. In our experience, the mod gears are a proven (and quiet) solution for a range of needs. Lots of happy customers regardless of the reseller or installer. Kurt provides great service to this community and Kurt's comments above are a testament to his willingness to listen to feedback and respond.

For what its worth, my popcorn is ready to follow this conversation as we have a new show truck on the way, a big blue unicorn with a brand new HF2A TC that will be used for long distance highway travel to events on highway tires. Among other things it will get some Harrops and auto transmission swap from Australia - right behind a freshly rebuilt 1HZ. We will be fine tuning the truck to produce the best combination of engine output, revs, transmission gearing, r&p gearing, tire diameter, etc. The R&P ratio and TC mod gears are the frosting on our drivetrain cake.

Given that I will be spending weeks of my life in this thing, the noise level from all sources will be the subject of much effort and investment - along with some Scheel-Mann seats for my aged and worn body....

Along with Dynamat, carpet, etc. we will work hard to mnimize the added noise from the mod gears. The truck will not have traction or mud tires, so it should be a relatively "quiet" platform for testing and analysis.

Georg says there IS some minor change in noise level - we will use the Blue Unicorn to research why, what, how, etc. of gear sets, idlers, case condition/rebuild, etc. over the next year.

Thanks for the conversation!

Ward

My low range gears and case swap was done by the gang at Valley Hybrids. These guys are outstanding in technical knowledge, ability, and their customer service is personal and beyond great.

 

[cody c]

My lownrange gears and case swap was done by the gang at Valley Hybrids. These guys are outstanding in technical knowledge, ability, and their customer service is personal and beyond great.

And how is the noise?

 

[baldilocks]

And how is the noise?

I honestly didn’t notice any difference. Before I added sound deadener and new insulation, there was an audible high frequency hum, audible not deafening or any worse than mud tires. However, it was not outstanding to the point where i was defiantly sure that the new gears were any louder than the stock gears. I would not expect a gear driven transfer case to be silent.

Now that we know the idler gear is available, anyone doing a gear install can just order it as part of the kit and know that the install was done good as could be.

Let’s not forget that most negative reports are issued by a very loud minority.

 

[mudgudgeon]

But, in true Mud form, this thread implies a problem or deficiency where none has been documented

Ah, yes. Ih8mud, solving problems before they ever existed and enabling OCD since 2002!

right behind a freshly rebuilt 1HZ. We will be fine tuning the truck to produce the best combination of engine output, revs, transmission gearing, r&p gearing, tire diameter, etc. The R&P ratio and TC mod gears are the frosting on our drivetrain cake.

You won't need to worry about gear noise, the injection rattle of the 1HZ will down out the gear noise

 

[rc51kid]

But, in true Mud form, this thread implies a problem or deficiency where none has been documented other than some alleged noise that has only been reported by a few.

Per my experience, with these low range gears from Japan, not China, noise levels are actually lower than before. I used a transfer case from my wrecked 94 that was always quieter than the one that was in my 93 (similar miles) when I bought it.

A good sound deadening material and new insulation, which many do anyway, including myself, should be enough to block any extra decibels perceived by delicate ears.

Opinions and empirical data is all over the chart so, is there an actual problem, or is Mud just bored? Not once has anyone, including my wife who has ridden on long road trips with me in my 80 with these gears, ever commented “what’s that noise”?

In fact, recently a co-worker and I drove my rig 2000 mostly all highway miles and he was astonished at how quiet it was with 37” trXus Mud terrains.

I have my proverbial bucket of popcorn ready to see where this one goes.

Stupid question just for 100% clarity. Are you using lower lower range gears AND the lower high range gears that the thread is discussing?

 

[baldilocks]

Lower low range gears only..