LUVTruck.com

Oh man, things just keep getting better.

Now I have a constant, loud whine in 4th gear when driving around 60-65 on the freeway. It gets louder if I accelerate, and goes away completely if I let go of the pedal. Could it just be low on fluids? Or is my pilot bearing toast? I'm going to pull the shifter tomorrow and attempt to fill it, or at least stick a magnet down there to see if there's any metal. Hopefully it's just low on oil, I can fill it with some 10w30 and the noise will go away. But I have a feeling with all my wonderful luck lately that this is just the beginning. ha.

Thanks for any input!

Also.. I'd absolutely LOVE to swap out this transmission and stick in a 5 speed. Oh man. So any tips or ideas on where I can find one that fits. I know some of the pups, and if I remember reading correctly, the troopers can be a direct replacement?

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Not a Trooper, unless your truck is 4wd. Your best choice would be any 5-speed that was used on an Isuzu 2.3 gas engine. It was available on:
1986-87 P'up
1988-95 Pickup
1988-94? Amigo

These would all require a new slip yoke, because they have a 27 spline output shaft.

The earlier 5-speeds can be used, but they are really prone to failure.

Jack

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'83 Isuzu P'up Diesel LS - Original Owner
JoeIsuzu@IsuzuPup.com
IsuzuPup.com

Why not just remove the drain & fill plugs on the tranny? The drain plug is magnetic, you shouldn't have anything more than a silvery sludge on it. When the lube runs out the fill hole it has the correct amount, whether put in through the shifter or the fill hole. You don't know if it's low or not without the fill plug level as a guide, if you overfill it will start leaking at a seal.
The noise is not your pilot bearing, the pilot bearing only turns when the flywheel & tranny input shaft are spinning at different speeds. Any time the clutch pedal is up the flywheel & input shaft are locked together via the clutch.
I've never had a tranny exhibit symptoms like you describe, & I've been through more than my share of trannies. The most usual noise is an input shaft bearing that starts making noise when idling with the tranny in neutral & clutch pedal up. A loose pinion nut on the rear end makes a noise more like you describe, except the opposite- usually quieter on acceleration or steady pedal, then louder during coast- so make sure the noise is coming from the tranny & not the rear end.
By the way, is your truck lowered a bunch? I have been involved in diagnosing noise in a couple of drastically lowered trucks, turns out the lowering was enough to shorten the distance between the tranny tailshaft and the pinion flange so that the driveshaft was slightly too long. When the driveshaft was installed it pushed into the tailpiece so much than it sideloaded the bearing & caused a noise. Just slightly shortening the driveshaft so that the slip yoke didn't bottom on the tailshaft fixed the noise. You can check by unbolting the shaft flange at the pinon flange when the truck is at normal ride height & seeing if the driveshaft will push farther into the tranny tailpiece. If it won't your shaft needs shortening.

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'78 Chevy LUV,1.9,4sp,headers,31's,SAS Dana 30,Dana 20,SOA rear w/Aussie Locker, rough body, bought new 12/4/78.
'87 Trooper,2.3,5sp,headers,31's,ball joint flip & spacer,Aussie Locker rear,Superwinch hubs,brush guard w/5.5K winch,more to come.

It just started happening as well. I don't have any carpet in the truck anymore, ripped it out several years ago, and the shifter boot is torn so I can hear that it's coming from somewhere down there. If I cover up the hole I can hardly hear it again, but it's only when the gas pedal is down in 4th gear. If I let off the gas, no more whine. I'm wondering if maybe it has something to do with my electrical? Someone rerouted my fuel pump so it would turn on with the key on and now all these issues are popping up.

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Drain it all out and refill with fresh oil and see if it does anything. If you are gonna get under the truck anyway you may as well do it

I fly back Saturday morning are you free Sunday?

Also if you decide to hit up picknpull for a 5 speed let me know I have been dying to use my cordless sawzall there

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Luvless
1980 Mikado-Sold.

1993 Lexus SC400 my Daily
2004 Yamaha WR250F my new love in life
2016 Toyota Camry my girls ride

Noise that changes with acceleration or deceleration is nearly always rear end related, not transmission. I would look there.

I have the trooper 5 speed. It was making a really loud whining and I took it in. Cost 2k for a full rebuild.

Trooper 5spd has a mated transfer case so you'd need a 4wd truck and I needed an extra cross member.

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1979 4wd Mikado. G200, Gemini 250 Turbo, Clive Cam, Offenhouser Intake, JE Pistons, maXspeeding Forged Rods, Blow Thru Weber, Trooper 5spd, Intercooled

If it's only whining at a certain speed, it's probably not the transmission. Mine did that and it was a u-joint.

Mine whined like that, and it WAS the transmission (both times). However, it was in other gears, not 4th. Countershaft bearings are the usual points of failure with this transmission. Since 4th gear does not use the countershaft, it can be quiet in 4th even with bad countershaft bearings. If it's noisy in 4th, I'm inclined to agree with egg and maybe oldestisuzuist--it may be the rear end, or something else.

Jack

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'83 Isuzu P'up Diesel LS - Original Owner
JoeIsuzu@IsuzuPup.com
IsuzuPup.com

Thanks for all the info. I'll take a look at the rear end see if I find any loose u-joints or anythings. Thanks!

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I was experiencing pretty much exactly what SkyyPayne describes - a loud rumble in 4th while accelerating, but the sound disappears if I let go of the pedal or otherwise apply a negative load to the drivetrain(e.g. downshift)

As oldestisuzuist and others have mentioned, the pinion nut was the culprit. I brought it to my local mechanic and he dropped the drive shaft and tightened the bolt for $20. To my disbelief, no more rumble. Zero.

Now I feel like I'm flying on the freeway, instead of tiptoeing around the awkward 55mph 'rumble zone'. It feels amazing.

It was easy to diagnose with a little tugging on the driveshaft around the rear u-joint. Any play between the shaft and rear end is immediately obvious. I don't know why I thought it would be harder to solve.I put it off for so long thinking that I'd for sure need a rebuilt rear end, but damn am I glad I finally checked.

I imagine the reason that the exact speed the rumble is different for some of us may be due to a few things - how loose the nut itself is, the gear ratio of the specific diff, etc..

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75 Mikado G180/4sp Desert Tortoise