No power in 5th Is this normal ?

[drebs17]

I have a 97’ cab and chassis 3500 standard trans 5.9 12v the truck has a metal flatbed so weighs in at 10,000 lbs

i was towing a bumper pull equip trailer with a 10,000 lbs forklift on it I imagine the trailer weighs 2,500-3,000 14 ft with steel deck

so gross I was at 23,000 lbs

when going from 4th to 5th after getting 4th up to 2,800 rpms and shifting to 5th around 68 mph I could and would not gain any speed in 5th with my foot to the floor on flat ground. Not losing speed but litterly couldn’t gain 1 mph.

 

[GAmes]

What was your fuel pressure, boost, and egt? Stock engine? 3.5 rear gears? Rpm at 68 mph in 5th?

 

[fest3er]

Also possibilities: dirty fuel filter, dirty air filter, pinhole allowing air to be sucked into fuel line.

Were you able to do so in the past?

 

[AH64ID]

If the motor is stock that sounds about right.

215/440 just isn’t a lot of power by today’s standards, and a GCW of 23K isn’t light. Using OD night not be possible except downhill.

There are some fairly cheap engine mods to get the power to come up quite a bit.

 

[drebs17]

Yeh stock engine.. well have replaced the fuel filter since, turned up the boost on the star wheel a bit to 30 psi wide open

I don’t know about back then didn’t have gauges then and haven’t hauled a load that heavy in a while but will be soon.

 

[RVTRKN]

Thats a clue you've reached your limit, however have you loaded it prior, with just as heavy or heavier? Also, did you weigh it or its a guess? Flat ground can be misleading at times, it may look flat, but it has an incline to it. When pulling my 5ver in sig, it seems like i'm flat road in the desert on I-40 or I-10 to and from Arizona, but the pedal confirms that I'm on an incline.

 

[DonFitzwater]

Yeh stock engine.. well have replaced the fuel filter since, turned up the boost on the star wheel a bit to 30 psi wide open

I don’t know about back then didn’t have gauges then and haven’t hauled a load that heavy in a while but will be soon.

I'm no pro on P7100's but the star wheel doesn't do jack for boost, only fueling when you jab the pedal down. If you want more boost, you've got to modify the AFC system. If you are getting 30 psi, it isn't stock.

 

[drebs17]

I'm no pro on P7100's but the star wheel doesn't do jack for boost, only fueling when you jab the pedal down. If you want more boost, you've got to modify the AFC system. If you are getting 30 psi, it isn't stock.

Ya me either the shop I take it to the guy used to be a diesel mechanic at the dodge dealership from 93-01 and said he gave the turbo or boost a “few clicks up”(there a star wheel on the afc that I’m assuming he was taking about but can’t be 100%?) for more
Boost and power. It had power in 1st- 4th gear just none in 5. Not that I need to be going faster than that, that heavy but as long as I’m above 1800 rpm (to avoid bandit off the 5th gear but) sometimes it’s nice to drop a gear on flat ground and not rev that high working the engine harder even though I knkw it can handle it , I’m assuming going 68 at 2850 rpm uses more gas than 68 at 2000 rpm.

 

[GAmes]

Of course going faster use more fuel, that's physics. 5th gear in the NV4500 is a weak link, and if you tow heavy a lot it will fail. Not just 5th gear, the countershaft, bearings and a couple other gears all fail close together.

 

[drebs17]

Of course going faster use more fuel, that's physics. 5th gear in the NV4500 is a weak link, and if you tow heavy a lot it will fail. Not just 5th gear, the countershaft, bearings and a couple other gears all fail close together.

I’ve heard that’s only if you lug below 1800 rpms from a lot of people..?

 

[RVTRKN]

You should never lug when heavy, your EGT's willl get out of control.

 

[drebs17]

You should never lug when heavy, your EGT's willl get out of control.

Right but I’ve heard you can tow in 5th AS LONG AS you stay above 1800 ... ideally 2000 ?

 

[RVTRKN]

Sweet spot is between 1800 and 2100 empty, heavy is 2100 to 2300. But that’s what I go by, I think it’s normal what you experienced.

 

[GAmes]

Right but I’ve heard you can tow in 5th AS LONG AS you stay above 1800 ... ideally 2000 ?

No one knows for sure what causes 5th gear to fall off, but that isn't my caution to you. 5th gear falling off is a minor inconvenience. I'm talking about catastrophic failure of 5th gear because of the heat generated. Keep towing heavy in 5th gear and one day you will be scooping pieces of gears and bearings out of the case.

 

[RVTRKN]

Heat generated towing heavy in 6th (G56) is why I developed my cooling system. I still pay attention to RPM's, and never allow my motor to bog down, no mater what gear it takes to maintain proper RPM for conditions. As the OP has experianced, his motor was telling him to downshift, regardless of his perception of a flat road. If the higher RPM helped him move the load in a lower gear, then more than likely his motor is OK.

 

[drebs17]

Heat generated towing heavy in 6th (G56) is why I developed my cooling system. I still pay attention to RPM's, and never allow my motor to bog down, no mater what gear it takes to maintain proper RPM for conditions. As the OP has experianced, his motor was telling him to downshift, regardless of his perception of a flat road. If the higher RPM helped him move the load in a lower gear, then more than likely his motor is OK.

Makes sense yes I have a trans temp gauge now and I have a fast cooler system (only 1 tho) as I have a pto winch on the other size. I run 6 qts with that setup, 1 extra for the one cooler then 1 extra through the shift tower and my pto gear box hold prob half a quart so I could even run 6-1/2.

At what temp in the transmission should I back off 5th and run 4th and at what time should I take caution in 4th?

 

[GAmes]

I had two Fast coolers on the 12 NV4500s I went through. For the first two or three I had a temp gauge installed. It was worthless for warning me of failure. I tried the extra oil too, No discernible benefit there either. 4th gear is direct, the only gear that is direct to be precise. There shouldn't be a problem towing in 4th.

 

[RVTRKN]

I found the Fastcoolers worthless, my trany, at a qt over and added oil for both Fastcoolers could easily hit 250* with only 15K lbs at GCW. Not until I installed a pump, filter and heat exchanger can I keep my temps @ 170/180*. As the picture shows, I tapped in 3/8 NPT threads at the bottom of the Fastcoolers. I have bought some 3/8 welding bungs that I'm going to weld on the OEM PTO covers and remove the Fastcoolers, as their no longer needed.

 

[drebs17]

I found the Fastcoolers worthless, my trany, at a qt over and added oil for both Fastcoolers could easily hit 250* with only 15K lbs at GCW. Not until I installed a pump, filter and heat exchanger can I keep my temps @ 170/180*. As the picture shows, I tapped in 3/8 NPT threads at the bottom of the Fastcoolers. I have bought some 3/8 welding bungs that I'm going to weld on the OEM PTO covers and remove the Fastcoolers, as their no longer needed.

Is that on an auto or manual? I’ve heard you can’t run a pump on manual idk why you couldn’t just always heard that. I’m on manual

 

[AH64ID]

G56 is a manual.

Tons of G56’s on the road without pumps/coolers and they last. Dad’s was at 160K when he sold it and it felt like new. Always had more power than stock and towed heavy.

The DMF is less than desirable, but the G56 has been a good transmission. It’s also the longest running manual trans for Dodge/Ram.