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Rounded_nut · 07-06-2019, **(Subject: CHanging rear end, paccar motor )**

Heya folks, long time no chat. Anyways, I got a 455hp MX13, EPA2013, 13 speed and 3.08 rears. It's been doing just fine with the usual light loads (10k lbs), however I'm leaving that gig and will be at gross everywhere but a fair amount of NW, so mountains. I'm looking to swap out the rears to 3.7x, used/rebuilt, however I'm wondering about cruising rpm's, specifically how the engine performs cruising loaded at 1400-1600 rpm. Torque peaks at 900, rpm limit is 2200 so I'm thinking it should do just fine at 1500 rpm, just not sure how this pushrod engine likes it. I know just by giving it a better lever that'll help, as well I don't intend to keep it floored going up the hills. With the god awful 3.08 rears a gross load over a speedbump is rough enough!

Adding on, going with used/rebuilt carriers does $2k sound about ball park to swap out?

Running low pro 22.5.

Rawze · 07-07-2019, **(Subject: CHanging rear end, paccar motor )**

weller re-mans are not a bad option if you want something that has been properly re-worked.

Rounded_nut · 07-07-2019, **(Subject: CHanging rear end, paccar motor )**

Thanks for the recommendation.

Lonestar10 · 07-07-2019, **(Subject: CHanging rear end, paccar motor )**

I have a 13sp and brand new RS404 3.70s cost was 6,000 installed.

running 60-70 rpms are 65mph around 1500 70 around 1600 and so forth.

Rounded_nut · 07-07-2019, **(Subject: CHanging rear end, paccar motor )**

Engine seems happy enough cruising there?

Lonestar10 · 07-07-2019, **(Subject: CHanging rear end, paccar motor )**

engine runs great in that area. granted its a cummins not a paccar.

Rawze · 07-08-2019, **(Subject: CHanging rear end, paccar motor )**

(07-07-2019 )Rounded_nut Wrote: Engine seems happy enough cruising there?

http://rawze.com/forums/showthread.php?t...3#pid13433

and...

http://rawze.com/forums/showthread.php?t...8#pid24378

Rounded_nut · 07-09-2019, **(Subject: CHanging rear end, paccar motor )**

(07-08-2019 )Rawze Wrote:
(07-07-2019 )Rounded_nut Wrote: Engine seems happy enough cruising there?

http://rawze.com/forums/showthread.php?t...3#pid13433

and...

http://rawze.com/forums/showthread.php?t...8#pid24378

Thanks for the links, been awhile since I read those. My only concern, and it's from ignorance, is at what rpm do I need to be concerned about valve float or damaging the pushrods, I want to say redline is 2200 rpm on the mx13 and I have no desire to say hello to a new window!

flatbed94kid · 07-09-2019, **(Subject: CHanging rear end, paccar motor )**

lonestar how are you liking your new rears? is it pulling better? mpg?

I hear some guy on hear got his from a salvage yard I think, like $1500?
yea way less but how big of a job is changing out the rears?

My thinking is you need to have new "U" bolts made and at a strength to hold the axles
good and tight. I bet some special or 2 different bottle jacks or axle lift. I just wonder why about almost every other truck passes me up climbing the mountains, even if I am light weight it just seems my truck doesn't have the power. But yes I am not giving it a hard foot. Rawze, the way you drive, are you slower then most others in the hills?

The newer trucks are geared like high, like 2.47 or whatever. I bet they are all geared like that passing me. Is it the new automatic transmissions why they pulling better?