5" exhaust stack

[3up]

I've got a 934a2 and I'm thinking about putting a 5 inch exhaust on it taking it up above the box has anyone done that without a muffler.

 

[3up]

I've got a 934a2 and I'm thinking about putting a 5 inch exhaust on it taking it up above the box has anyone done that without a muffler.

 

[simp5782]

You don't need more than 4 really.

 

[3up]

But 5” looks so good

 

[Mullaney]

But 5” looks so good

.
I believe in this green MV truck business - there are "Wants" and there are "Needs" .

In some cases it needs to be one way or the other, but if you have a burning desire to have a five inch stack - it shouldn't hurt your power plant. There will be less backpressure, but without a muffler I would expect less.

Might want to investigate the sound in some form or fashion though.
If the (second seat) commander is unhappy with the noise - chances are you will be as well - or will be very soon!

 

[charlesmann]

My muffler was rusted out so i straight piped it. Operating the crane though is a bit loud w/o ear protection.
I also went with 4”, simply bc that is what factory was and that is what the local exhaust shop had in stock.
Sounds better but i wast going for sound, i just didnt want to buy a new muffler.

 

[Mullaney]

My muffler was rusted out so i straight piped it. Operating the crane though is a bit loud w/o ear protection.
I also went with 4”, simply bc that is what factory was and that is what the local exhaust shop had in stock.
Sounds better but i wast going for sound, i just didnt want to buy a new muffler.

.
Say what? I can't hear you!!

 

[3up]

I'm hoping that it will be quieter if it exhaust up above the box it will be loud outside but maybe not so loud inside. My girl that we were going to have to wear headsets like an airplane forever driving it so she was tickled it you don't have to do that.

 

[3up]

But 5” looks so good

.
Say what? I can't hear you!!

 

[3up]

I can always add a muffler later if it's too loud

 

[Mullaney]

I'm hoping that it will be quieter if it exhaust up above the box it will be loud outside but maybe not so loud inside. My girl that we were going to have to wear headsets like an airplane forever driving it so she was tickled it you don't have to do that.

.
Out up and away from the cab is good, but a muffler and 4 inch pipe might be a better plan.

You might want to search around for sound deadening. Heavy mats on the floor and the back wall for sure. Firewall insulation is important to hold down the noise. Heavy rubber "stall mat" on top of the stuff you stick to the floor (tractor supply. Plenty of reading to make the heat stay outside and that helps knock down the sound too.

Use your smart phone and download a free DB Meter. Run it as a base decibel measurement, then see how much difference just simple things like a heavy floor mat will to absorb sound. Then follow the reading and add more to make it better over time.

Couple of sound links:

Ramdough Cab Modifications Build Thread

My face when someone talks about me. ramdough coachgeo

www.steelsoldiers.com

M923a2 cab leaking water

Any body use something other than the cab seal kit to stop the cab from leaking? Plan to redo the whole cab, hard top. thanks

www.steelsoldiers.com

 

[3up]

Great idea I'll do that, I planned on Dyna matt the entire cab and fire wall The cab has like army green foam almost the thickness of like a sleeping pad stuck on it I'll be taking that off. I'm sure it was better than nothing

 

[Mullaney]

Great idea I'll do that, I planned on Dyna matt the entire cab and fire wall The cab has like army green foam almost the thickness of like a sleeping pad stuck on it I'll be taking that off. I'm sure it was better than nothing

.
It makes a world of difference in a "factory" cab. Without going out too far on a limb, more is generally better. Folks on YouTube have posted stuff there too and a lot of folks have gone from wearing headphones to actual conversation without screaming at one another.

"Broke Overland" has an entire series on his truck and the sound insulation is explained well. No stupid 8x video recording speeds and goofy music like a lot of the others IMO. He has a dedicated YouTube channel for his LMTV build. Not quite the same as your truck, but the principals apply for sure.

 

[3up]

Yes I have seen some of his videos he's A perfectionist and does a very nice job

 

[M936 Dave]

Great idea I'll do that, I planned on Dyna matt the entire cab and fire wall The cab has like army green foam almost the thickness of like a sleeping pad stuck on it I'll be taking that off. I'm sure it was better than nothing

hushmat is much cheaper than dynamat. I used a product called lizardskin spray on sound dampener. It reduced interior temps by at least 15° and cuts down on a lot of the racket. I too installed a 5" straight stack and should've went to a 60" to get the sound above the cab. Its annoying loud unlike my tweaked 3406b

 

[charlesmann]

hushmat is much cheaper than dynamat. I used a product called lizardskin spray on sound dampener. It reduced interior temps by at least 15° and cuts down on a lot of the racket. I too installed a 5" straight stack and should've went to a 60" to get the sound above the cab. Its annoying loud unlike my tweaked 3406b

Iv seen several youtube vids on that lizard skin and saw the db meter measurements, but of course that stuff could have been manipulated. Its good to hear about it from an outside user source.

 

[M936 Dave]

Iv seen several youtube vids on that lizard skin and saw the db meter measurements, but of course that stuff could have been manipulated. Its good to hear about it from an outside user source.

We use it a lot in our street rod,muscle car builds. I can promise you that it works. I have it in a 63 falcon and it has a.c. and before the lizardskin was sprayed inside and underside it worked ok or so so. After spraying it on just 3-5 mins of a.c. running it will frost the Windows up in 85-95° temps lmao. I have to turn it down to fan speed 1 and turn vent. Crazy how quiet it is inside as well no road noise Heck can hardly hear another vehicle coming up beside me. But emergency sirens or vehicle horns you can still hear very well.

 

[charlesmann]

That is good to know about sound and heat abatement.

Anyone here in this thread know the headache required to rmv, assemble and reinstall a 939A2 cab? Id like to fix up my spare cab, get it ready for instal and the rmv the cab from my operational tck and install it.