[ckucia]

This isn't a hotrod question, but there's so much knowledge and experience here, I thought I'd post anyway.

Have a 2000 GMC FS Sierra (1500) 4x4 pickup. When I pulled into work today and put it into reverse to back into a parking space, I heard a loud clunk and the trans started making a loud whirring noise. Won't go into reverse now. Makes the noise whenever the engine is running, and it increases with RPM - noise is louder if I put it into reverse.

It does go forward, although the noise remains (although fainter). I haven't driven it far, and don't know if it will upshift.

From what I've read, I probably cracked the sun gear or planetary case. I guess its a common problem on these transmissions.

Anyhow, I'm going to see what my options are. Just curious if anyone with experience has any other thoughts on what it might be.

Also, I've been inside a lot of engines. Dabbled in transmissions. Is this something I could rebuild myself? I have the factory service manuals and it looks like I can get all the parts from either GM or www.drivetrain.com. I'm patient and detail-oriented, but don't know what I'd be getting myself into. Are a lot of special skills and tools required to rebuild a trans and is it best left to experts, or is this something I could tackle if I took my time?

I can drive my "summer car" for now, so as much as I'd like to get the truck back on the road, I'm not in a big hurry.

[ckucia]

Also, while I have it out, would putting a shift kit (like Transgo) be worth it? Anything else I should consider doing/changing while I have it out.

Even if I have it rebuilt/replaced, I'll be taking it out and putting it back in myself.

[vicrod]

Before you decide if you are going to try the rebuild yourself, have a transmission shop evaluate the problem and price the job with the trans removed and reinstalled by you.

Try to find a shop that does hotrods and off-road work. And if they will give a
warranty.

The pros know how beef up the things so you don't have trouble in the future.

You may find that it's not worth the $ difference and hassle to try it yourself.

A shift kit is OK but not too aggressive.

vicrod

[Jmark]

I can't offer much help on what broke but I can say that if you inclined to rebuild it yourself, go for it. I did my first 350 last year and its doing fine. I now have a 4L60 apart and am going to be doing it next. All in all, it came apart quite easily, just follow the book and take pictures. You will need a spring compressor to remove all the apply pistons for re-sealing, but you can make your own or find a shop and ask them to do it for you, along with installing and re-sizing the input sealing rings. (not hard at all!)

As far as upgrades, you can get carried away. My plans for mine are a new HD sun shell, new sprags, Raybestos "Z" 3-4 clutch pack, .500 boost valve and better low/reverse valve, Corvette servo, HD band, new Torrengton bearing set and mild shift kit. I've priced all the parts from converter to tail housing seal and it will run me about $550 all together.

I ordered a CD off eBay that covers basic dis-assembly and re-assembly plus the ATSG book so I'm good to go. I've also ordered up the piston compressor and am thinking about buying the sealing ring installer/resizer too.

I just want to do it myself since all the years of shying away from trannies.

Mark

[Crosley]

IF the sun shell is broken , the tranny will NOT back up ( no reverse) .... it will NOT have 2nd gear or over drive (4th)

It is a common failure .


The tranny will shift 1 - 3

[ckucia]

Crosley,

I think you've nailed it. My grandmother's house (with a large enough garage to get the truck in) is only a couple of miles from work, so I drove it over there last night.

I didn't go fast enough to know if 4th is working, but 2nd is definitely gone as is reverse.

I was glad I had third. First is a little high-revving, even at 35mph.

Jmark/Vicrod,

Thanks for the advice.

I think, at minimum, I'm going to take it apart myself and see what the total damage is. Then I'll make a decision from there on what to do next.