Dreaded Thump!
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Freshman User
Joined: Mar 2004
Posts: 25
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Dreaded Thump!
Ok folks, I've read all through the threads on the common "thump" sound many are hearing when you take off from a standing start. Here's my two cents worth....I bought a 96' F150 Supercab 4x4 351 and the E40D a few weeks ago. This truck has the limited slip rear end also. I purchased it from a 73 year old man who had put just over 50k miles on it since new and I doubt it had ever been in 4 wheel drive. I am 100 percent convinced he never abused it based on the truck's condition. The differential and pinion have no excessive play on this truck, there is no slop in the U-joints and the slip yoke inserts in the transfer case and the splines are constantly lubed by transfer case fluid. There is no sign of play or binding in the yoke. I was pretty stumped at that point. On a whim, today I switched off the overdrive to see what would happen and presto...the "thump" went away when leaving from a standing start. When I re-engage the overdrive the "thump" comes right back. I'm leaning heavily toward that "thump" we here being the torque converter prematurely locking up when you take off. Thoughts?
Senior User
Joined: Nov 2003
Posts: 115
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From: Salem, MA
I just diagnosed a noise under my truck that was a click as i left the line not so much a thump turned out to be a crack in the tranny crosmember! not sure if it is at all related to your problem. Also a friend of mine had a noise as he was talking off the line in his case the problem turned out to be loose/ worn side/spyder gears. But seeing as how your problem is closly related to the OD then i think you may be on the right track. Both mine and my friends trucks are M5OD manuals
New User
Joined: May 2004
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Thump research
I have a 96 Bronco, E4OD,1356 with a thump on start up, and occasionally just before coming to stop. In searching the web, I came across an article on the Torque Converter Lockup Solenoid. It's located under the pan. I have gone any further, but it's something I'll keep in mind. The other thing I've tried is to lock out the hubs, place T/C in 4H. The thump was non-existant upon take-off. I'm not convinced on the 'solenoid' theory, so I'm still researching.
