need some help on a 98 k3500

[Streetgliderx]

well fellas i been over to FSC forum and i get CRAP, SQUAT, NADA, for help so i thought i may try you fellas......

here is my rig its a welding rig 98 K3500 chevy what i have been gettin is a bad "hop" when backing up on asphalt.... not as bad on dirt.....

i have replaced all motor mounts and trans mount.... no help...

replaced shocks with 9000 offroad shocks... no help...

replaced springs with a heavier set of USED springs from a higher load truck.... no help....

replaced clutch and had flywheel faced... no help...

not replaced but inspected u-joints and they seem fine no play or looseness


my guess is because i am constantly loaded (12,600lbs) i am getting axle wrap that is "pitching" my truck up... it just bounces up and down pretty violently when backing and its so horrible when hooked to a trailer you have to back up in 4LOW.... seems worse when hot, as in been drivin for an hr or so..... could it be wrap? will some ladder bars fix this? if so what kind do i need to build for a stock height, never gonna lift, and never gonna flex out truck?

last idea is a warpped drive shaft..... but would i not see a vibe at HWY speed?

thanks fellas!

 

[b454rat]

Hmm, don't think it's the springs since you replaced with heavier. Not the flywheel/clutch, so that's out. I wouldn't think its the joints or shaft, you would feel it going foward as well. Only thing left I can think of is the tranny, but don't see how a reverse gear could do that....

 

[toomany]

Does it feel like the brakes are dragging? The rears are supposed to self adjust when reversing. If they are sticking then in could make it seem like a hop.

 

[tourdog]

could be the reverse gear is to high does it hop in four low had a dodge truck always had hard time backing up really bad when hook to trailer just to high of gearalways had to use four low backing hated truck trade it try looking in to lower gear for reverse

 

[Streetgliderx]

Hmm, don't think it's the springs since you replaced with heavier. Not the flywheel/clutch, so that's out. I wouldn't think its the joints or shaft, you would feel it going foward as well. Only thing left I can think of is the tranny, but don't see how a reverse gear could do that....

it does it in forward too but not real bad at all..... and the springs were also used so they could have maybe been overloaded like my old ones were?

Does it feel like the brakes are dragging? The rears are supposed to self adjust when reversing. If they are sticking then in could make it seem like a hop.

just went over the rear brakes since my e-brake was all the way to the floor... seemed free and after adjusting them up the prob did not improve or get worse.....

could be the reverse gear is to high does it hop in four low had a dodge truck always had hard time backing up really bad when hook to trailer just to high of gearalways had to use four low backing hated truck trade it try looking in to lower gear for reverse

its got a small skip in 4lo but nothing like when in 2wd... its a 4.10 rear ratio... and it does seem alittle high sometimes while trying to manuver


one other thing i noticed today.... when at hwy speed and you roll out and then roll back on it real hard real quick it does the same cab shaking hop for a second then smooths out....

 

[DEMON44]

Pull and inspect the driveshaft closely. money is on ujoints or at least 1 ujoint. its a seized ujoint you'll be looking for not a loose one.

 

[Streetgliderx]

Pull and inspect the driveshaft closely. money is on ujoints or at least 1 ujoint. its a seized ujoint you'll be looking for not a loose one.

ahhhh never thought of that...... i have has small things cause large problems before..... and now that you mentioned that i had a tractor shaft bind up start shearing pins... i replaced alot of expensive stuff before i found out it was a frozen u-joint

 

[DEMON44]

whats the word?

 

[Streetgliderx]

well due to a job i got i been put off to work on it till this weekend but first i gonna swap u-joints then pull the rear diff cover.... my rear is the G80 and i also gonna change the fluids in the rear and trans

 

[4xcrazy]

you are describing what sounds to me like the same issues i used to deal with when i drove truck OTR, when you try to "feather" the clutch or short engagements for ultra slow movement at engine idle, while heavily loaded, it hops, bounces and jerks, especially when you've been working the trailer trying to get it in the dock and heating up the clutch

you mentioned it when you go forward too, sounds like some sort of clutch engagement problem or chatter of some kind, also like previously mentioned with the gearing.

 

[75GmcJimmy4x4]

what about the leaf spring bushings on the frame mounts ... not the rear ones with the shackles... ?? just a thought

 

[Streetgliderx]

you are describing what sounds to me like the same issues i used to deal with when i drove truck OTR, when you try to "feather" the clutch or short engagements for ultra slow movement at engine idle, while heavily loaded, it hops, bounces and jerks, especially when you've been working the trailer trying to get it in the dock and heating up the clutch

you mentioned it when you go forward too, sounds like some sort of clutch engagement problem or chatter of some kind, also like previously mentioned with the gearing.

well i had the clutch replaced with a newer "heavy duty" one but no change.....wonder bout the slave cylinder? i wanted to ask i been seein talk of a synchro mesh trans fluid mine might supposed to run.... but when the guy rebuilt the trans i have no idea what fluid he used.... will wrong fluids do this?

what about the leaf spring bushings on the frame mounts ... not the rear ones with the shackles... ?? just a thought

when i replaced the springs i put all new bushings in the rear set.... i had that suspicion too after one was kinda sticking out the side past the spring

 

[DEMON44]

No the wrong fluid won't do what you describe. regular gear oil will attack the fiber and brass syncos that the nv4500 uses. causeing the syncros to fail. grinding gears when you shift. not shuddering when engaged.

you need a GL-4 rated synthetic oil. standard gear oils are GL-5 even regular synthetic oils are GL-5.

this is part of an NV4500 3rd gear syncro.

change both your ujoints and I bet you your problem goes away.

 

[Streetgliderx]

alright fellas here is the update..... changed all fluids in all gear holding cavities used synchrotrol or some crap from the chevy shop and used the rear end oil they reccomend for the rear end with the additive... all looked good no abundance of shavings... swapped both u-joints...... problem still exists

did find a small nickle sized dent in the drive shaft but no one was open to check it for me... it didnt look bent using a 4ft level for strait edge.... now i got out in the parkin lot of the local walfart and did some simple manuvers to see bout it.... it still has a small hop in 4lo but not bad... still has all the hop in 2wd.....

thinkin bout goin back into the clutch.. i just replaced it not 10k miles ago at a local shop and it didnt affect it... but maybe they did something wrong??? i think i gonna build some ladder bars and see if that will help then i gonna have to throw money at it till fixed i guess..... just sucks cause i aint got abundance to throw

 

[DEMON44]

bummer. I thought for sure.........


OK then.
did it just start all of a sudden. or has it been gradual? get someone else to drive it slow like and make it do what it does....while you watch from the side. and pinpoint what the fark is going on. only when turning?? or straight? how about only in reverse? or in forward too? worse in 4hi? or better?

dont' build ladder bars. even if it fixes the problem, it will only be a mask. until the actual problem is discovered.

 

[Streetgliderx]

well i been watching it but i cant really tell... i see some axle wrap but i dunno if its enough to cause this..... its been a gradual thing and its strait or turnin, forward or backwards mostly in reverse..... its no better or worse in 4HI its gettin to the point i gettin mad!...... its mostly when lettin out on the clutch, this is the reason i spent 800 on a clutch install..... the rear main WAS leakin so i thought oil on clutch?... replaced that too... still no help..... is there a better stronger clutch for the nv4500? i may buy a strong one and replace it myself.... local shop claimed no aftermarket clutch upgrade avail??? but my dads 98 cummins dodge ate a clutch and he put in a button clutch... claimed stronger to handle the bad ass cummins he built for it... so far excellent results..... but aint the nv4500 in chrysler too?

thanks again guys for the help its been alot more than i got on a forum dedicated to these trucks.... go figure!!!!

 

[DEMON44]

theres major clutch upgrades for the dodge nv4500s. different inputs than the GM nv4500 those aren't compatible. South Bend Clutches and Valair are the 2 big ones I can thinkoff off the top of my head.

I'm sure you can get upgraded nv4500 GM clutches though. Luk gold I'm sure has one.



does it do it in 2wd? at all. i'm just trying to isolate components in my head.

this is the south bend Dual disk ceramic 3600 I had between my 24v and nv4500. uses a 1 1/4" 10 spline input shaft though.

 

[viperrgh2]

Could potentially be play in the rear end between gear mesh to gear mesh from a start...

 

[Streetgliderx]

while i had the drive shaft off and the rear diff cover off i used the redneck method to check backlash and it didnt seem bad at all... not near bad enough to cause this crow hop i been having......

 

[toomany]

Might the input shaft of the transmission be notched so that the disc doesn't move freely? Should have been checked when the clutch was replaced.

What kind of throw out bearing does it have? Dual mass flywheel?