Tach going backwards with MSD 6AL
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Supreme Member
Joined: Jan 2000
Posts: 1,199
Likes: 93
From: Mississauga, Ontario Canada
Car: 1987 GTA
Engine: 5.7
Transmission: T5WC
Axle/Gears: 3:27
Tach going backwards with MSD 6AL
Of course this couldn't go easy. I expected nothing less. Got the 6AL hooked up using the MSD dual coil connector harness. Works great....until 3000RPM, then the tack goes backwards.
However the tach in the Tunerpro dashboard is reading just fine. Now what the hell do I do? What from Rabbit Hole performance do I need now?
However the tach in the Tunerpro dashboard is reading just fine. Now what the hell do I do? What from Rabbit Hole performance do I need now? Thread Starter
Supreme Member
Joined: Jan 2000
Posts: 1,199
Likes: 93
From: Mississauga, Ontario Canada
Car: 1987 GTA
Engine: 5.7
Transmission: T5WC
Axle/Gears: 3:27
Re: Tach going backwards with MSD 6AL
Never mind. Looks like an MSD 8910 is required. I think it's dropping off above 3000, not going backwards.
Joined: Sep 2000
Posts: 2,504
Likes: 195
From: Moorpark, CA
Car: '91 GTA, '92 T/A Convertible
Engine: GTA: 350 w/Vortec heads, T/A: 305
Transmission: Pro-built 700R4
Axle/Gears: GTA: 3.27, T/A: 2.73
Re: Tach going backwards with MSD 6AL
Had the same issue when I installed mine. Anything over 3k RPMs made the tach jump all over. The MSD tach adapter you found will fix the issue.
Thread Starter
Supreme Member
Joined: Jan 2000
Posts: 1,199
Likes: 93
From: Mississauga, Ontario Canada
Car: 1987 GTA
Engine: 5.7
Transmission: T5WC
Axle/Gears: 3:27
Joined: Feb 2017
Posts: 4,180
Likes: 574
From: Meriden, CT 06451
Car: 84 TA orig. 305 LG4 "H" E4ME
Engine: 334 SBC - stroked 305 M4ME Q-Jet
Transmission: upgraded 700R4 3200 stall
Axle/Gears: 10bolt 4.10 Posi w Lakewood TA Bars
Re: Tach going backwards with MSD 6AL
MSD Wiring Diagrams and Tech Notes
start at page 163
https://www.google.com/url?sa=t&rct=...2cjjf7ySEhwMzO
start at page 163
https://www.google.com/url?sa=t&rct=...2cjjf7ySEhwMzO
Joined: Sep 2000
Posts: 2,504
Likes: 195
From: Moorpark, CA
Car: '91 GTA, '92 T/A Convertible
Engine: GTA: 350 w/Vortec heads, T/A: 305
Transmission: Pro-built 700R4
Axle/Gears: GTA: 3.27, T/A: 2.73
Re: Tach going backwards with MSD 6AL
I'd have to go check, but IIRC, the wire comes with the spade connector T so you don't have to do any splicing. I'll go check when I'm on in the garage.
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Joined: Oct 2004
Posts: 4,528
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From: Henrietta NY
Car: 1984 Trans Am L69
Engine: Sniper EFI Powered 355
Transmission: WC T5 w/ Steel Support Plate
Axle/Gears: 3.42 10 Bolt Posi
Re: Tach going backwards with MSD 6AL
You could also try a series 10K 1/4w resistor. Both worked on my car
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Joined: Oct 2001
Posts: 12,223
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From: Il
Car: 1989-92 FORMULA350 305 92 Hawkclone
Engine: 4++,350 & 305 CIs
Transmission: 700R4 4800 vig 18th700R4 t56 ZF6 T5
Axle/Gears: 3.70 9"ford alum chunk,dana44,9bolt
Re: Tach going backwards with MSD 6AL
Had to do the same thing, of course being msd, the tach adapter quit a few yrs ago. Have also been through 4-5 6al boxes in 30 yrs.
Thread Starter
Supreme Member
Joined: Jan 2000
Posts: 1,199
Likes: 93
From: Mississauga, Ontario Canada
Car: 1987 GTA
Engine: 5.7
Transmission: T5WC
Axle/Gears: 3:27
Re: Tach going backwards with MSD 6AL
Got it wired in. Beyond simple with the dual coil harness. Literally plug and play, no cutting. Works like a charm.
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