thumping

[Rigs]

Hello, I own a 95 bronco xlt and it thumps when i take off and when I come to a stop. It has thumped for a couple of months now and recently got worse. It''s only worse when the check engine light is on. I know it sounds wierd. But that check engine light comes on and bam, it feels like someone hit me in the rear, it's that hard. I checked the u-joints, no play in them. I checked the rear pumpkin for fluid (just something easy). That's about all I checked out. Can anyone help me with some ideas as to what this may be? Thanks.

 

[bidibronco]

Speed sensor in the rear may be "thumping" your transmission in and out of gears.

 

[Seabronc]

Ditto no bidi's comment. Pull the codes and see what it says.

Good luck,

>-

 

[Broncobill78]

Yup, gotta second that motion. The Ck Engine light only comes on when the computer throws a code. So bring it to Napa, or AutoZone or CarQuest or whoever's nearby because almost *every* autoparts store out there these days has a codereader & will ck them for you for free (if the first place you ck doesn't then call around, I *promise* someone local reads them for free) . Find out what the Code is and you'll have a *whole* lot more to work with.

 

[blkwlf]

which came first, the thumping or the CEL? i had the same problem in my 95. Turned out it was the speed sensor but in the process, because of the late shifting and the 5g "thumping", the transmission was indicating a clutch slippage code(don't remember #) but as soon as the speeds sensor was replaced, all problems went away and i am now 6 months CEL free.

 

[Rigs]

which came first, the thumping or the CEL? i had the same problem in my 95. Turned out it was the speed sensor but in the process, because of the late shifting and the 5g "thumping", the transmission was indicating a clutch slippage code(don't remember #) but as soon as the speeds sensor was replaced, all problems went away and i am now 6 months CEL free.

The thumping came first. I guess the check engine light is telling the problem is getting worse because the thumping gets harder when the check engine light is on. I know that sounds strange but it's happening. Did you replace the speed sensor yourself? I am pretty handy but have never done that. I looked to see where it is and found it but just was wondering if it was that difficult to do??? Thanks.

 

[blkwlf]

it just takes a few minutes and the part cost less than $50 from the dealer. make sure you thoroughly clean around the old one first before you take it out. Use a stiff brush like a wheel brush and a can of air, otherwise you might get some dirt dropping inside the pumpkin. It might take a little twisting but the old one should just lift straight up. i would also make sure you have a good clean tight ground at the battery as this is a ground based system. i would also get the code pulled from you local auto parts store. they can also reset the computer after they pull the codes

 

[Rigs]

it just takes a few minutes and the part cost less than $50 from the dealer. make sure you thoroughly clean around the old one first before you take it out. Use a stiff brush like a wheel brush and a can of air, otherwise you might get some dirt dropping inside the pumpkin. It might take a little twisting but the old one should just lift straight up. i would also make sure you have a good clean tight ground at the battery as this is a ground based system. i would also get the code pulled from you local auto parts store. they can also reset the computer after they pull the codes

Thanks. I noticed the wiring that comes from the speed sensor. Does the sensor disconnect from the wiring? I didn't take notice of that. Thank you very much for the tip.

 

[blkwlf]

yes, its just a plug

 

[walnuts75]

Maybe the thumping is your slip joint in the rear drive shaft. Mine had a loud thumping in the rear and at first I thought it was the tranny, but it turned out to be the slip joint. It got worse when it warmed up and sounded like I ran over a cow or hit a big speed bump. I fixed this problem by taking out the rear drive shaft and pulling the two pieces apart. Then I slammed some grease into the open end of the shaft and lubed up the shaft part that goes into the open end. My Bronco has been thump free ever since.

As far as your check engine light, I don't know, sorry.

 

[Rigs]

which came first, the thumping or the CEL? i had the same problem in my 95. Turned out it was the speed sensor but in the process, because of the late shifting and the 5g "thumping", the transmission was indicating a clutch slippage code(don't remember #) but as soon as the speeds sensor was replaced, all problems went away and i am now 6 months CEL free.

Hey, thanks for all the info., really. I had the codes read at autozone and I had to fault codes. 1 was the throttle positioning sensor (I changed that yesterday) and the other was the canister purge valve. What the heck is the canister purge valve? Does anyone have a picture of that? Anyway, I was getting a higher idle in my bronco and now I am not because I changed the throttle sensor. Cool beans. Still getting the thumping though. Does anyone think it's not the speed sensor anymore because there was no code showing up for anything like that. Should i just go out and get the speed sensor for the rear anyway?

 

[walnuts75]

Hey, thanks for all the info., really. I had the codes read at autozone and I had to fault codes. 1 was the throttle positioning sensor (I changed that yesterday) and the other was the canister purge valve. What the heck is the canister purge valve? Does anyone have a picture of that? Anyway, I was getting a higher idle in my bronco and now I am not because I changed the throttle sensor. Cool beans. Still getting the thumping though. Does anyone think it's not the speed sensor anymore because there was no code showing up for anything like that. Should i just go out and get the speed sensor for the rear anyway?

It wouldn't hurt to get a new speed sensor. They're cheap and take about four seconds to change. I really think the thumping could be your slip joint in the driveshaft. Does it thump when you first take off and thump again when coming to a stop? Does it get worse the longer you drive it? That's what mine did. Its not hard to fix at all.

 

[Rigs]

It wouldn't hurt to get a new speed sensor. They're cheap and take about four seconds to change. I really think the thumping could be your slip joint in the driveshaft. Does it thump when you first take off and thump again when coming to a stop? Does it get worse the longer you drive it? That's what mine did. Its not hard to fix at all.

You couldn't be more zero'd in on the problem! It does happen when it takes off and comes to a stop. Thanks.

 

[Rigs]

It wouldn't hurt to get a new speed sensor. They're cheap and take about four seconds to change. I really think the thumping could be your slip joint in the driveshaft. Does it thump when you first take off and thump again when coming to a stop? Does it get worse the longer you drive it? That's what mine did. Its not hard to fix at all.

Was it the spline of the shaft you greased? What grease did you use? Thanks.

 

[walnuts75]

Yes, it was. I used lithium-based grease that you can get from NAPA or any other auto parts store. Take the two pieces of the drive shaft apart and apply spoonfuls of grease on both the splined shaft and on the inside of the tube part of the other piece. When you put the two pieces back together it should overflow with grease and make farting noises, that's just the slip joint telling you that you did a good job.