tach/shifting problems
Thread Starter
|
Junior User
Joined: Jan 2003
Posts: 84
Likes: 0
tach/shifting problems
Hey Guys,
Bought a 91 F150, 302, auto w/od. Guy I bought it from was trying to replace water pump and broke stud off in block. So with his misfortune, he got frustrated and sold me the truck for $500. Lucky me. I got the broken stud out and replaced the water pump. Truck runs fine.
One problem, the tach reads 3500 rpms as soon as you crank it up. When you hit the pedal it crawls up to 4000 and when you let off, goes right back to 3500. He did say he had a used transmission put it in and I notice it shifts out very quickly (low rpms) and shifts pretty hard. Would a bad tach sensor be causing both of these problems? If so, where is the tach sensor located, how hard is it to replace and how much does it cost?
Thanks,
Jim
Bought a 91 F150, 302, auto w/od. Guy I bought it from was trying to replace water pump and broke stud off in block. So with his misfortune, he got frustrated and sold me the truck for $500. Lucky me. I got the broken stud out and replaced the water pump. Truck runs fine.
One problem, the tach reads 3500 rpms as soon as you crank it up. When you hit the pedal it crawls up to 4000 and when you let off, goes right back to 3500. He did say he had a used transmission put it in and I notice it shifts out very quickly (low rpms) and shifts pretty hard. Would a bad tach sensor be causing both of these problems? If so, where is the tach sensor located, how hard is it to replace and how much does it cost?
Thanks,
Jim
The Southernmost Mod
Joined: Dec 2004
Posts: 6,902
Likes: 20
From: Caracas, Venezuela
You'll probably need to replace the instrument cluster, but the first thing you should try is the VSS sensor, it will be located on top of the rear differential. Clean the terminals for both the E4OD tranny and the sensor and see if the problem goes away. if it doesn't, replace the sensor. Does the needle in the speedo jump erratically? if it does you could have a broken exitor ring (but by your symptoms i think this isn't the issue right now). Anyway, try the sensor before, if that doesn't work, check the connections to your cluster, else you'll have to replace the PSOM.
Don't run your truck for long without addressing this issue, it will hurt your expensive tranny.
Don't run your truck for long without addressing this issue, it will hurt your expensive tranny.
Fleet Owner
Joined: Oct 2005
Posts: 20,783
Likes: 1,751
From: Kentucky
The tachometer gets it's signal off the negative side of the coil. There is no direct correlation between the tach or transmission. The PCM does use the engine RPM and VSS, as well as a few other signals, to determine when and how "hard" to shift.
Before replacing any parts check for codes.
Before replacing any parts check for codes.
Thread
Thread Starter
Forum
Replies
Last Post
fhafer
Pre-Power Stroke Diesel (7.3L IDI & 6.9L)
3
Dec 26, 2010 04:02 PM
Groundpounder0331
1994.5 - 1997 7.3L Power Stroke Diesel
7
Jul 13, 2010 11:04 AM
79boston150
1987 - 1996 F150 & Larger F-Series Trucks
2
May 6, 2009 06:43 PM
IronHorseDriver
1983 - 2012 Ranger & B-Series
8
Apr 19, 2008 06:58 AM
