1999 Used GMC Engines For Sale | Auto Power Source

89
verified 1999 GMC engines
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Up to 3 yrs
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1999 Used GMC Engines For Sale

1999 is the year GMC ran two trucks at once. The all-new GMT800 Sierra 1500 arrived on the Gen III small-block — 4.8L LR4, 5.3L LM7, 6.0L LQ4 — while the C/K Classic line carried on unchanged with the 5.0L and 5.7L Vortec, the 7.4L Vortec 7400 big-block and the 6.5L turbo-diesel. Nine engine families, 89 units, every one VIN-matched to your truck before it ships.

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Warranty On Every Unit
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Photos Before Shipment
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ASE-Tested & Verified
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Free Nationwide Shipping
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30-Day Money-Back
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Secure SSL Checkout

1999 GMC Engine Families

Which engine sits under which 1999 GMC, and how many of each we hold today.

Engine family Fits (1999) In stock
5.7L Vortec 5700 V8 (L31) C/K 1500-3500 Classic, Suburban, Yukon, Savana; gasoline and dedicated CNG 31
4.3L Vortec 4300 V6 (L35 / LF6) S-10, Sonoma, Jimmy, Safari, Envoy, Blazer, Savana, Sierra 1500; VIN W L35 and VIN X LF6 21
6.5L L65 Turbo-Diesel V8 C/K 2500-3500 Classic, 3500HD, Suburban, Savana 3500; VIN F 15
7.4L Vortec 7400 V8 (L29) C/K 2500-3500 Classic, 3500HD, Suburban 2500, Savana 3500; VIN J 10
5.0L Vortec 5000 V8 (L30) C/K 1500 Classic, 1500 Pickup, Savana 1500-2500; VIN M 5
4.8L Vortec 4800 V8 (LR4) GMT800 Sierra 1500 only; VIN V, automatic and manual builds 2
5.3L Vortec 5300 V8 (LM7) GMT800 Sierra 1500 and Sierra 2500; VIN T 2
2.2L Four (VIN 4) S-10, S-15 and Sonoma compact pickup only 2
6.0L Vortec 6000 V8 (LQ4) GMT800 Sierra 2500 only; VIN U 1
Total 89

Other GMC Model Years

Every model year we hold GMC engines for. Years without a link are in stock but have no year page yet — text us your VIN.

20242023202220212020201920182017201620152014201320122011201020092008200720062005200420032002200120001999
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Why Buy a 1999 GMC Engine from Auto Power Source

A 1999 GMC is the one model year where the badge on the tailgate tells you almost nothing about what is under the hood. The new GMT800 Sierra 1500 and the outgoing C/K Classic were built and sold side by side, and the engines do not cross over: a 5.3L LM7 out of a 1999-Up Sierra will not drop into a Classic, and a 5.7L L31 out of a C1500 will not go into the new body. We hold both lines, and we settle which one you have off your VIN rather than off the model name.

The spread in this year is wide — nine families across 89 units, from a 2.2L four in a Sonoma to a 7.4L Vortec 7400 in a 3500HD. The two that catch people out are the 5.7L and the 6.5L. The 5.7L L31 was sold as gasoline and as a dedicated CNG unit in the same trucks and vans, and the two are not interchangeable: different fuel system, different calibration, different emissions hardware. The 6.5L turbo-diesel is heavy-duty only and shares nothing with the small-block V8s. We list them as separate stock, not as one 5.7L bin.

Every unit goes through the same six steps before it is cleared: VIN-matching, ASE compression testing with a leak-down evaluation, noise and smoke verification on a run stand, full visual inspection of manifolds, accessories and — on the diesels — the injection pump, multi-angle photography sent to you for approval, and palletized freight. On twenty-six-year-old Vortec and 6.5L stock that run-stand step is where most of the rejections happen, which is the point of doing it before you pay rather than after.

You pay a fraction of reman pricing for factory GM engineering, ship free on a heavy-duty pallet anywhere in the continental U.S., and get up to a 3-year warranty with 30-day money-back. If you are not sure whether your truck is a 1999-Up new body or a Classic chassis, text the VIN to +1-307-441-5554 and we will tell you which line you are on before you spend anything.

📱 Fastest way to match: text us your VIN, get options in minutes.Text Your VIN →

Your 1999 GMC Engine Options: Compared

Most 1999 GMC owners face four real choices when the engine fails:

← Swipe sideways to see all columns →
Option Cost Reliability Warranty Fitment Match
Used OEM (this collection) $$$ Best Value High — tested Included VIN-matched
New OEM (dealer) $$$$$ 2-4× more High Manufacturer Exact
Aftermarket / Reman $$$$ Varies 6-12 mo May adapt
Junkyard $ Cheapest Unknown None DIY

Tested used OEM hits the sweet spot — same engineering as new, fraction of the cost.

1999 GMC Engine Buying Guide

5 things to verify before buying a used 1999 GMC engine:

  1. Read the 8th VIN digit, not the badge. On a 1999 GMC the 8th digit is the engine code: W and X are the 4.3L V6, M the 5.0L, R the 5.7L, J the 7.4L, F the 6.5L turbo-diesel, V the 4.8L LR4, T the 5.3L LM7, U the 6.0L LQ4, and 4 the 2.2L four. Two trucks can both say 5.7L and still need different engines.
  2. Settle new body versus Classic first. The GMT800 Sierra 1500 and Sierra 2500 are the "1999 Up" listings; the C/K 1500-3500, 3500HD and the "2000 Down" / "2001 Down" trucks are the outgoing GMT400 Classic. Block, accessory drive and mounts differ across that split, so nothing carries over between the two lines.
  3. Check gasoline against CNG on the 5.7L. Ten of the thirty-one 5.7L units in stock are dedicated CNG — C/K 2500 and 3500, 3500HD, the Classic 1500 pickups and Savana 3500 all shipped both ways. The CNG unit has its own fuel system and calibration and will not run on gasoline. The VIN digit is the same for both, so the fuel type has to be confirmed separately.
  4. Treat the 6.5L diesel and 7.4L big-block as their own families. Both are heavy-duty only and share no parts with the small-block V8s. The 6.5L turbo-diesel appears across the C/K 2500-3500, 3500HD, Suburban and Savana 3500; the 7.4L Vortec 7400 across the 2500-3500 trucks, Suburban 2500 and Savana 3500. Confirm chassis class before ordering either.
  5. Confirm the match with your own VIN before you order. Your VIN settles the engine code, drivetrain and build split in one step. Text it to +1-307-441-5554 and we will confirm in writing exactly which unit fits your vehicle before you pay.

Our ASE-certified technicians verify every one of these points against your VIN before any unit ships.

📞 Need help choosing the right 1999 GMC engine? Talk to our team live.Call 1-877-313-8995

Frequently Asked Questions

How many 1999 GMC engines do you have in stock?
89 tested units as listed, across nine engine families. The count on this page is live active inventory, not a catalogue figure.
What is the difference between a 1999 Sierra 1500 and a 1999 C1500 engine?
The Sierra 1500 (1999 Up) is the new GMT800 truck on the Gen III small-block — 4.8L LR4, 5.3L LM7. The C1500 is the outgoing GMT400 Classic on the 5.0L L30 or 5.7L L31. They are different engine families and do not interchange, even though both were sold as new 1999 GMC trucks.
Is the 5.7L CNG engine the same as the 5.7L gasoline engine?
No. The dedicated CNG 5.7L has its own fuel system, calibration and emissions hardware. It carries the same VIN R code as the gasoline unit, so the fuel type has to be confirmed separately from the VIN. We hold both and list them as separate stock.
Do you have the 6.5L turbo-diesel for a 1999 3500HD?
Yes — the 6.5L L65 turbo-diesel is one of the larger families in this year, across the C/K 2500 and 3500, the 3500HD, Suburban and Savana 3500. Confirm your chassis class with us before ordering, because the HD fitments differ.
Is there an 8.1L or a Duramax in 1999?
No. Neither existed yet. In 1999 the top gasoline engine is the 7.4L Vortec 7400 big-block and the only diesel is the 6.5L turbo-diesel. The 8.1L arrives for 2001 and the Duramax for 2001 as well.
What is the warranty, and what does testing cover?
Up to 3 years depending on the unit, with the exact term on each product page. ASE-certified technicians compression-test every cylinder, run a leak-down evaluation and verify noise and smoke on a run stand before anything is cleared for sale.
How long until it arrives?
Prep and ship is 3-5 business days; freight transit is 2-3 business days after dispatch. Shipping is free on a heavy-duty pallet anywhere in the continental U.S.
What if I do not approve the photos?
Every dollar back — no restocking fee and no return freight charge. Multi-angle photographs of the actual unit go to you before we ship and before you are committed.
🏆 Earn $500 with Our Rewards Program
Every GMC engine you buy earns rewards. 10 orders (yours or referred) = $500 cash credit. Silver, Gold, and Platinum tiers with discounts, priority support, and private inventory access.
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100K+
Engines+Transmissions In Stock
0%
fitment-related returns
All 50
states covered, free freight
36
brands covered

Our 6-Step Inspection & Shipping Process

Every 1999 GMC engine we ship has been through these six steps:

1. VIN-Matching
We match the donor VIN to your VIN to confirm engine code, generation, emissions calibration, and drivetrain fit.
2. Tested & Verified
ASE-certified technicians compression-test every cylinder and run leak-down evaluation on engines. Transmissions are Shift-Tested through all gears.
3. Noise & Smoke Verification
Units are run to verify normal mechanical sound and clean operation — catches internal wear static tests miss.
4. Visual Inspection
Every accessible component is inspected: turbos, manifolds, valve covers, AFM/DFM lifters, accessories, sensor harnesses.
5. Photograph & Catalog
Multi-angle photos sent to you BEFORE we ship for your approval.
6. Palletize & Ship
Strapped on a heavy-duty wooden pallet, shipped via freight at no charge.

Our Photos-Before-Shipment Guarantee

Before any engine leaves our warehouse, we send you multi-angle photographs. You approve. If you do not approve, you get every dollar back — no questions, no restocking fees, no return freight charges. On top of 30-day money-back and the warranty included with every unit. Browse all 89 1999 GMC engines below.

✉ Email Us at info@autopowersource.com
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