Drive train problems

[jcasey007]

I'm trying to diognose a nasty noise from my drive train and need some advice. Please

The truck is a UK model 2nd generation V6 4WD Autobox 1997 with 90k miles

when cold all is nice a smooth, after 15-20 miles and warm, at low speeds there is a sort of clunk and judder which is road speed related. From stand still, creaping forward you can feel each lurch in the truck. In 4wd high, the clunk is less noticeable but when more torque is applied it does not sound healthy.

I'm not sure at this point if it is related to which gear it occurs more in because the quicker you drive the smoother it becomes until at 60+ you don't notice any vibration or juddering.

I've changed the rear axle, propshaft, the gearbox oil level is spot on and the colour is good

I guess my first question is autobox or transfer box? followed by has anybody see this before or got an idea.

Help is most apprciated

regards

Jim

 

[jcasey007]

so I've changed the transfer box as the output bearing was shot, It is a lot smoother and this has allowed me to understand the symptoms better.

The judder now occurs in second gear (but not all the time) by 30 mph it is smooth.

so this looks like the auto box,

so does anybody have a really good explanation of how the autobox works,

I've checked the sticky's but could not find what I needed.

mechanical or electrical?

cheers

 

[gijoecam]

so I've changed the transfer box as the output bearing was shot, It is a lot smoother and this has allowed me to understand the symptoms better.

The judder now occurs in second gear (but not all the time) by 30 mph it is smooth.

so this looks like the auto box,

so does anybody have a really good explanation of how the autobox works,

I've checked the sticky's but could not find what I needed.

mechanical or electrical?

cheers

The short version of how it works on your '95....

In 2wd mode, the transfer case is not operated, and the front axle's center axle disconnect 'breaks' the passenger side axle shaft. That allows (in theory) the front differential and driveshaft to stop turning. (I reality, due to the design of the transfer case, it doesn't completely stop at all times, it simply cannot transfer any power to the front end thanks to what is essentially a broken axle shaft)

When you shift to 4high, the system engages the center axle disconnect to lock in the front axle, essentially making it a live front axle. The system then monitors the front and rear axle speeds via the sensors on the transfer case to determine when wheel slippage is occurring. When the system determines the rear wheels are slipping, it engages the transfer case on-demand, varying the duty cycle of the transfer case clutch until the wheels are turning at the same speed again. It's essentially a rear-wheel-drive-until-the-rear-wheels-slip system. In 4low, it locks the transfer case in at 100% duty cycle as well as engaging the low range gearset for torque multiplication.

Simple enough??

-Joe

 

[jcasey007]

problem sorted !

I've tracked down my problem today so smiles all round !

my symptoms (worst first)
1. front wheel shakes better and worse at different road speeds
2. low speed grinds and clunks
3. constant virbation

so over the past 3 weeks i've replaced

the rear diff
the rear prop shaft
transfer box
and i was just abount to replace the Autobox tomorrow

as it happened I had a spare 1/2 hour today and a spare front prop shaft, i had checked the rear cv joint of the front prop shaft when I changed the transfer box and was ok.

when I dropped the front propshaft today i found that one of the uj cups was tight and dry. so 20 mins later the replacement is in and the difference is amazing

job done