-73 Eldorado gear change rough after drive shaft change ????

[Finndorado]

It`s me again..

Yesterday I got my Eldo back from repairman, he changed both CV axles and the bearings.
When I left hi`s place I noticed a slight play somewhere when I push gas pedal down/up/down.
When I got home I noticed that when shifting gear forward-reverse-forward (in place with break on)
there is a powerful "klonk" felt and heard, especially shifting To reverse.
Is it possible that this could have something to do with the repair, or is it completely something else ?
I looked at the CV`s from under hood when friend was shifting, the play seems not to be in CV..I think ?

Thanks again !
Mika

[Cadman-iac]

If it didn't do that before you had it repaired,  then it's definitely something in the driveline.  Either he didn't tighten something,  or it didn't fit correctly and has too much play in it.
I don't believe there's anything inside the transmission that he could have changed that would cause the problem.
If you have someone who can help you,  you can check out the outer ends of each shaft. Remove the hubcaps and have your help put the car in gear while keeping the brakes applied. Watch the shaft and nut to see if it moves within the hub while it's shifted from drive to reverse and back.
That would at least tell you if this is possibly where the problem is. It's harder to see the other ends of the shafts, you would have to get the car up off the ground, preferably on a lift.
It could also be a defective shaft. If it was made in China, it's definitely suspect.

Rick

Edit:  There's another thread on here about these shafts that you might want to look at. I don't know how to give you a link to it, but it was just posted to, so it should be at the top of the list.

Good luck to you.

[TJ Hopland]

I will include a link to my thread about issues with the new production shafts for future users:
http://forums.cadillaclasalleclub.org/index.php?topic=161780.0

I can't remember if you can see both sides of the flanges from above or not.   Seems like you can on the left but not the right.   Assuming you can I would put some sort of mark across so you can tell if the position of either flange changes because the shafts will move slightly when you load and unload them so it may be difficult to spot the retaliative change between them without a mark.

My car has always as far as I can remember had a decent clunk going into reverse but this summer seemed to get worse.  Mine seems worse when the transmission is cold.   Hardly notice it when warm.   I forgot to pay attention the one time I drove the car since I replaced the one shaft.   Other than grease starting to escape the shaft assembly felt like it was still in good condition.  The outter which had the bad boot would stay in any position you put it in by itself.  When they are worn they will just flop freely or if they are real bad you can feel slop in them. 

Normally to change the CV's on these cars I pop out the top ball joint and the tie rod.    Since the brake hose is retained by the upper joint nut I also pull the caliper and hang that out of the way and remove the rotor just to save some weight.  Even with all that loose it still takes just the right combination of bending and twisting to get the shaft out of the hub and then another magic combination to get the inner out between the frame and lower control arm.

For the left side I'm not sure how else you would try and do it.  I don't think anyone would try and remove the final drive off the trans,  its got a couple bolts that you can't hardly even see with the engine next to it.   Even if you did remove that I don't see it effecting the shifting since its not part of the trans.   Its like a transfer case with a splined coupling and there are seals on each end so the drive has gear oil and the trans has its atf.   

Right side I suppose you could remove the extension shaft.  I think its 2 bolts to the engine block and one strut.  It splines into the drive so nothing to mess with there.   With that removed I would think you could then slide the shaft assembly out under the engine and save taking the joints apart.   

If he was also doing the wheel bearings you would have to have the knuckles off the car at which point the shafts can just slide straight out that way so no reason to mess with anything further in.

Question for THM400/425 experts, Does the vacuum modulator effect pressures in reverse?  If so maybe check the vacuum line going to it?  No vacuum makes the trans think you are hard on the gas and increases the pressures to firm up the shifts.   That line and unit isn't really close to where the axle flanges are so you would have to go out of your way to even bump into that line.

Since the wheel bearings were done at the same time I really wonder if it was all done correctly.   If this was mine I think I would be jacking up each wheel and giving them a rock and wiggle to see if anything moves.  With everything being new there should be no movement when grabbing the tire at 12 and 6 o'clock.  If you feel any movement there you have a problem.   

I would also check the axle nuts.   If they are original its a 1 1/2" socket.  If they are the new ones its 36mm.   Maybe there is a washer issue and after some use the washer crushed a bit and its no longer tight?    Torque earlier was 150 ft pounds.   The last few years I think it went up to 175? was it?   If you drive very far with them loose it can really tear up the bearings which as you know were not cheap.   

The bearings are pressed onto the hub with a reasonable amount of force then the that is pressed into the hub with a little less force.  There is a bolted on retainer from the outside but it seems like its there as a last resort.   The preload on the bearing set is set at the bearing factory with a shim spacer between the 2 sets so when its pressed together either by a press or eventually by the axle shaft  and nut it should have the proper pre load.     Its not like setting up a rear end where the installer is supposed to be checking shims and preload but you never know these days maybe that detail gets overlooked at the bearing factory.  Seems like I read that the GMC RV people actually do some testing and shimming because with all the extra stress of that setup they need everything to be more than perfect.  They have more weight plus spacers that I think give all that weight even more leverage to stress the bearings.   

I have rolled cars around the shop and on and off trailers with and with and without the engine and trans without the CV axles in em and everything stays tight without the axles holding things together.   I don't think the press fit is so tight that I would expect it to hold under driving conditions without the axle being properly torqued.  Even the new stuff these days is basically the same way except that the bearing races are part of the bolted in assembly.  They are still counting on the axle shaft to keep things pinched together. 

I believe there is still at least one, maybe 2 GMC RV places that will sell you a rebuilt knuckle assembly with grease fittings.  Its not cheap but it should be more than a lifetime fix for a car.   You do have to contact them in advance and tell them you have a car so they send you car one and are expecting a car core back but  The RV's have a different hub. 

[TJ Hopland]

Paid attention today and I would say there is no change in my clunk going into reverse.  Its still much more noticeable when backing out the driveway cold.    Mine is no worse if you go between F and R brakes on off coasting or stopped so what ever is causing mine has got to be in the trans otherwise I would except less change hot to cold and a bigger difference depending on the loading and direction of the drivetrain.