Is this normal?

WLF · #1 02-27-2005, 11:09 PM

I was checking the indexing on the drive shaft after a rebuild. When I pulled off the drive shaft I noticed that the tail shift on the transmission (the part that is splined to recieve the drive shaft) had some play. I could move it up and down 1/8 inch with my thumb.
Is it normal for this tail shaft to have some play after a complete rebuild? I thought it would be supported by bearings.
I never tried to move the one in the old trans so I just don't know.
Thanks in advance.

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dirtyd0g · #2 02-28-2005, 12:15 AM

No. It sounds like they did not replace the output shaft bushing. Those bushings are known to fail on 4r70w transmissions. There are modifications you can make to prevent it. Most builders are too lazy and/or do not have the right equipment to replace those bushings. They are not simple press in bushings like most transmissions.
Alan

LE PEW · #3 02-28-2005, 12:24 PM

Mine has a little play in it too. I've checked new trucks (97- 02s)on the lot and they had about the same amount of play as well.

Alan, you once mentioned a mod for pressure lubing a tailshaft bushing. Could you give some more detail about what all is involved?

dirtyd0g · #4 02-28-2005, 01:21 PM

The mod only works on 2wd models. Basically what you do is buy 2 fittings that are 18npt male threads with a 90degree dend and 3/16 inverted flare on the other end. Remove the extension housing and then take the rear bushing out of it. The best way is to cut that bushing out. Drill a 1/8npt hole in the side of the extension housing where the bushing goes so that you can install the fitting. Then deburr the housing to make sure the bushing will go in straight. Install the new bushing and then drill a .050 hole in the bushing centered in the previous hole. Install one fitting in that and the other in the line pressure port near the front of the trans. Then run a 3/16 brake line between them. Bam force lube modification.
Next time I do one I will get some pics. I believe factory tech will be offering a kit very soon.
Alan

WLF · #5 02-28-2005, 01:35 PM

I contacted the rebuilder. He states he did replace the tail shaft bushing and that a little play is normal as long as it is not leaking, which it is not. He has a very good reputation in this area. He says he will stand behind the rebuild. I guess there is nothing else I can do.

madferraristi · #6 03-01-2005, 09:41 AM

There will be two symptoms that will develope if your rear bushing has too much clearance, one would be a fluid leak and the other is a high speed driveshaft vibration.

WLF · #7 03-01-2005, 05:20 PM

Thanks Mad and everyone who responded.
I do have a very slight vibration. When I blew the cap on the u-joint it really beat up the drive shaft. They were supposed to send the drive shaft out to make sure it is true and to have it balanced. They forgot to do that so I am dropping it off on Thursday. They are going to send the drive shaft out for balancing and they are going to assess the tail shaft for excessive play.
Let’s hope that takes care of it.