automatic with bad tach

[redneckaggie]

Ok its my sis's truck 93 idi e40d. the tach is going bad(just picks when it wants to read) will this affect the tranny because of the electronics? thanks

 

[1dieselman]

If it is just the tack going wacky it shouldn't affect the tranny but if it is the tack sensor on the timing cover or bad wiring yes it will

 

[Shadetreemechanic]

If it is just the tack going wacky it shouldn't affect the tranny but if it is the tack sensor on the timing cover or bad wiring yes it will

Well put.

 

[Smokey73]

When my '90 model's cam sensor when out. The rpm's would jump around sometimes and it would act like it wanted to shift out of od for no reason, but I don't think it ever would actually shift out, unless it needed to.

 

[1dieselman]

The tach sensor, fipl (on side of IP) and vss all provide input to tell the tranny when to shift and for converter lock/unlock. The brake light switch also inputs for converter unlock

 

[redneckaggie]

ok well the od light blinks when it idles because the tach goes completely dead so im prob going to replace it thanks guys

 

[1dieselman]

I would try the sensor first

 

[redneckaggie]

that is what i was refferring to i dont think the actual gauge is bad but can you connect an aftermarket tach to the stock sensor to check which it is or do aftermarket tachs have their own sensor

 

[1dieselman]

Most aftermarket tachs that I know of use their own sensor. The factory tach and sensor counts every tooth on the gear and the aftermarket tachs I've used in the past a magnet was epoxied to the harmonic balancer and gets counted just once every revolution.

 

[Shadetreemechanic]

ok well the od light blinks when it idles because the tach goes completely dead so im prob going to replace it thanks guys

You can try cleaning the sensor first. If it has oil or grime on it it will act just as you are describing.

 

[redneckaggie]

think that dad cleaned it but i will try that thanks.

 

[6.9poweredscout]

these motors have a crank position sensor? how come i never saw one on my 6.9? mine sometimes feels like it jumps outta gear for a split second, like the rpms will bounce, and in OD it's like it wants to shift out and the rpms are funny.

-Jon

 

[1dieselman]

NO, there's no CPS we are talking about the tach sensor in the top of your IP gear housing.

 

[Cat_Rebel]

Just bite the bullet & buy a new tach sensor from the dealer. I had to on mine a week or 2 ago & it finally works & shifts right.

 

[redneckaggie]

appreciate it do you know about how much it was and maybe a part number