Another try....at fixing my tach - PeachParts Mercedes-Benz Forum

tyl604 · #1 12-22-2011, 12:39 PM

pawoSD - my 81 SD tach has not worked since about 86; when it does it exhibits the same strange pegged or zero reading or uncontrolled bouncing. Then a few months ago I got a rebuilt tranny installed. The tranny would not shift but the tach now worked perfectly. I drove it about five miles back to the tranny shop with the tach working fine. They installed another rebuilt tranny and tach has not worked since. Except for a sporatic 100% peg or a few bounces. So what happened between the first replacement tranny and the second; why did it work with the first replacement and not the second? Almost sounds to me like whatever attaches to the tranny could need tightening up, loosening, or something.

Ideas?

pawoSD · #2 12-23-2011, 12:54 AM

Quote:

Originally Posted by tyl604

pawoSD - my 81 SD tach has not worked since about 86; when it does it exhibits the same strange pegged or zero reading or uncontrolled bouncing. Then a few months ago I got a rebuilt tranny installed. The tranny would not shift but the tach now worked perfectly. I drove it about five miles back to the tranny shop with the tach working fine. They installed another rebuilt tranny and tach has not worked since. Except for a sporatic 100% peg or a few bounces. So what happened between the first replacement tranny and the second; why did it work with the first replacement and not the second? Almost sounds to me like whatever attaches to the tranny could need tightening up, loosening, or something.

Ideas?

The pickup for the tach is on the front of the engine on an 81SD, and the tach amp is on the driver side fender. Transmission swap shouldn't affect it at all unless they jarred something loose or did not connect something. Depends how they did the swap....engine pulled? Or from below?

tyl604 · #3 12-23-2011, 04:19 PM

They pulled it from below. I am leaning to something needing tightening down near/on the tranny but do not know what.