Serving Central Illinois Since 2019

Tremont Knows a Truck That Runs Right.

From routine diesel maintenance to full engine overhauls, Cornerstone Classic Semis keeps Class 8 rigs rolling on IL-9 and every mile beyond. Built on hard work, backed by expertise.

(309) 925-3222 Our Services

Years Serving

Class 8

Specialization

IL-9

Local Base

Close-up of a diesel engine in a semi truck

Location

22319 IL-9
Tremont, IL 61568

What We Do

Complete Heavy-Duty
Repair & Maintenance

From preventive service to complex diagnostics, we handle the full spectrum of Class 8 diesel needs — so you stay on the road.

Engine Diagnostics & Repair

Advanced diagnostic tools and experienced hands for engine performance issues, fault code analysis, and complete rebuilds on all major diesel platforms.

Preventive Maintenance

Scheduled inspections, fluid changes, filter replacements, and comprehensive PM schedules designed to extend component life and prevent costly breakdowns.

Brake & Air Systems

Full brake inspections, pad and rotor service, slack adjuster adjustment, and complete air brake system diagnostics and repair for safety compliance.

Transmission & Driveline

Manual and automatic transmission service, clutch replacements, driveline component inspection, and differential repair for sustained power delivery.

Electrical & Electronics

Complete electrical system troubleshooting, wiring repair, alternator and starter service, and modern ECU-related diagnostics for current-generation trucks.

DOT Inspection Prep

Thorough pre-trip and post-trip inspection support, DOT compliance preparation, and corrective repair to keep your truck passing and legal on the road.

Inside the Cornerstone Classic Semis workshop in Tremont

About Us

Rooted in Tremont.
Built for the Road.

Cornerstone Classic Semis was founded on a simple belief: a semi truck deserves the same dedication and craftsmanship as any machine built for the long haul. Located right on IL-9 in the heart of Tremont, we've spent years earning the trust of local owner-operators and regional fleets who need dependable repair done right the first time.

Our shop specializes in Class 8 diesel powertrains — from routine oil changes and brake service to full engine teardowns and transmission rebuilds. We know these trucks carry livelihoods, and every hour off the road matters. That's why we focus on getting it right fast, with clear communication and fair pricing from the start.

Class 8 Diesel Specialists

Transparent Pricing

Local & Fleet Friendly

Fast Turnaround

Why Cornerstone

Numbers That Speak
for Themselves

We measure success by the trucks that keep rolling and the drivers who keep coming back.

Years in Business

Building a reputation one repair at a time, right here in Tremont since 2019.

100%

Class 8 Focus

We don't spread thin. Heavy-duty diesel is all we do, and we do it well.

IL-9

Convenient Location

Easy access right off IL-9, positioned for quick turnaround on your schedule.

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Repeat Customers

Most of our business comes from drivers and fleets who trust us to get it right.

What Drivers Say

Trusted on the Road

Word of mouth keeps our shop busy — and we're proud of every referral.

Brought my truck in after a breakdown on I-74 and had it back on the road the same day. Honest pricing and they explained exactly what was wrong. That's rare to find.

Mike R.

Owner-Operator

We've been bringing our fleet here for over two years now. Consistent quality, no surprises on the bill, and they treat every rig like it's their own.

Dennis T.

Fleet Manager

The best diesel shop between Chicago and St. Louis, hands down. They know Class 8 engines inside and out. I won't go anywhere else.

Jerry W.

Regional Driver

Get in Touch

Your Truck Deserves
a Cornerstone Shop

Give us a call or swing by the shop on IL-9. We'll get you scheduled and back out safely.

Call (309) 925-3222 Email Us

22319 IL-9, Tremont, IL 61568