clunking noise

[ford/moparguy]

Hello My question is this. My 78 ford bronco clunks when it is shifted to reverse. I have a 351m, c6 automatic, np205 transfercase 79 ford bronco yokes and driveshaft on the rear. I just upgraded from the stock 78 yokes in the rear because my driveshaft was worn out and the one I bought had the larger 1330 ujoints. I am wanting to know what could cause this as the rear drive shaft is solid and the slipyoke is solid and new ujoints and everything is greased. My bronco did this before because the old slipyoke was worn out and damaged the cardan joint aka cv joint on drive shaft as well as ujoints. I would really like to know what all could cause this and what to check now??

Thanx Lee

 

[Broncobill78]

Well, there are only so many things that will cause it to do that. You ck each part of the puzzle and eventually you'll find the problem. If it's clunking hard when you shift into reverse there are only so many parts involved. Starting with the driveshaft it can be either the U-joints or the slip-yoke. If the shaft & U's are cool then you have to move on. You've swapped yoke but I'll assume that everything went together well and nothing was forced together or possibly left loose, sometimes when a shop does the work the guys are not as interested in getting things right/tight as they are with their *personal* vehicles. Not that I'm saying that's the case here but I've certainly seen it happen before. If the shaft & yokes are OK then you have to look at each end of the shaft. Worn out differentials can wind up with more backlash then they're supposed to have. Also, some differentials have more backlash built into them than others. The first time I ran a Detroit Locker I had this *exact* problem. I was convinced the dealership tech had done a $hitty job until I read thru the manual and saw for myself just how much backlash was specified. It was a bit unnerving to have it clunking like that but everything was well within spec so it was just something I had to get used to. If the driveshaft & rearend are cool then you're left looking at the tranny & transfer case. If there's too much backlash in either one of *those* then there really aren't any quick-fixes and you're looking at exploratory surgery to find & fix the problem.

 

[ford/moparguy]

Well, there are only so many things that will cause it to do that. You ck each part of the puzzle and eventually you'll find the problem. If it's clunking hard when you shift into reverse there are only so many parts involved. Starting with the driveshaft it can be either the U-joints or the slip-yoke. If the shaft & U's are cool then you have to move on. You've swapped yoke but I'll assume that everything went together well and nothing was forced together or possibly left loose, sometimes when a shop does the work the guys are not as interested in getting things right/tight as they are with their *personal* vehicles. Not that I'm saying that's the case here but I've certainly seen it happen before. If the shaft & yokes are OK then you have to look at each end of the shaft. Worn out differentials can wind up with more backlash then they're supposed to have. Also, some differentials have more backlash built into them than others. The first time I ran a Detroit Locker I had this *exact* problem. I was convinced the dealership tech had done a $hitty job until I read thru the manual and saw for myself just how much backlash was specified. I was a bit unnerving to have it clunking like that but everything was well within spec so it was just something I had to get used to. If the driveshaft & rearend are cool then you're left looking at the tranny & transfer case. If there's too much backlash in either one of *those* then there really aren't any quick-fixes and you're looking at exploratory surgery to find & fix the problem.

Thanx for the reply Broncobill and I will check everything again and will post. Now that I think about it there was I think a little play in my Differential I will have to check it as soon as the rain stops.

Thanx again Broncobill

 

[wes p]

check the bearings in your engine. my 79 bronco makes the same noise when you rev it past a certain RPM, and i found out that its just the bearings in the engine