[Krishnamoorthi]

Dear BHPians

My Armada has a DI Turbo engine and an NGT 520 4x4 gearbox (Engine and gearbox are from two different vehicles). The front housing is a two wheel drive (thought of fitting the front wheel housing when I get a good one at a reasonable price).

Coming to the problem. I got the 4x4 NGT 520 gearbox aftermarket. I dissembled the entire gearbox, changed the synchronizers, fifth and reverse gear assembly and made a complete overhaul and fitted to the engine.

There comes a sound from the gearbox and clutch area when the engine is running in neutral. When I press the clutch and release it, the sound reduces but not completely. The sound seems to be more while driving in 3rd and 5th gears. The gear shifts seem to be ok.

I have changed the crown too - but the noise still persists.

What might be the problem. Please give some suggestions or solutions. Thanks in advance.

[Jaggu]

Originally Posted by Krishnamoorthi

There comes a sound from the gearbox and clutch area when the engine is in running in neutral. When I press the clutch and release it, the sound reduces but not completely.

Sound in neutral and changing with clutch activation, you need to get the clutch assembly, release bearings etc.

The sound seems to be more while driving in 3rd and 5th gears. The gear shifts seems to be ok.

What kind of sound is this? Is it some kind of booming or mechanical chatter?

[Krishnamoorthi]

Thanks for your reply

The sound seems to be a clatter noise. The clutch assembly and release bearing are change new while overhauling the GB. still the sound persists.

[Jeroen]

Like Jaggu my first thought would be release bearing. There are a few other thoughts too.

Not sure if it applies to your gearbox/engine. Usuaslly the input shaft into the gearbox also slides into a bearing in the engine cover. Very often it is just a simple bushing. These are often overlooked. If they are a bush, they need to be left to soak in oil 24 hours before installing.

They can cause all sorts of whining noises. Usually more pronounced in reverse!

There could be another simpler explanation too; insufficient or incorrect sound proofing!
I once thought I had a similar problem on an Alfa Romeo. When I started investigating I found that several of the rubber boots between gearbox, chassis and gear lever were badly torn. Replacing them was sufficient to get rid of all the noise. If the noise is more pronounced when the transmission oil is cold, compared to warm, it’s worth investigating.

As you put a different gearbox in, whatever was in place might simply not be sufficient. Gearboxes do make sounds, and you might have gotten unlucky with this combination.

Good luck.

Jeroen

[Krishnamoorthi]

Thanks Jeroen.

I will try checking my release bearing in this regard.

[Jaggu]

Check the alignment of the box to the engine, and if there is any excessive play anywhere. Since it is a used gearbox one will have to go through in detail through all of this.

[jeeva]

Originally Posted by Krishnamoorthi

Thanks for your reply

The sound seems to be a clatter noise. The clutch assembly and release bearing are change new while overhauling the GB. still the sound persists.

Clutch fork it must be!

[dhanushs]

I would suggest check the release bearing, pressure plate and clutch fork.

If this seems to be OK, then the GB main shaft bearings. NGT520 gearboxes usually need to be overhauled from not a regular jeep workshop, but, a reputed one. Not as easy as the KMT90.

[DirtyDan]

Originally Posted by Jaggu

Check the alignment of the box to the engine, and if there is any excessive play anywhere. Since it is a used gearbox one will have to go through in detail through all of this.

Yeah, this and the proper torque of the bolts along with it. This is an easy and inexpensive thing to check first. You might have him slap a little grease on the driveshaft universal joints (crossovers) while he is under there fooling around.

Even brand new manual trannys/clutches will make a certain amount of clatter which will greatly diminish when you depress the clutch...hope this works out for you.

[GTO]

Originally Posted by Krishnamoorthi

The gear shifts seems to be ok.

I have changed the crown too - but the noise still persists.

Slightly different view from another owner of an old Jeep. The shifts are okay as is the functioning. I have learnt to ignore undesired sounds & noises in my '97 Jeep as long as there are no other signs of anything being seriously wrong. Solve one and another one surfaces. Even when she was brand new, there were 5 - 10 sounds that shouldn't have been there!

[condor]

To add a point about the release bearing:

You mention the vehicle being an Armada .. i.e, an older model. The Sumo's / other Tata light vehicles from 15-20 years back (also TCIC), had a similar problem in stock setup. Release bearing noise in those vehicles can be stopped temporarily by adding some tape, but will eventually return. I had checked with my SA on such noise, and he said to just leave it as it is.

But one aspect of the release bearing noise in these Tata's was the noise also comes when changing gears.

(Note: not my old Sumo Victa TCIC ... that one was a beauty without any such issues).

[ringoism]

Originally Posted by Jeroen

Not sure if it applies to your gearbox/engine. Usuaslly the input shaft into the gearbox also slides into a bearing in the engine cover. Very often it is just a simple bushing. These are often overlooked.
They can cause all sorts of whining noises. Usually more pronounced in reverse!

This is called the clutch pilot bearing, and it mounts in the end of the crankshaft, and yes, often overlooked.

But his symptoms don't seem to match:



As for the basic mechanical combination, there should be no issues, since the components are basically same as what's used in M&M Bolero/ later-model Camper 4x4.

Yes, release bearings sometimes make noise, and alignment/adjustment of the release fork can also be a contributing factor. With that bearing bad, you'd probably have a vibration in the clutch pedal, and it's less usual for the noise to be present when released.

But being that the noise seems more pronounced when in particular gears (3&5), I might tend to suspect (my apologies) that something was reassembled incorrectly/imperfectly... even an out-of-spec thrust washer or something like that...

You did not mention changing the mainshaft/countershaft bearings, and that's what I'd suspect more... just a little roughness there can create noise.

It's a bit difficult to get a sense of the sound and noise levels, but Jeroen's comments re: typical gearbox noise and requisite sound insulation also seem worthy of consideration. Our Marshal got a LOT quieter - KMT90 and everything else - when I put a couple rubber sheets over the (similarly rebuilt) gearbox and floor hump, tight around the gear lever. My wife added a couple layers of 10mm closed-cell foam sheet to the whole front floorpan & kick-panels, and Alas! The beast started to sound almost tolerable and "modern"!

-Eric

[DirtyDan]

Originally Posted by ringoism

This is called the clutch pilot bearing, and it mounts in the end of the crankshaft, and yes, often overlooked.

But his symptoms don't seem to match:


But being that the noise seems more pronounced when in particular gears (3&5), I might tend to suspect (my apologies) that something was reassembled incorrectly/imperfectly... even an out-of-spec thrust washer or something like that...

Hmmm.....our thread starting guy is now banned? Was it his response to our bumbling/stumbling suggestions that zapped him?

Next to my own wonderfully insightful and intelligent response above, I like Ringo's response here. One of the new synchronizers itself may be a bit out of spec....not an uncommon Mahindra phenomenon. If the pilot bearing fails, that's "all she wrote", the symptom is...you ain't goin' anywhere. Noise? There is an old North American joke about odd noises in cars and the universal solution...."Turn up the radio."