6.4 hemi, 4.56 gears, speed and RPM's

[NewBlackDak]

Also, I'm Ret. LEO. I've been to 2 really nasty truck/trailer flip overs. REALLY NASTY. Once you see that, you will never tow 12k lbs at stupid speeds ever again. Short gears kinda act like a watch dog.

Not 1st, 2nd or 3rd? No Trophy!

I don’t care the weight. I’m not towing much over 60. I saw a blowout on a small utility trailer with a riding mower yank a half ton of the road to roll in a ditch. Fool passed me doing around 70 in a 55, and the blowout happened when he was about 80 yards in front of me.


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[[email protected]]

Ok guys just got my truck back from the shop.

The front they were able to use an AAM OEM 4.56 that is used for GM. The bearings were also changed.

The rear is a Nitro 4.56 all the reviews that i was able to find appeared that Nitro was better than Yukon. But what I think is funny they're made in the same plant in Korea or China. And by the AAM made in Mexico. Also all bearings changed.

Also replaced the front and rear diff cover with MagHytec. I only have like 20 miles on it gonna break it in and change the fluid at 1000 for both the front and rear.

So I spent 1900 for parts and labor at the shop and 560 on diff covers. Grand total 2460

Will keep everyone posted on RPMS , get up and go and towing

 

[RoadRamblerNJ]

Ok guys just got my truck back from the shop.

The front they were able to use an AAM OEM 4.56 that is used for GM. The bearings were also changed.

The rear is a Nitro 4.56 all the reviews that i was able to find appeared that Nitro was better than Yukon. But what I think is funny they're made in the same plant in Korea or China. And by the AAM made in Mexico. Also all bearings changed.

Also replaced the front and rear diff cover with MagHytec. I only have like 20 miles on it gonna break it in and change the fluid at 1000 for both the front and rear.

So I spent 1900 for parts and labor at the shop and 560 on diff covers. Grand total 2460

Will keep everyone posted on RPMS , get up and go and towing

We want 1/8th mile times and trap speeds! Old racer told me once "break it in like yur gonna drive it"

Not 1st, 2nd or 3rd? No Trophy!

 

[Obxram]

Very interested in your results. Please keep us posted

 

[smiley]

Update!

 

[RoadRamblerNJ]

Update!

Smiley, you *******! Seeing "Update!" under your picture just made me spit coffee on my phone. *****!

Not 1st, 2nd or 3rd? No Trophy!

 

[[email protected]]

I have about 200 miles now. The gears make a huge difference. I notice the biggest difference in my transmission and shifting.

At 70 75 staying around 2000 RPMS or lower 1800 1900. And like I said not shifting in and out of gears like before.

From a dead stop will spin the tires (37's) through 3 gear. It also hookups better and puts you in your seat when you don't floor it. But it is cold here in Michigan. Probably will be different in the summer because the tires will be warmer.

All in all I think they are bad ass. And once again thanks for all the help from everyone.

 

[tuffy]

Thanks for the update!
Have you towed anything with it yet?
I am still torn between 4.56 and 4.88 with my stock 33’s

 

[[email protected]]

Thanks for the update!
Have you towed anything with it yet?
I am still torn between 4.56 and 4.88 with my stock 33’s

No can't tow anything until 500 miles will keep you posted.

 

[tuffy]

Come on man go for a road trip and rack up the miles ... I can’t wait to hear!

 

[RoadRamblerNJ]

No can't tow anything until 500 miles will keep you posted.

88's bro 88's! It's only 1/3rd of a revolution more for your driveshaft to spin. 88's = more fun!

Not 1st, 2nd or 3rd? No Trophy!

 

[KarL45]

Well, my thoughts between 4.56 and 4.88 if going to tow heavy would today be the 4.88's. At first, with really no one changing to the 4.56 with the intent of towing heavy, wondered about the longevity of the gears as you will significantly reduce the ring to pinion tooth contact. Well, after 2 years of towing heavy and through many different elevations from below sea level to well over 10k, have literally no difference that I can detect in wear. That said, would recommend 12k mile fluid changes in the rear as have had the clutches start to bind on turns when it starts to get much over that on usage. Small price to pay I feel for maintenance. Only thought, if towing heavy and in the higher elevations on steep pulls, would recommend be vigilant about a quick, light decell when downshifting especially if getting into a higher gear and then trying to hold the load. Had it happen with the 3.73 where it got into 3rd,(easy to do if you can get the speed out of low as 10mph + 1000 rpm) so running it up to say 60 mph will allow it to shift to 3rd possibly and then when you accell harder to hold the load, will downshift into first. Had it spin the wheels and pull and break rivets out of the front of the 5'er paneling. Probably if that were to happen with ether 4.45 or 4.88 suspect severe drive train damage would occur. With exception of having to be careful there, thinking 4.88 would be optimal when towing. Probably put the 6.4 close to the diesel towing range. Any lower ratio though I think would not be very strong on the gear wear if towing and hauling heavy especially for extended periods. Just my thoughts

 

[RoadRamblerNJ]

Well, my thoughts between 4.56 and 4.88 if going to tow heavy would today be the 4.88's. At first, with really no one changing to the 4.56 with the intent of towing heavy, wondered about the longevity of the gears as you will significantly reduce the ring to pinion tooth contact. Well, after 2 years of towing heavy and through many different elevations from below sea level to well over 10k, have literally no difference that I can detect in wear. That said, would recommend 12k mile fluid changes in the rear as have had the clutches start to bind on turns when it starts to get much over that on usage. Small price to pay I feel for maintenance. Only thought, if towing heavy and in the higher elevations on steep pulls, would recommend be vigilant about a quick, light decell when downshifting especially if getting into a higher gear and then trying to hold the load. Had it happen with the 3.73 where it got into 3rd,(easy to do if you can get the speed out of low as 10mph + 1000 rpm) so running it up to say 60 mph will allow it to shift to 3rd possibly and then when you accell harder to hold the load, will downshift into first. Had it spin the wheels and pull and break rivets out of the front of the 5'er paneling. Probably if that were to happen with ether 4.45 or 4.88 suspect severe drive train damage would occur. With exception of having to be careful there, thinking 4.88 would be optimal when towing. Probably put the 6.4 close to the diesel towing range. Any lower ratio though I think would not be very strong on the gear wear if towing and hauling heavy especially for extended periods. Just my thoughts

All very good advice. Thank you for sharing your towing knowledge to us "less experienced" guys re: heavy towing. My one thought on the trans shifting from 3rd to 1st and causing damage with 3.73s is this...if you were running 4.56s or 4.88s, your trans probably wouldn't need to downshift from 3rd. All hypothetical on my part though. Looking to one day be towing heavy as I meander around the country with my wife. 3 or 4 years from now we hope. Thanks KarL45.


Not 1st, 2nd or 3rd? No Trophy!

 

[KarL45]

Ya, one would think with the 4.56 that that wouldn't happen, the severe downshift. It still can when towing heavy and trying to keep a speed without the high rpms. The probable cause of this issue is the computer for the transmission shift. If there was a tuner that could effectively let the engine pull more, say even 10%, without wanting to downshift, thinking the truck would be a better performer still. Also, watch your mpg indicator on a long and somewhat steep grade. Notice that when you are in a higher gear say 5th and running say 10 mpg, and unable to accelerate more without getting the downshift, that your MPG is probably 1 to 2 mpg better than when it finally downshifts to the next lower gear. And, with the 4.56, probably you will find when not towing that every time it down shifts, you have to let "out" of the throttle to maintain speed. It will increase otherwise. That said, love the truck with the 4.56 and wish it could be purchased through Ram with that gearing. The day they make it with an 8 speed, behind that engine and 4;10 gears, will put a whole new meaning to having a truck again. Probably never happen though.

 

[theviking]

FCA resources pretty much stated they were working on a new transmission for the HD's. Obviously it won't have less gears No details were provided but it's a pretty safe bet we'll see something new over the next few years.

 

[Ratket]

Good, my truck will be paid off and I can trade it in lol

 

[Brianedgestone]

I run 4.88's with mine on 35's and it's awesome! Although if I were to spend the money again I'd go 5.13. Mine are nitro gears as my truck was the Guinea Pig for them as the gas trucks use different pinion bearings unless u have the snowplow prep package and then it uses the same as the diesel trucks.

What are your rpms at hwy speeds? I’m deciding between 4.56 or 4.88. Have an appointment with the shop in April and still haven’t decided.

 

[U&A]

FCA resources pretty much stated they were working on a new transmission for the HD's. Obviously it won't have less gears No details were provided but it's a pretty safe bet we'll see something new over the next few years.

They are working on a 9 speed for the HD’s from what i was told.

 

[theviking]

They are working on a 9 speed for the HD’s from what i was told.

If they released a 6.4/9 speed even in the current gen HD I'd probably go trade my truck on a new PW tomorrow. That should be an epic combo.

 

[NewBlackDak]

If they released a 6.4/9 speed even in the current gen HD I'd probably go trade my truck on a new PW tomorrow. That should be an epic combo.

Assuming same capacities, I would be banging on the door for an SRW 3500 6.4 9spd.


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