[JBenjaminhasaGMC]

Hey all, love the site. Always been my first source for Silverado related questions. That said..

I have a 2003 Z71(4.8l) with ~135,000 and it's been relatively poorly maintained due mostly to lack of funds. I absolutely love the truck and would like to get another 135k out of it. Recently I've cleaned the TBI(my idle was extremely low and occasionally stalling), new battery, and new OEM air filter. The oil & oil filter are also relatively new(I swapped over to non synthetic at ~100,00). I had the starter tested recently and it was perfect. I'd say nearly 100,000 of these miles were highway miles.

The truck's in desperate need of rear struts/shock absorbers which I am hoping to purchase and install ASAP(any suggestions here)? My ride's took an awful turn for the worse and it's getting a bit jumpy going around turns with even the smallest of potholes/et cetera.

Besides this, what should get immediate action? I'm thinking transmission oil and transmission oil filter and new oil in both pumpkins.

I'd love some feedback or links. I did a bit of googling but didn't find any great resources for long-term maintenance like this.

What's the general consensus here about seafoam? Go for it? Given the somewhat high miles on this, is there a possibilty I'll hurt it? It appears that I still have great compression on the cylinders, but I buried my foot in it recently after the new battery and cleaning the TBI and saw a good amount of sediment out of the exhaust.

 

[steverocks6]

well just out of curiosity, did u have synthetic in then go back to non-synthetic oil? if so id do a oil change asap and put synthetic back in. also with shocks just go cheap and get stock shocks really no point in making fancy if you just want this truck to last. also tranny filter and oil is always a good option, if you want your car to last last id change all fluids, tune up, ect. and as for seafoam i have a 2001 2500, it has the 6.0 in it and i seafoamed it with no bad results, just do seafoam about 100 miles before you change oil. also alot of engine life can be determined by how you drive, if you are nice to truck it will be nice to you.(they still do break though, they arent always nice back lol) just keep up with oil changes

 

[silveradotrailblazer]

Welcome to the club. Seafoam works very good. Check out there new spray can with a hose that you install in the throttlebody and spray while the truck is running. This cleans the intake manifold. Seafoam has several videos on there website that a very helpful. I WOULD do the trans and pumpkins for sure. If you change your spark plugs use A/C Delco's!! For shocks it depends on your budget, I like Bilsteins, Edelbrock or KYB's.

 

[TELORVEHC]

Switching over to all synthetic fluids (engine, differentials, transmission) will increase the longevity of those components and help make your truck last longer. X2 on the recommendations for Seafoam and the shocks. New shocks will help give your truck better road manners and will also help to eliminate some of that jumpiness.

 

[JBenjaminhasaGMC]

Thank you everyone for the feedback. To steverocks6 yes I was running synthetic until nearly 100,000 and switched over. I'm an old school guy and for better or worse, that's what has been instilled in me. I've been running nonsynthetic for nearly 30k now, does anyone have feedback on what would be the appropriate action here(I.E keep running non synthetic or switch back to synth.?). Shocks are definitely my first priority, this truck is handling terribly. If and when I do this, is there anything I should look for underneath it, specifically dealing with the suspension(like rubber bushings that have deteriorated)? I already plan on getting underneath it, wirebrushing all the rust spots and giving it a healthy coat of primer or spray on Plasti-Kote bed liner.

Once again thanks for the warm welcome guys and I greatly appreciate the feedback. To be honest this is for my fathers truck; I would consider myself a car guy but have absolutely no experience with these 4.8's or their chassis. Considering the small amount of work my father has put into this truck, I'm honestly surprised how well it's doing.

Basically I'm going to replace the shocks, check plugs & wires for proper spacing and amprage, wirebrush and prime the surface rust on the frame/body/what-have-you, and seafoam it.

I'd love more feedback. Thanks again all.

edit: TELORVEHC sorry if it seemed like I disregarded your suggestions. So the general consensus is it would be better to run all synth in everything? Seafoam and shocks will take first priority, along with another proper cleaning of the TBI. I have given it a quick once over with a tooth brush and TBI cleaner but I've read it takes a couple times for a proper cleaning.

 

[dsfloyd]

Welcome to the club. gonna sound somewhat like a broken record, but definately do shocks and fluids first. I like the bilsteins but they are a little more pricey (I think they were the stockers on the z71, could be wrong though), can always check out the monroes they are a little cheaper. Switching out all the fluids is a good idea. I have all synthetics in mine but not necessary just get quality brands. Plugs and wires (use AC Delcos on the plugs). the new ones to put in are the iridiums (pre set gaps). Seafoam and cleaning of the intake, MAF (only use MAF cleaner on it). Keep us updated on how this improves things and definately ask more questions along the refurbishing path. there are lots of ideas and opinions on here, even when some opinions differ greatly the folks on here will do their best to point you in the right direction and help as much as possible.

 

[billnorman]

I have used Seafoam before oil changes and was amazed by the good results. You should read the factory owners manual to see what the factory recommends for intervals of change, and try to duplicate them at home. I wouold not use Seafoam unless I detected dirty oil or the results of it, like noisy lifters or clatter at start up.

 

[JBenjaminhasaGMC]

Thanks for the feedback, I definitely have a better idea on where to start now. I've cleaned the TBI, MAF sensor is a good suggestion, and I think I'll try Seafoam as well. I suspect the lifters are a little sticky; it doesn't knock at all but started when cold there sounds like there's some gunk in there. Thanks all and I appreciate the warm welcome.