Shopping for a 6.2 Burb

[DSM]

Looks like I found the best place for advice! Glad I discovered this group and hope to someday offer help but, in the meantime I'm searching for a Suburban due to needing something larger than my MB 300TD wagon.

I had a few questions regarding the best years that I should search for.

Did any of the 1/2t suburbans get the "J" code?
What are 'realistic' fuel mileage figures?
Any particular models to stay away from?

Thanks in advance.

Dan

[DSM]

BTW, I'm not a stranger to diesels. Been working on '617' MBs for 15 yrs plus I have a 8.2 "Fuel Pincher" in an old farm truck a Cumins 5.9 and a couple of Perkins D152 powered tractors.
I Pop test and balance my own injectors as well as all other required repairs.

Just not familiar with the 6.2, 6.5 engines. Only that they got a bad rap from the 5.7 released earlier.
I've heard rumors of main web cracks and frequent IP failures. Those are the areas I fear.
I wont be towing with it so I'm not to concerned about the low hp/tq figures. As long as it can pull itself at hwy speeds with a 3.08 diff without overheating. Mainly looking at a large vehicle with a 3rd row seat and decent mpg figures.

[john8662]

The 89-91 Suburbans are the nicest, features wise.

No J series engines in 1/2 tons. But, you can easily install the J series hardware onto any C engine and wake it up a bit.

For fuel economy, I'd do the 1/2 ton 2WD version, and as you mentioned 3.08 would be as tall of a gear as I'd run.

@70 on flat ground you'd see between 21-25 MPG.

I've had two 3.42 geared 6.2 suburbans that would get betwen 19-21 MPG at 70 on the highway.

J

[argo]

I agree with john8662. I have a 93, and it is very nice, but not as nice as the 89-91 Burbs. To convert a C-code 6.2 to a J-code you want to swap the intake out for a J code intake. Alternatively, if you know how to weld aluminum or have a good friend who can, you can just remove your EGR valve, grind the mounting pads flat, and plug weld the EGR ports to block exhaust flow. I did that on my 1983 Olds 5.7L diesel to eliminate the EGR valve on that one. My Suburban started life as a TBI equipped 5.7L gas V8 with a 4L60E and 3.73 gears. I replaced the engine with a 6.2L J code engine from a 1984 Suburban C2500. It has the small C-code combustion chambers from a 1985 C-code engine that I scavenged parts from. I also used a 700R4. You want your overall gearing to be in the 2.6:1-2.8:1 range, including overdrive for maximum fuel economy at highway speeds. 3.73 gears with a 0.70 overdrive works out to a 2.611 final drive. A TH-400 or a TH-350 (and TH-350C) would be best paired with 2.73 gears. My 6.2 (which I optimized for maximum fuel economy) will deliver 27 MPG at 55-60 MPH. I can get 24 MPG if I keep it under 70. Also, around town I get about 22-23 MPG. I probably would get another 1-2 MPG overall if I had used a 3" or 3.5" single exhaust instead of a 2.25" dual exhaust with no crossover (originally designed for a 1984 Suburban). In fact, it is one of the two things I would do differently if I had the project to do again. The other item has to do with the TH700-R4. I don't like it, and I don't trust it. It runs fine, but it just feels flimsy to me. I should have used a TH-350C and 2.73 gears instead. I might have sacrificed 1 MPG doing it, but I would be much more confident in the overall durability of the truck. That is just my opinion, and there are many people who are happy with their 700-R4 transmissions. If I had done the big single exhaust and the TH-350C, my mileage might be identical, since the exhaust would make up for the slight loss of efficiency with the TH-350C and 2.73 gears. I wouldn't recommend that combination for something that you will tow with or haul a lot, but for my Suburban, which is just a family station wagon, it would work fine.

[Robyn]

X2

The 700R can be brought into the rhelm of "DECENT" with some serious $$$$ being tossed at them.

I have had 2500 Burb 4x4's with 4.10 gears and stock tires that would break the 20 mpg on the hwy with the "J" 6.2

Had a K5 Blazer with 31 inch tires, 3.42 gears and a "C" engine that got 24-25 Hwy, 20 city.

The great mileage numbers are certainly possible with lighter weight and tall gears.

As mentioned, the 89-91 rigs were very well apointed.

The 91 Burbs had a lot of stuff in the way of creature comforts and upgrades that were being readied for the introduction of the GMT400 class Burbs.

I have owned 2 1991 Burb 4x4's and loved them both.

I never seem to be able to hang onto them. :confused:

Good luck

Missy

[Edahall]

As previously mentioned, speed kills fuel economy on these rigs. They are not very aerodynamic. I get the best fuel economy on my 82 Suburban driving no faster than 60 mph. If you want to drive the speed limit in TX and not have it not affect fuel economy so much, lowering it would probably help it out a lot.

From what I've read, the older the 6.2's had more potential for higher fuel economy figures due to smaller precombustion chambers. However, they didn't have as much power. My 1982 Suburban was rated for 135 hp and it was definitely a slug and dangerously slow before the mods.

The earlier 700R4 transmissions were garbage. I believe it was 1987 when a bunch of improvements were incorporated into this transmission. I installed a 1989 model and so far, it has not fallen apart. However, I'm very careful with it and don't tow in O/D. If I had to do it over again, I would have converted it over to manual transmission. I would have gone with an NV4500 5 speed transmission or SM465 and 2.73 rear end. As mentioned, the 700R4 can be made strong but it costs a lot of money.

[DSM]

Thanks! That points me in a direction to look but, finding a 89-91 is like a needle in a haystack these days.

BTW, Edahall, What kind of mileage do you see from that Cummins powered burb? My old 92 D3500 1 ton dodge has shown me 24 mpg with a 4.10 diff.
If I had the time and space to work I'd be incline to build up a rig such as yours. Meanwhile I'll keep searching...

[Edahall]

Thanks! That points me in a direction to look but, finding a 89-91 is like a needle in a haystack these days.

BTW, Edahall, What kind of mileage do you see from that Cummins powered burb? My old 92 D3500 1 ton dodge has shown me 24 mpg with a 4.10 diff.
If I had the time and space to work I'd be incline to build up a rig such as yours. Meanwhile I'll keep searching...

On a long trip driving conservatively, I get 26 mpg. That said, my 1982 Suburban does slightly better but it's 2 wheel drive and a lot lighter. I do really like the Cummins powered Suburban and will never sell it. I now hardly ever drive the 6.2 Suburban.

Just keep your eyes open and you'll find one. The best examples are usually found in CA. There's a big incentive to keep one of these beasts alive in CA due to not having to be bothered with emissions every year.

As far as cracked blocks, the only way to know for sure is pull the pan off. However, I personally wouldn't worry too much about it. I've seen engines with cracked blocks keep on going. To keep the bottom end together, either replace the harmonic balancer every few years or install a Fluid Damper. Also, make sure all the glow plugs are working.

[DSM]

I found a '91 1/2 ton but it has 280K miles. Price is a little steep for the mileage.
How many miles will these things go???

[DmaxMaverick]

I found a '91 1/2 ton but it has 280K miles. Price is a little steep for the mileage.
How many miles will these things go???

It depends on storage, care and maintenance. My '85 is about 600K, but doesn't look a day over 400K. 280K isn't bad if it was well maintained.

[coxfmly]

Here is an add from the "Orange County Craigs list" (calif) . Enter "1991 suburban" to see the pictures...good luck.

1991 CHEVY SUBURBAN, DIESEL POWERED, AUTOMATIC, RED SILVERADO INTERIOR, COLD AIR CONDITIONING, CLEAN TITLE, GOOD TIRES, PS, PB, TOW PACKAGE, RUNS GREAT, GOOD CONDITIONS, (310) 962-0135

122,000 miles. 2,900.00

[DSM]

Here is an add from the "Orange County Craigs list" (calif) . Enter "1991 suburban" to see the pictures...good luck.

1991 CHEVY SUBURBAN, DIESEL POWERED, AUTOMATIC, RED SILVERADO INTERIOR, COLD AIR CONDITIONING, CLEAN TITLE, GOOD TIRES, PS, PB, TOW PACKAGE, RUNS GREAT, GOOD CONDITIONS, (310) 962-0135

122,000 miles. 2,900.00

I'd snag that one up if closer.

I'm picking up a '84 doner diesel PU today for cheap. I can use it around the farm in the meantime or it might be a candidate 6.2 for that old 26 foot cabin cruiser we have. Never take it out anymore due to fuel cost.

Either way it will get me up to speed on the 6.2 engine.