Problems with 3.5L / 5spd 265 swap.

CallumNicklin

CallumNicklin

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Hi all,

I have a 3.5L M30 block in my CSI and the 265/6 getrag unit. It also has a LSD fitted to the original diff case. The prop was shortened by the recommended amount (I cannot remember exactly what) and everything fits well.

Since the conversion we have had a problem with the prop breaking CSBs and the familiar ‘thud’ on the underside of the car.

The prop has been checked and correct for balance, and the engine/diff alignment has also been checked and verified.

We have had the car on a ramp, in gear, with the wheels turning and you can see the prop is oscillating.

Can anyone help suggest what more troubleshooting we can try? My mechanic has got estimates for a custom prop, but I just don’t think this is the solution because I haven’t heard of anyone else having to do this.

Many thanks.
 
Loosen the bolts for the driveshaft and guibo (not the tranny flange and guibo) so that there is a slight gap between them. Rotate the driveshaft and observe how the gap changes side to side and/or up and down. Loosen the csb support bolts and move the csb left/right and/or up/down to make the gap between the surfaces consistent as it rotates. The csb bracket holes may need elongating for increased side to side adjustment and/or washers added to drop it low enough to get the ds flange true to the guibo. Once the wobble between the two mating surfaces is corrected then tighten the csb bracket to the body (don’t forget to “preload” the csb) and the ds flange back to the guibo.
 
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Did you actually test by hand yourself the smooth operation of the rear joint?
 
Callum,
Fully agree with the comments above.
What are you using for a transmission cross member? Coupe King or the one that came with the trans? Many people talk of a better result with the Coupe King item.
I’ve just fitted my own 5 speed in the last month. So I have a recently used supplier for the prop work.
PM me if you want to talk it over.
 
are the swivel joints mounted 90° rotated ? they should not be in line i think... mine aren't .
Can't remember IF you can mount the slider wrong ... but i guess yes.
 
Belgiumbarry said:
are the swivel joints mounted 90° rotated ? they should not be in line i think... mine aren't .
Can't remember IF you can mount the slider wrong ... but i guess yes.
Click to expand...

I'm pretty sure you can do it wrong, there should be a mark on each part of the prop shaft that's supposed to line up when the two parts are joined together correctly.
At least my prop shaft has markings, but I don't know if they're original, or from a previous repair and balancing.

EDIT:
Seems like they maybe didn't have any markings from factory as the Autobooks manual in our tech section says to mark the prop shaft before removal. Don't know how accurate that is. But I guess if @CallumNicklin recently had it balanced, it definitely should have markings, old or new.

Screenshot 2021-11-18 at 19.31.11.png
 
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Cornishman said:
Callum,
Fully agree with the comments above.
What are you using for a transmission cross member? Coupe King or the one that came with the trans? Many people talk of a better result with the Coupe King item.
I’ve just fitted my own 5 speed in the last month. So I have a recently used supplier for the prop work.
PM me if you want to talk it over.
Click to expand...
PM’d you.
 
Gransin said:
I'm pretty sure you can do it wrong, there should be a mark on each part of the prop shaft that's supposed to line up when the two parts are joined together correctly.
At least my prop shaft has markings, but I don't know if they're original, or from a previous repair and balancing.

EDIT:
Seems like they maybe didn't have any markings from factory as the Autobooks manual in our tech section says to mark the prop shaft before removal. Don't know how accurate that is. But I guess if @CallumNicklin recently had it balanced, it definitely should have markings, old or new.

View attachment 130563
Click to expand...

Thanks guys. Yeah, all is correctly aligned after rebalancing was carried out.

Can someone confirm if the 2 pieces of the prop require a parallel or non-parallel alignment, or if it doesn’t even matter?

Thank you.
 
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