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Slack in rear driveshaft

5K views 31 replies 9 participants last post by  jopes 
#1 ·
Mine is a 1995 5.0L, E4OD, 4x4 stock Bronco. There is a lot of slack in the rear driveshaft. The truck shifts very hard when it is running above 45 mph. When transmission mechanics look at the truck, they say it could be the transmission, the transfer case and the rear end. Of course, they have offered to rebuild all three. Is there a way to determine which it might be.

Thanks.
 
#6 ·
Slip joint in shaft
Loose pinion nut

Can you get under it and see where there is play?

Don't ever go back to that shop if their answer starts with "It could be... we'll rebuild all 3". Unless you wanna pay them to throw parts at it.
 
#7 ·
Havent checked the slip yokes, how do you do that? No the transmission doesnt slip at all. It actually shifts pretty good. What I hate about it is that at about 42 mph, if I try to accelerate rapidly, rather than have the transmission down shift immediately, it first feels like it hesitates, then downshifts very hard. When it then shifts to OD or 4th gear, it is a very hard shift, so much so passengers say it sounds like the transmission is about to fall out.

The driveshaft slack is such that if you reach up and grab the drive shaft, it turns significantly. I can't say how much now, but I can go under the truck and report back. Its just that when I took it to shop, the shop wanted to rebuild transmission, transfer case, and rear differential which seemed excessive to me.

THe truck now has 148K miles on it.

James
 
#12 ·
if it was the it's actually a slip joint it would be more of a fwd/aft movement unless the splines were fubar. its the joint between the 2 parts of the driveshaft under the rubber boot. you need to drop the driveshaft to inspect it. if you do a search on here there is a step by step thread on how to lube it.
 
#13 ·
When was the last time the transmission fluid was changed? It could be something as simple as gunk clogging up the lines in the transmission.

If you plan on changing the fluid, make sure you drop the pan so you can check for any debris or mud in there as well.
 
#16 ·
its been about a year. the fluid was old looking but only fine fuzz on the pan magnet, no metal pieces at all. I then changed the valve body to one of those "Punisher Valve Bodies" as well as the soloniod pack in the transmission. Again, no metal parts in the fluid.
 
#15 ·
Maybe not, but finding metal shavings in the pan would go a long way towards figuring out what is going on.
 
#20 ·
if it was the slip joint the front 1/2 and the back 1/2 of your driveshaft wouldn't move as one. if you can have someone turn the driveshaft while you look at the ring and pinion gear if you still have the diff cover off it should help you see where the slack is coming from. I would bet its something in the rearend. cant be the trans or transfer case unless it is two separate problems. even if your trans and t.c are in neutral the driveshaft wont move unless its on jacks. does this make sense ?
 
#21 ·
the diff cover is not off now but I can certainly take it off again and do as you say. When I had the truck at the trans shop a couple weeks ago, it was on a lift. I don't know if the trans was in gear, neutral or park but the obvious drive shaft slack was noted.

If I remove the cover and jack up the truck, will the ring gear and pinion not have any delay in turning when the drive shaft is spun if all is well?
 
#22 ·
A thought just occoured to me. Has any work been done to the diff? Such as a ring and pinion swap? If the pinion wasn't tightened down properly, it can cause the knocking you're describing. Depending on how long its been knocking, you could have either damaged teeth in the gears, or damaged pinion bearings. If you're lucky, you won't have any damage and simply tightening the pinion nut will do the trick.

If you do tighten the nut, when you remove the driveshaft flange, rebolt it on so that only half the flange is on the mounting plate. I know from personal experience that simply apply the parking brake may not hold the axles tight enough to apply proper torque (probably why the nut didn't get tight enough.) By rebolting the flange offset like this, the transmission will prevent the pinion from spinning and allow for proper torqueing of the nut.
 
#27 ·
A. Disconnect the rear drive shaft from the differential yoke and pull the slip joint apart and check the shaft groves for damage, clean and relube using Mobil 1 synthetic grease which will take up the slack and eliminate the clunk and hard shifting, it worked wonders for me when I rebuilt both my shafts relubing the slip joints made a huge difference. Make sure you don't clean off the "blue teflon coating" on the shaft groves it's OEM and there for a reason.

B. If that doesn't solve the issue then have the ring and pinion checked, adjusted/spec torqued correctly...there should be a small amount of play or "backlash" so the gear oil can circulate around the gears to keep them from swelling from over heating moving parts.

Good Luck ~ :thumbup
 
#28 ·
I have a question, and sorry if this is hijacking your thread.

I think my bronco has a similar issue that yours is having, with the rear driveshaft clunking, but mine is coming from the transfer case flange yoke, and appears to have excessive up and down movement, which is causing the clunk. I disassembled the driveshaft and found a broken spring in the centering ball on the flange yoke, replaced the whole yoke, and reassembled. It solved the clunk for all of 10 miles and it is doing it again.

any ideas of what would be causing this issue?
 
#31 ·
You can't, just, re-tighten a pinion yoke/flange nut. There is a metal crush sleeve behind it that sets pinion pre-load. Crush sleeves are made to be used once. If you screw up the pre-load adjustment during assembly, you have to throw away the crush sleeve and start over. So, simply re-tightening the yoke/flange nut compresses the crush sleeve past its initial pre-load torque.

No offence to anyone, but, DO NOT DO THIS. If your pinion flange is loose, it means the original thread locker that came on the pinion nut has failed and the nut has worked itself loose with use. Re-tightening it after initial pre-load has been established during factory set-up will cause damage to the pinion bearings over time.

If you're pinion flange is loose, then you may have, already, sustained pinion bearing damage. In which case, you need to inspect and re-build the pinion housing. Also, fully inspect the other components (ring gear, side bearings, spider gears, etc.) for unusual wear. All these things work together in the housing, so, one failure can cause a chain-reaction.

Eric
 
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