I stop for the light, then take my foot off the brake and start to
accelerate. Almost feels like someone bumping me from behind. Doesn't happen every time though. Any feedback would be greatly appreciated. :)

Sounds like trans slip check fluid and see if low or looks or smells burnt.

I would look at the slip yoke. Grease the splines and the clunk goes away.

What year truck, and how many miles?

I would look at the slip yoke. Grease the splines and the clunk goes away.

What year truck, and how many miles?


I would do this first, it is usually it.

And It is free!

What year truck?

How much fuel in the tank?
I've noticed this bump both accelerating and braking in forward and reverse with half a tank of fuel.

I stop for the light, then take my foot off the brake and start to
accelerate. Almost feels like someone bumping me from behind. Doesn't happen every time though. Any feedback would be greatly appreciated. :)

Stick Slip... Grease your yoke in your driveshaft. Mine did the exact same thing. I used Mobil 1 red synthetic grease. Not too much.. ;)

[quote=BudTX;2454130]I would look at the slip yoke. Grease the splines and the clunk goes away.

Anyone add a zurk to this area?

I would look at the slip yoke. Grease the splines and the clunk goes away.

What year truck, and how many miles?

I just did mine a month or so ago. Clunking when I took off from a light.

The grease GM uses is junk and the rear end slip yoke will be bone dry. Drop the driveshaft and lube the piss out of it and it'll be gone.

This has been a problem thats plagued GM trucks for years.

will this clunk happen when you come to a stop as well? Mine clunks when your almost at a stop just as the rear end drops, it clunks, after you hit the brakes hard. Same Solution???

I'm going to guess yes but I want to be sure.

Same thing.

Well I had to change a rear diff. u-joint about 3 mos ago, and I know that the slip yoke was well lubed when I took it off & I even lubed it again when I put it back on. My truck does the same thing on occasion, it actually feels like the tranny slips momentarily then kicks in when you rev it a little, not a typical dry thump at all, it acts just like the tranny is low & it takes a little rpm to get it to respond. Any ideas?

I'm going to guess that this is a 2001 like nmband13's.

My first suggestion is to check and see if the TCM software is up to date. There was an update way back that had to do with the 2-1 downshift and the symptoms were consistent with what I am hearing here.

Thanks for all the great input! Dropped the driveline and cleaned up the yoke and lubed the splines. Problem is gone! This is great, i love easy fixes. Anyone on how to fix a sending unit? Thanks again, the wife thinks i am a genius!:D

My truck is a 02 DMAX 6.6 Ext cab long box with Alli

I just love the easy fixes as well!

Are you sure it is the sending unit? And not the stepper motor?

M y speedo reads 100 MPH at 40, and the oil pressure pegs the needle, I have the get a couple of stepper motors and fix these.......

I just love the easy fixes as well!

Are you sure it is the sending unit? And not the stepper motor?

M y speedo reads 100 MPH at 40, and the oil pressure pegs the needle, I have the get a couple of stepper motors and fix these.......
The only thing on the guage cluster that is fouling up is the fuel gauge. nothing else is erratic. Talked to a guy that rebuilds sending units and this is a common thing with the sending unit.

This clunk is normal especially after dropping driveshaft. As stated above, drop driveshaft and lube the piss out of yolk with hi-temp grease, it may help, but probably not. The clunk is annoying but not damaging

The only thing on the guage cluster that is fouling up is the fuel gauge. nothing else is erratic. Talked to a guy that rebuilds sending units and this is a common thing with the sending unit.


Each gauge has a stepper motor, and mine started with the speedo, now the oil pressure is going, so one day I will get them replaced, most likely will do it myself, they are only 9 bucks apiece, and I have more time than money, so I will eat the labor..................

Thank goodness for my Scan Gauge!!!!!!!!! It reads off of the ECM, and stays pluged into the OBD II Port, it is a neat thing to have!

Is this a problem with every year truck? The slip yoke that is. Could this be the thump I am feeling in my 07 when I leave the light?
Thanks

After reading the replies again im sure thats what it is. I only have 9K on the truck.
I thought it was ice under the truck.
I was blind but now I see.

The only thing on the guage cluster that is fouling up is the fuel gauge. nothing else is erratic. Talked to a guy that rebuilds sending units and this is a common thing with the sending unit.
Your '02 has a different gauge cluster than the problematic '03 and newer trucks. The stepper motors aren't your problem. The sender in the tank is worn out, as it is a poor design. Since diesels have no in-tank pump, it should be less expensive. GM does sell the sender only, without the whole module assy.

Each gauge has a stepper motor, and mine started with the speedo, now the oil pressure is going, so one day I will get them replaced, most likely will do it myself, they are only 9 bucks apiece, and I have more time than money, so I will eat the labor..................

Thank goodness for my Scan Gauge!!!!!!!!! It reads off of the ECM, and stays pluged into the OBD II Port, it is a neat thing to have!
'02s are different. The problem you have is an '03 or newer problem.

Yea, I knew that, I just did not read what year his truck was.......:o:

Is this a problem with every year truck? The slip yoke that is. Could this be the thump I am feeling in my 07 when I leave the light?
Thanks


Could be

The slip yoke is usually pretty dry. You have NOTHING to lose trying it.

Talked to the service dept today and he said they have seen alot of these and said to bring it in because they may need to change it with a new stronger slip yoke made of diffrent material than the old one. Does this sound right to you?

Also we talked about the steering shaft and leaking hydroboost lines, he told me GM does'nt make anything yet that works for bolth fixes. He said to use the lines until they wont take no more and the steering shaft might feel strange but it isnt hurting anything.

I geuss I will fix the shaft from the ideas from DP.

My trucks had that thump 4 a year & a half! Cant figure it out. Thought it was driveline slop. I will grease this weekend.

Talked to the service dept today and he said they have seen alot of these and said to bring it in because they may need to change it with a new stronger slip yoke made of diffrent material than the old one. Does this sound right to you?

Also we talked about the steering shaft and leaking hydroboost lines, he told me GM does'nt make anything yet that works for bolth fixes. He said to use the lines until they wont take no more and the steering shaft might feel strange but it isnt hurting anything.

I geuss I will fix the shaft from the ideas from DP.

The new slip yoke will not fix it for good either, Maybe. So have them replace it, and if it comes back, just lube the crap out of it yourself.
The "new" yoke is made of a different material, and still is not a cure all.....:(

Will do. Thanks all!
Kyle

Stick Slip... Grease your yoke in your driveshaft. Mine did the exact same thing. I used Mobil 1 red synthetic grease. Not too much.. ;)

x2

I just greased mine and problem gone. GM has a TSB on this problem for the gas trucks and their fix is replacement of the driveshaft and slip yoke.

Craig