Hi all,

Anyone have a whining noise while decelerating? All fluids, front differential, rear differential, transmission and transfer case fluids
have all been serviced and are full.

The only thing I can think of would be the speedometer cable?

Thank you

 

Will it only happen while moving or can you rev the engine in park and cause it as the engine returns to idle?

 

Hi Gumby, This only occurs when the truck its moving and I take my foot off the gas, decelerating or slowing the truck down for a stop
sign or a upcoming turn. It doesn't make noise while stopped and the engine is running.

 

I forgot to mention it in my first post but FYI your truck doesn’t have a speedometer cable - by 99 the cluster was fully electronic and using data from the PCM and other modules to control the gauges.

As to the noise, did you service the fluids in the diffs and TC? If so, were there any large (splinter size) pieces of metal in the rear diff? A whining/grinding on decel only that disappears when accelerating indicates incorrect backlash and/or end play between the drive pinion and ring gear, if indeed the noise is originating from the rear diff.

If there was large metal in the fluid, remove the cover and inspect the ring gear and pinion for chipped or cracked teeth - that’s unlikely the source unless the noise “pulsates” for lack of a better term.

The next step would be to get some gear marking compound and inspect the gear meshing pattern.

 

New news.....Several months ago I checked my Power Steering Fluid, it was at a normal level. 2 weeks ago I noticed stains on the street under the front end of my truck.
I had almost zero fluid in the reservoir. I replaced the pump, refilled the reservoir, bled the lines then drove around running some errands. The whining I spoke of originally has gone away, so my guess is the pump was on it's way out. I've never heard a bad PSP make THAT kind of noise before.

I came out of one store and there was a puddle under the truck. I checked the PSP fluid. It was normal. I drove home, but discovered my brake pedal would go to the floor but I could stop the truck. The next time I stepped on the brake peddle I had a solid pedal. This alternated for the next 4-5 miles. I made it home, parking in the street and let the truck sit for a while. No puddles. I checked the Brake fluid reservoir and found no changed in brake fluid levels.

I moved it one more time for the weekend. I checked it this morning, no puddles.


I'm really scratching my head on this one.

 

Remove the brake fluid reservoir cap and have a helper TAP on the brake pedal. They don’t have to press it all the way to the floor - the goal is to get the pistons in the MC to initiate movement, but it doesn’t have to complete a full stroke. While the helper is tapping on the pedal, use a flashlight to watch for a few air bubbles to rise to the surface of the fluid just as the piston begins moving in both sides of the reservoir.

Note that if the fluid in the MC is dark and unclear, it would be helpful to drain the reservoir using some kind of suction or siphoning device and flush the buildup out of the bottom using clean brake fluid and then siphoning it out again. I’ve seen so many of these trucks with sludge buildup in the reservoirs and sometimes they can’t be adequately tested because the buildup actually prevents the air bubbles from escaping.

If you don’t see air bubbles, the MC can no longer build pressure properly and should be replaced.

If air bubbles are present, look at the bottom of the MC where it bolts onto the hydro boost - if there’s significant fluid leakage present, it’s possible the MC or hydro boost is leaking. Note that a leak is marked by fluid actually dripping whereas seeping is marked by a damp appearance but has nothing actually dripping off.

 

Thank you Gumby, this was a huge help. I am getting air bubbles through the MC reservoir.

Odd that the fluid I found under the truck was a one time occurrence. I drove several miles yesterday with no fluid loss.

I do have a slight leak around the Hydro boost and MC. It's not significant or dripping, just messy. Is there a gasket between the two
units or is it a tight fit that prevents leakage? I need to clean it up a bit better to pin point exactly where it's coming from.

 

The seal between the MC and hydro boost is just a snug fit. You can’t see it without a mirror or removing the MC, but there’s a small drain channel on the bottom of the hydro boost because seeping from the MC and hydro boost is normal and the channel prevents the fluids from filling the gaps in between.

Don’t overlook the lines as sources of leaks, either. How long they last depends on use and care, but the crimps on the pressure lines usually start leaking between 50,000 - 80,000 miles. I’ve never seen them blow apart but unless replaced they’re a constant source of leaks.

The single puddle could have been fluid that was trapped inside the frame or on top of the skid plate or splash shield and finally drained out after a drive.

What I’d recommend is finding a pressure washer that has a hot water feed and adjustable pressure - some car washes have pressure adjustable guns in their manual bays. If you can’t find one, a garden hose off your kitchen sink will work too it just takes longer.

Use hot water and low pressure (soap/degreaser optional) to thoroughly clean the MC, booster, pump, gear box and lines. The gear box and pump are pretty easy to get at from the left front fender well, but if you’re running larger than stock tires it may not work. Also make sure to clean the PS cooler if equipped (usually a hydro boost has one). Remove and clean the splash shield, skid plate, and If you have factory tow hooks, blast some water through the frame channels as well.

Once clean, the source of a leak is usually easy to find, but there’s also leak tracer dyes available that can be used in PS fluid - I don’t know the cost (at work we buy it in bulk) but they’re sold in 1 oz bottles. 1/2 oz is more than enough for the PS system - the other 1/2 could be saved or used for chasing other leaks you might have.