RPM's and 5th Gear Nut?

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I just got back from a trip pulling my fifth wheel. I lost the fifth gear nut a while back and am now paranoid about lugging or pulling hard in fifth.
The mechanic (a diesel head)that fixed it told me to drive faster and keep the rpms above 2k or so and I shouldn't have more problems. I really don't want to pull the trailer this fast as I'm probably over loaded, well, yeah, I am over loaded.
Now I'm backing off on hills at 70 mph, when I have plenty of power left, so I can pull hard in 4th. I'm jockying with 18 wheelers that I could blow by in fifth.
Question for other paranoids:
Do you drive "special" after loosing the nut? If so, what precautions do you take? What rpm's are safest?
My wife says to go ahead and spring the bucks for a US Gear over so I can relax in 4th gear over. Anyone go this route?
Thanks... ... . Paranoid Ron

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'99 Quad long bed, 4x4, 5 speed, 3. 55 limslip, DD stage IIs/boost module and elbow, US Gear D-brake, Mag-Hytec, 4" exhaust, gauges, stock filter, air bags and a bunch of other stuff. Pull a 30' Wildwood
fifth wheel.

 

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Ron, knock on wood, I haven't lost 5th yet. However I read in the TDR way back in a early issue that if RPM's were keep above 1750 or so, 5th was less likely to back off. Also, not to work it hard in 5th. I've been following this advise for the last 40k, and I'm at 65k now. I'm going to do the fix before heading to the Rockies this fall hunting. I'll sleep better just knowing I've made the repair.

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"95" 3500, 4WHD, Ext cab. SLT, 5 spd, 4. 10 LSD, Rancho 9000's PacBrake, running boards, Mopar mud flaps, Isspro EGT, 50lb. boost, TST #8, no cat, muff or turbo ring.

 

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Hi Ron:
Lost nut last time at 122,000. Now I have 168,000, pull a 11,000 fifth-wheel in fifth gear and sometimes in fifth-over with the US Gear overdrive. Don't tell uncle Clinton but I have had it over 80 in five-over on flat land. But that is to fast even for me. The nut has spun off 3 times. So far so good. I don't baby the truck because of the nut but rarely turn over 2200. One thing I was told not to do that I don't do is lug the engine.
Good luck with your transmission.
Preston

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96 3500 Black 5 speed turbo diesel, SLT, with US Gear overdrive, Rhino liner, Reese 15,000 lb. fifth wheel hitch, US Gear de-celarator exhaust brake, muffler elimination kit, Amsoil lub. , with other goodys on the way.

 

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Couldn't you just replace with a 6spd?
How about a 9spd from a truck?
Ericson Truck Salvage sells alot of used truck trannys... . lots of options there.

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'97 FL60,5. 9 cummins,marine pistons(15. 0:1compression ratio),thicker head gasket,300hp. diamond"b" injectors,HX40-16cm2 turbo,custom grind fuel plate,4"straight exhaust,no grid heater,44psi of pure pleasure!!!!!!!!!!!!!
<<>>Charles Pyatt<<>>
CATERPILLAR... yeah, they do move pretty slow!!

 

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Ron ,don't know if you are a new member or have ever seen my post on 5th gear fix-but you have only a few options. how much money do you want to spend-including a nother conponent to maintain,when loaded (in box) or towing it will shorten the time it takes for the nut to back off.
what will extend the milage is if you bought a 5 spd and run in 4th every time you see a rise in the road that will drop the rpm's from the (fuel burning)range down into the
torque(pulling power)range (1750 & down to about 1600) the point where you feel the power kick in.
I drop in to 5 th loaded or empty around 1450
1500. and most of the time never wind it above 2100-2200 unless i'm climbing a steep hill or running 70 . i have a 4:10 rear.
been as heavy as 32+ and pulling the hills of NC-VA-W. VA going past the big rig's like
i was empty with the cruise set,except when the outside temp is above 90+ and humitdy is
is up there also.
I considered the gear vendor& u. s. gear long before i lost the nut at 32k miles but when i happened across a couple of guys that carried the factory rear cover and oem. drive shaft with them that told me mpg gain/cost + maintance was not going to stay off some failure in the drive train.
So i went with 235's for mpg's improvement-would have installed 390 gears but we only have 4:10-3:54's.
The trouble with an over-drive transmission is the high speed rev when trying to back a heavy load up an incline,another reason for 410. saves on burnt clutch linning.
And i like you bought a 5 spd for the fuel mpg.
Having been a diesel mech/shop foreman/sev. &parts manger-maintance dir. over the coarse of 25 yrs at the same location and was into elect. eng. controls back at the start in 83,(factory production) have been around the block. 125 power units and 200+ trailers.
As i told the head guru my only intent was to cure the "issue"(mfg. lingo) for a
problem,( ram's& GM diesel powered units) and at the low cost to owner /mfg.
Tried there 4th attempt at a fix (current split -clamping nut ) held under normal use (from date of purchase) 49K (which loaded miles was about 70 % ) -(oem nut miles were 32k @ 50% loaded miles/with 2nd try to fix losted nut issue.
In a nut shell--- go with the third (3 rd) fix nut and new 5Th gear (if old gear can be slid off & on by hand)BUT I CAN SAY HERE I REUSED THE GEAR AT 32KAND A FLAT FACED NUT AND IT HELD FOR 260K+.
Dis-reguard the need to replace the main shaft(at this fix they cut a key way into the shaft and had you stake the nut into the key-way(didn't work ,but was close).
****Instead use the supercided current(split) production nut,( New Venture # may be 1875) follow there instaltion steps
with lock-tite on the shaft and nut and stake with a min. SNAP-ON or THE LIKE 3/16 PPCA CENTER PUNCH & with the use of a 2-3 lb HAMMER around the dia. of the castle/flang
type nut. *****"" in short put you back in-to it,when i fix anything it may not be fast but it is my intent to be the last that is needed.
if you are paying the other guy to do the work should only take 3-1/2hr. with a coke break-w/pizza.
transmission modifacation can be done with out being removed,add 1 hr if 4x4. Questions call
219-936-9844 nut cost -$20. 00 w/o ship
order from 1-800-std-tran
internet - www.standardtransimission.com ???

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96-3500 SLT EXT. CAB AM/FM/CD-RINO LINER. D-CELERATOR EXH. BRK-RED LINE VAC. OVER HYD BRK CONTROL- AIR BAGS W/HVY DUTY AIR COMP. PUTCO S/STEEL DEEPBOARDS FRONT TO REAR. REESE 20K 5TH WHEEL & GOOSE -REESE 20K HITCH BELOW W/17K RECEVER. CLEAR COATED & SOUND DEADINGING &UNDER COATED 5 SPD/W 4:10 MCHLN'S 235/16'S UNIDEN PC76/WEATHER-WILSON 1000 MAG MOUNT ANT. 4 WHL ANTI LOC BRK SYS.

 

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Thanks a bunch tdrmember, Joe Donnelly and all members for having patience with me and giving me so much info on this damn 5th gear nut problem and gear splitters! I decided against a gear splitter and to go for the fully splined shaft from www.nationaltransmission.com
The kit contains the splined shaft and a new 5th gear for $459. 98. The new nut is $27. 12. If I don't need the gear I can send it back. I believe the shaft alone is around $200 but am not sure.
The guy I talked to says they see a bunch of these gears that have come off and ruined the spline on the main shaft. When the nut is on proper the gear only covers 1/3 of the shaft. If the nut just pops it threads, the gear can slide off the splines creating a new neutral. If the nut backs off, the gear can run on even less spline and both gear and spline can get mangled.
The transmission has to come out for the installation of the main shaft, but the main cluster doesn't (for you guys who understand this transmission talk). They charge $175 to do it with the transmission removed.
As they are in Texas and I'm in Nevada maybe I can get Joe Donnelly and/or his main transmission man, Craig, to help me do it, or do it for me. transmission work is a little over my head.
How about it Joe? Want some more experience? he he #ad

Anyhow I thought I would pass this along... ...
Thanks again,
Ron

 

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Hey, Ron
Did I hear you say something about buying me a kit if I get yours done? hehehe
I think you are doing the right thing as long as their shaft is equal or better strength than OEM.

 

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Hey Tdrmbramr,
what do you think would be the better way to go with Standard Transmission: (1) get their main shaft upgrade with the 5th gear and nut $470+ or (2) go for the rebuild NV4500 with the 5th fix for $1600 + core ($400)? I've got 90K+ now and pull 8K+ dump trailer weekly and am getting very paranoid ever since hearing about this problem.


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1997 2500 ST 4x4, 5-speed, 4. 10 axle, TST 60lb boost @ EGT gauges

 

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As far as a new main shaft with longer 5'th gear splines will it cure the loss of the nut??????????????????????????
back in 96 and then when i tested the new split nut the head guru at n/v said they didn't know which came first (chicken/egg) ie. nut comming loose letting gear vib on the spline's or the other way around.
In my experance ,the first time i reused the 5'th gear, which i slid on and off by hand and the flat faced approx 3/8 thick nut staked 8 times and held 260k + . With
the split nut test with new main shaft ,5 th gear and new 5'th idler for a fair test and a failure i again used the now used 5 th gear and the 3rd fix nut (now superceeded by split nut) staked with a center punch aprox 15 times and still holding after 330k+ and knowing the loads i've pulled over those knobs in the roads ,would i spend the extra $$ ????????????
I think i know which comes first. Will get back to you if it ever comes loose.
Be safe . Have a safe ride.

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96-3500 SLT EXT. CAB AM/FM/CD-RINO LINER. D-CELERATOR EXH. BRK-RED LINE VAC. OVER HYD BRK CONTROL- AIR BAGS W/HVY DUTY AIR COMP. PUTCO S/STEEL DEEPBOARDS FRONT TO REAR. REESE 20K 5TH WHEEL & GOOSE -REESE 20K HITCH BELOW W/17K RECEVER. CLEAR COATED & SOUND DEADINGING &UNDER COATED 5 SPD/W 4:10 MCHLN'S 235/16'S UNIDEN PC76/WEATHER-WILSON 1000 MAG MOUNT ANT. 4 WHL ANTI LOC BRK SYS.

 

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With 330,000 miles on fifth gear, it surely sounds like tdrmember has got it down! It seems to me a new fully splined shaft, new fifth gear and staking the nut down would be about as much as a guy could do.

Joe,
I'm going to keep the shaft, gear and nut in my goody bag as an insurance policy and drive the truck as if there is no fifth gear problem. I will see how long Craig's fix holds up. If the gear shifter starts any vibration I will consider doing the job.
If you or a friend need it, give me a call.
Ron