Will my early-90s Tahoe/Suburban TH350/TH400 or 4L60E bolt up to an LS without grenading, and what adapters are needed?
All three can bolt to an LS — they share the GM bellhousing pattern, give or take a couple of bolts — but each needs the right flexplate/converter setup:
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Most LS engines have a crank flange that sits about 0.400 in shorter than older GM engines relative to the bellhousing, even though the bellhousing bolt pattern is nearly the same. Older transmissions and their converters were built for the old position.
TH350: a dished flexplate (or dual-pattern flexplate) with the 10.75 in converter pattern, plus a converter adapter sleeve.
TH400: its converter uses the 11.5 in pattern, the same as an LS that came with a 4L80E. If your LS came with a 4L80E, space the factory flexplate out with an adapter. Otherwise use a flexplate with the 11.5 in pattern plus the spacing solution for your crank.
4L60E: LS 4L60E flexplates use the 11.062 in pattern. An early-90s truck 4L60E isn't an LS-spec unit: our transmission data notes LS versions use a 300 mm input shaft and an LS converter (non-LS units are 298 mm), so plan on the LS-correct converter.
Converter bolt patterns:
| Transmission | Converter bolt pattern |
|---|---|
| 4L60E, 4L65E, 4L70E | 11.062 in (sometimes listed as 11 or 11.08 in) |
| 4L80E, TH400 | 11.5 in |
| Powerglide, TH350, 700R4 | 10.75 in |
Also note that 2009+ LS engines use 8-bolt (or 9-bolt on the LS9) crank flanges, which need their own flexplates. Electronic transmissions (4L60E) also need a controller — see transmissions.
Yes, all of the older Chevy automatics bolt up to an LS: TH350, TH400, Powerglide, 700R4 and 4L80. You can buy an adapter flexplate, or use a stock LS 4L60E flexplate and enlarge the converter bolt holes. Either way you need the ~$22 hub adapter that sits between the converter snout and the center of the flexplate. We've found old small-block V8 vehicles to be the cheapest donors, and the LS drops into them with minimal effort.
Check this first:
- Confirm you have the converter hub adapter
- Match the flexplate converter bolt pattern to your converter
Based on what we've seen work across our own builds, our friends' builds and the wider LS community, reviewed by our lead shop tuner (over 20 years of LS and LT tuning experience). Every combination is different, so use at your own risk and check our safe tuning limits before any wide-open pass.
Go deeper
Check this first
- Identify the trans and its control needs (TV cable, standalone, or PCM).
- Check converter nose vs LS crank bore.
- Assess trans health before the swap - don't install a tired unit.
Try this, then this
- 1) Bolt pattern: direct fit, no adapter plate needed.
- 2) Crank adapter for converter nose + correct flexplate spacing.
- 3) Control: TV cable set with gauge (TH350/700R4) or trans controller/PCM (4L60E); big cooler.
How you know it's fixed
- Proper converter engagement, correct control setup, clean shifts, sane temps.
Still not fixed?
- Pump noise or no-move means converter spacing - pull it and re-measure before it eats the pump.
Every option we know of
| Maker / product | Part # | Fits | Price | Where | Status / notes |
|---|---|---|---|---|---|
| eBay/aftermarket Crank/converter nose adapter | varies | LS crank to older converter nose | about $22 | eBay (~$22 reported) | Available Verify engagement depth |
| Hughes Performance LS flexplate + adapter | HP4004 / HP3795 | Older autos behind LS | verify current | Hughes dealers | Current production Proven combo |
| TCI / US Shift Standalone trans controllers | varies | 4L60E electronic control | $600-800 | Summit | Current production Needed if not running a GM PCM |
Prices are approximate as of September 2026. We list every option we know of, including small shops and used parts we can't link to. Confirm fitment with the seller.