Dial In Your Driveline Angle Without Cutting a Single Weld
Swapping a transmission in a 1978 to 1988 GM G-Body means fighting the factory crossmember every time the driveline geometry changes. The UMI3108-R Modular Adjustable Transmission Crossmember replaces that fixed mount with a 5 position CNC billet aluminum system that bolts into the stock subframe holes, so you can correct pinion angle and transmission height on the bench instead of under the car.
Key Features
- Laser cut tab and slot design for a lightweight, high strength mounting plate
- 5 position CNC machined billet aluminum transmission mount for precise height adjustment
- CNC machined billet aluminum spacer included for 1978 to 1981 frames
- Large cutouts for oversized dual exhaust systems, no exhaust clearance modifications needed
- Confirmed compatible with TKO, TKX, 200R4, 700R4, TH350, TH400, T56, 4L60, 4L65, 4L80 and 6L80 transmissions
- 100 percent bolt in installation using factory subframe mounting holes
- Durable Tiger Dry Lac powder coat finish in red
- Designed and manufactured in the USA from North American raw materials
Fitment Table
| Year Range | Make | Model |
|---|---|---|
| 1978-1987 | Buick | Regal |
| 1978-1987 | Chevrolet | El Camino |
| 1978-1983 | Chevrolet | Malibu |
| 1978-1988 | Chevrolet | Monte Carlo |
| 1978-1987 | GMC | Caballero |
| 1981-1988 | Oldsmobile | Cutlass |
| 1982-1986 | Pontiac | Bonneville |
| 1978-1987 | Pontiac | Grand Prix |
Specifications
| Detail | Value |
|---|---|
| MPN | UMI3108-R |
| UPC | Not assigned by manufacturer |
| Brand | UMI Performance |
| Color | Red powder coat |
| Total Brace Weight | 22 lbs |
| Material | CNC machined billet aluminum, laser cut steel |
| Adjustment Positions | 5 position transmission mount |
| Transmission Compatibility | TKO, TKX, 200R4, 700R4, TH350, TH400, T56, 4L60, 4L65, 4L80, 6L80 |
| Not Compatible With | TR6060 |
| Country of Origin | United States |
What’s Included
- UMI3108-R modular transmission crossmember assembly
- CNC machined billet aluminum transmission mount
- CNC machined billet aluminum spacer for 1978 to 1981 frames
- High grade mounting hardware
About UMI Performance
UMI Performance designs and manufactures chassis, suspension and driveline components for GM muscle cars entirely in the United States. Every part is engineered by racers who use their own track and street experience to solve real fitment and handling problems, then built from North American raw materials with precision welds and laser cut components for a durable, repeatable fit.
Related Parts on Our Site
- UMI Performance 68-72 GM A-Body Tubular Upper & Lower Control Arms
- UMI Performance 82-92 GM F-Body Boxed Style Weld-In Subframe Connectors
FAQ
What is the UMI3108-R?
The UMI3108-R is a modular, 5 position adjustable transmission crossmember for 1978 to 1988 GM G-Body vehicles, finished in red powder coat. It bolts into the factory subframe holes and lets you fine tune transmission height and driveline angle for a wide range of automatic and manual transmissions.
Does the UMI3108-R require any drilling or cutting?
No. It bolts directly into the existing factory subframe mounting holes on all 1978 to 1988 G-Body frames, so no drilling, cutting or welding is required for installation.
Will this crossmember clear a large diameter dual exhaust?
Yes. The brace design includes large cutouts specifically sized to provide clearance for oversized dual exhaust systems.
What transmissions work with the UMI3108-R?
It is confirmed to work with TKO, TKX, 200R4, 700R4, TH350, TH400, T56, 4L60, 4L65, 4L80 and 6L80 transmissions. It is not compatible with the TR6060.
Do I need the aluminum spacer for my car?
The CNC machined billet aluminum spacer is only required on 1978 to 1981 G-Body frames and is included in the box for those applications.
Which transmission mount should I order?
Most applications use the shorter 3.1158 mount. A taller 3.1108 mount is available if needed. If you are unsure, install the shorter mount first and measure before ordering the taller option.
Is the UMI3108-R adjustable after installation?
Yes. The laser cut tab and slot design combined with the 5 position billet aluminum mount allows you to adjust driveline angle and transmission height even after the crossmember is bolted in.
What vehicles use this crossmember?
This crossmember fits the 1978 to 1988 Buick Regal, Chevrolet El Camino, Chevrolet Malibu, Chevrolet Monte Carlo, GMC Caballero, Oldsmobile Cutlass, Pontiac Bonneville and Pontiac Grand Prix, based on the exact year ranges shown in the fitment table above.
Install Instructions
- Support the transmission with a suitable transmission jack before removing the factory crossmember.
- Remove the factory transmission crossmember from the subframe mounting holes.
- Position the UMI3108-R modular crossmember into the existing factory subframe holes and loosely install the mounting hardware.
- Install the CNC machined billet aluminum spacer if your vehicle is a 1978 to 1981 model.
- Attach the billet aluminum transmission mount at the appropriate one of the 5 adjustment positions for your transmission and desired driveline angle.
- Raise the transmission into place on the new mount and torque all mounting hardware to manufacturer specification.
- Verify exhaust clearance and driveline angle, then make final adjustments as needed before lowering the vehicle.
