Loss of power and shuddering when hot

[HardCorps79]

Loss of power and shuddering- it was the U-joint!

So after a week of lovely in-town driving, I took the M1009 out on the freeway and the evil shuddering came back. It does fine accelerating and shifting in town, and is good for about 15-20 minutes on the freeway, but after that it gets weird:

At high RPMs in 2nd gear and low RPMs in 3rd (40-60mph), it shudders like an off-kilter washing machine on a spin-cycle, both accelerating and decelerating, and feels sluggish with both speeding up and slowing down. Then if I come to a stop, it does the same sluggish, low-power, shaking and struggling to get over 40 mph. Once I get over 65mph it stabilizes.

If I let the truck cool down for a good hour or two, it runs just fine again.

It will run in-town all day with no problems doing 55 for 20-30 minutes, getting to 65 for short periods, but over 60mph for 20 minutes and it gets stupid. What gives?

I know I need to change the transmission fluid/filter, and am probably due for another oil/filter change and fuel filter (been about 3,000 miles), but this seems to be a beast of a different nature.

Time for a tranny rebuild? New transmission oil-cooler lines? Harmonic balancer? Vacuum pump? Sticking governor? Fuel delivery problem? I really am at a loss here. Any advice would be great.

 

[4bogginchevys]

does it smell hot.......
is it full of coolant and burped too?
does it do this regardless of how full gas tank is?

figured it's somewhere to start anyhow

 

[HardCorps79]

-It doesn't smell hot, but there's a bit of tranny fluid sort of condensed on the bottom of the pan. Doesn't seem to be leaking much though, as the level hasn't dropped. Not sure where the fluid is coming from though. Also, should the rear drive shaft be slightly slick looking at the back of the tranny? Mine is. Hadn't noticed this before.

-Coolant is full. What is this "burped" of which you speak?

-It does this whether full or below half (really don't let it get below 1/4).

 

[4bogginchevys]

I cant speak for all trucks but my 1008 has the upper radiator hose higher than the fill point so you can never get all the air out of the system, it can cause it to over heat. problem is fixable with a funnel from napa(kit comes with 3 different rad caps/funnel) PN/77-4000. I just bought one and burped mine

 

[HardCorps79]

Okay, so I apparently do have a coolant leak I had somehow missed before. Went out today and the coolant had leaked on the driveway and was about a quart low (guesstimating). Seemed to be coming from around the bottom of the radiator on the driver side where the tranny coolant lines go in. Assuming *hoping!* that this is the issue with the truck and it's the tranny getting hot. Also noticed a fair amount of fluid on the undercarriage around the transmission. It's pretty dirty so it was hard to tell if it was coolant or tranny fluid. I'll check the levels again in an hour and report back. Really wish these problems would hold off until January... (raise and bonus coming in).

(Wouldn't it be cool if I could drop in a refurb crate engine, factory reman'd tranny, and a fresh IP!- Only about $2-3k)

 

[HardCorps79]

BTW- where would I get new lines to run from the radiator to the transmission? Is it a specific part, pre-bent, or can I upgrade to flex lines, what type of fittings? Anyone with a quick answer? (I know I could research, and I will if no one knows off the top of their head, just throwing it out there for recommendations...)

 

[blzrgb]

On the Blazer in my avitar I used small Hydraulic lines. My local CarQuest crimped the ends on for me. Works real good and much easier to install than hard lines.

 

[HardCorps79]

On the Blazer in my avitar I used small Hydraulic lines. My local CarQuest crimped the ends on for me. Works real good and much easier to install than hard lines.

Thanks. Do you remember the size of lines, lengths and fittings?

Not sure this will solve my tranny problem, but it's a starting place. Something to maybe keep me on the road a bit longer. I've had problems that seemed like $100+ issues end up being a $.05 fuse or length of wire. Hoping this will help. Can't hurt.

Anyone else got any ideas?

 

[blzrgb]

I don't remember the size, but what I done was take one off and carry the line with me and we matched it up at the store. Also, I put 45 degree fittings on the trans end of the hoses.

 

[acesneights1]

Are you sure it's a tranny problem ? sounds like a dead IP from what you are describing. Is there any grey smoke when it's running like crap ? Does it do it if you stop or does it idle normally ? Also if you suspect tranny how dos the fluid look burnt ? smelly ? If it's chattering then that could be the clutch packs wiped,time for a rebuild but it's shaking and running like it's missing and smoking try pullling over and pouring water on the IP and see if it clears up.

 

[HardCorps79]

Well, it turns out it wasn't the tranny or the IP or anything else I'd surmised. Found at 70mph an hour from home and an hour from my holiday destination that it was the rear U-joint!

Truck started shaking to the point I couldn't see the numbers on the speedo, and then it sounded like all **** broke loose. Pulled over to the shoulder and saw my drive shaft hanging down. Sure enough, the U-joint had blown apart. It was the end caps on the yoke that blew out and the drive shaft dropped.

Got it towed courtesy of GEICO roadside assistance to a dealership 15 minutes from my folks house. Dad came and loaded us all up and took us home for Thanksgiving. Went out today and replaced the U-joint (heavy duty part with lifetime warranty was just over $15 or so). Rented the U-joint/Ball-joint press for a $120 refundable deposit to make the job go quicker. Having never done it, the job took about an hour- mostly just figuring out what we were doing.

I'd say now that I know how to do it, changing the U-joints should only take about 20-30 minutes or so. Took the truck out and it was driving great- no shudder to speak of, and full power up to 75 (I don't go any faster than that in any vehicle usually). Seems the issue is taken care of.

Still need to change my other fluids and get a handle on the coolant leak (seems the top driver side hose leaks between 40-50 degrees outside, but no other time).

One other question:
-Lost probably a pint of tranny fluid out the back when I pulled the drive shaft out to realign it. Checked the levels and it seemed fine before and after a 20 minute drive. I'd accidentally overfilled it by about a pint before, so this makes sense. But, is there somewhere else I need to check the fluid level other than the one in the engine compartment? (This may be a really stupid question, but I have to ask). Always trying to cover all my bases, especially before I make the 150 mile trip home.

 

[4bogginchevys]

if I read this right than I would suggest checking the fluid level in the t-case.

 

[HardCorps79]

Good to go. I'll check that first thing tomorrow. If I read the TM (Lube Order) correctly:
If it's empty it should take 5.0 Qts full.
Full would be at a level 4" below the fill hole.
I've got an unopened gallon of Dex ATF in the back of the truck. Figuring I lost maybe a pint or a quart. Think I can handle it.