GM tech advice

[Ben824]

Ok so my little cousins who recently turned 16 just inheritited their family's 95Chevy Suburban 2500 HD 4wd auto and the 8.1L V8. Its got around 250,000 miles on it same engine and same trans I beleive. Well first I want to know if anyone knows these vehicles really well and if there is any common problems these things have that I should look out for? Also since it has so many miles on it I wanted to get everyone's opinion on if it would be a good idea or not to switch all the gear fluids (axles and t-case) to royal purple synthetic? I have no idea when the fluids were last changed and Im pretty sure there are just standard fluids in there because my uncle is kinda cheap haha. Same for the enigne oil? I would like to put this fluid in it because I put it in my 97 XJ 4x4 with 140,000 miles and it helped out a good bit I did notice a small increase in power from the engine and a little increase in MPG. Also any other advice on this vehicle would be greatly appreciated. These kids are on a budget so I would hate to see them put some money into it to make it cool and then have it break down on them.

[5-90]

Switching to synth fluids for the geartrain probably isn't a bad idea, but I wouldn't do it for the engine.

Synthetics tend to be rather more detergent than regular oils. Since the engine might have some sludge in it that's "boosting" a seal, switching to synthetic would clear that out and "cause" a leak (the synth oil doesn't cause the leak - but the switch does, because everything is suddenly clean. That's where the rumour comes from.)

If you're going to switch to synthetic in the engine, try doing so gradually. Synthetics also tend to soften seals, so a gradual change would both clean and soften the seals, and that would make it less likely for you to suddenly note a leak. Refresh my memory - how large is the sump on the 8.1L V8? I probably wouldn't change more than a third of the regular oil for synthetic at a time (take us, for instance. Six-quart sump, right? So, I'd do 4 regular/2 synth, 2 regular/4 synth, and then all synthetic after that. I've never had any trouble mixing synthetic and regular oils.)

Make sense? Since there isn't any pressure involved in the transfer case or the axles, it's not really a problem there. Transmission pressure tends to be "residual" - all the fluid has already done the work. So, probably half-and-half for the transitional change.

[Matthew Currie]

Look over the ball joints. By 95 they'd gotten past the amazing 10 thousand mile hidden-warrantee version, but they're still a weak spot I think.

16 year olds on a budget, and a 'burb with a 496 engine? It sounds like the perfect vehicle for parents who don't want their kids to stray too far from home. They're going to have to work hard to keep that thing fed.

[IXNAYXJ]

...'95 Chevy Suburban 2500 HD 4wd auto and the 8.1L V8.It should be either a 7.4/454 or 5.7/350. The 8.1 didn't come out until 2001, IIRC.

-----Matt-----

[Darky]

It should be either a 7.4/454 or 5.7/350. The 8.1 didn't come out until 2001, IIRC.

-----Matt-----
You are correct. That was the first thing to come to my mind. Its most likely the 7.4. The 8.1 came out at some point after Chevy started differentiating between HD and non-HD with the front end styling.

[Ben824]

oh ok well all my uncle said about it was that it had the "big" V8 in it so i assumed it was the 8.1L but still 7.4L is still a huge engine. i dont know chevy that well because frankly i just dont like chevy im a mopar man myself but i want to help my little cousins out and fix it up.