WANTED: DIY removing rear sub frame

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Cooper01
Joined: Tue 29 Apr, 2014 09:06
Posts: 162

  Z3 roadster 3.0i

WANTED: DIY removing rear sub frame

Post by Cooper01 » Mon 01 Jan, 2018 10:26

Hello Zedders!

Does anyone know where I can get a very detailed procedure on removing the rear sub frame? Perhaps even including the torque specs upon reassembly? Yes, I have looked at youtube and a couple of other forums so I have a general idea, but I am looking for those fine details like tips on clamping brake lines, removing everything, bleeding the brakes again and such. :)

I am researching as I will be installing the Ireland toe and camber weld in kits very soon so I will replace all the bushings while I am at it.

Cheers.

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Z3crazy
Joined: Thu 04 May, 2017 14:37
Posts: 38

  Z3 roadster 1.9i

Re: WANTED: DIY removing rear sub frame

Post by Z3crazy » Tue 02 Jan, 2018 12:02

Hi there,

Had a quick look myself and this is about the best description i could find, specifically for the Z3...

http://www.bimmerfest.com/forums/showth ... p?t=174975

Only one photo though, but the text is well written.

Cheers,

Dave
If it ain't broke, don't fix it
Z3 1.9 2000, Cosmos Schwartz

Cooper01
Joined: Tue 29 Apr, 2014 09:06
Posts: 162

  Z3 roadster 3.0i

Re: WANTED: DIY removing rear sub frame

Post by Cooper01 » Tue 02 Jan, 2018 12:17

Thanks. I did see that in my investigation. I have a copy of the TIS and it refers to the table of torque specs but I really do have trouble interpreting it. Thanks for your time. :)

roadvoyager1
Joined: Sun 19 Jan, 2014 18:30
Posts: 69

  Z3 roadster 2.8

Re: WANTED: DIY removing rear sub frame

Post by roadvoyager1 » Sat 13 Jan, 2018 15:37

I did my rear sub-frame last October. I got a summary of the method from Z.org, where Lee and Co. have done several in the Z-shed. I used this as a guide and then documented my daily progress so I could understand how long everything took. This is more of a brain dump at the end of each day rather than a proper method statement but may be useful as it contains the torque values you were asking for. It also records what went wrong, so that may be interesting.
I also bought a second hand rear beam, which I had shot blasted and powder coated before fitting new bushes. This isn't included in my notes, however, the old bushes can be difficult to remove and you may need to call on the services of your friendly local mechanic. It seems most people use a press to remove and fit the bushes.

A couple of points before you start. Check that you can loosen the bolts before you start dismantling the car in ernest.
The push rod plates are held with a cap head Allen bolt which is notorious for stripping, so make sure that the Allen socket is fully engaged (hammered in) before turning it. Access is tight so drilling out is not an option. I got my local mechanic to help and we found applying heat (carefully!!) helped. The threads look to have Loctite on them which may be why they are so difficult to remove. The main bush bolt is very tight and mine had a good coating of rust. I managed to loosen this with a 750mm breaker bar whilst the car was siting on four wheels with the handbrake firmly applied, but it took a lot of effort. Lastly, unless your car has a 2 part exhaust, the exhaust needs to be removed. Again I got help from the local mechanic who applied heat and brute force to get the nuts off (these were replaced with copper coated nuts and a liberal coating of copper grease).
If you can get somebody to help you I would strongly recommend it especially for lifting the sub frame with the diff and axles installed. I did the job single handed and made a dolly for positioning and lifting. It is heavy and very awkward if you are using axle stands. I used a trolley jack under the diff plus a small bottle jack under each end of the beam to get the bushes aligned and lifted.


Rear axle refurb (from Z-org)

1. Remove exhaust from manifold M10 nuts – 16mm socket
2. Disconnect lambda sensors – unclip wires and disconnect connector if required
3. May need to cut off rear exhaust hangers and replace
4. Disconnect activated carbon filter line
5. Disconnect rear brake lines and plug
6. Disconnect hand brake cable from inside cabin and push back
7. Disconnect brake wear sensor
8. Disconnect ABS pulse generators
9. Remove central heat shield. Requires support bracket 1 location.
10. Release ARB support brackets
11. Support trailing arm near hub and unbolt from damper
12. Unplug speedo sensor from rear of differential
13. Unbolt drive shafts from diff flange – M10 Torx head bolts – not necessary
14. Unbolt trailing arms from axle – bolt size? Access? - not necessary
15. Unbolt prop shaft and lower
16. Support diff with jack
17. unbolt diff bearing
18. Unbolt rear beam bush fasteners
19. Unbolt push rod plates and remove
20. and lower diff etc.
21. put wood under hubs to protect
22. red text is my additions




Judge the best balancing point underneath the differential for easy lowering. There are a couple of different types of diffs so it's not always the same position.
Disconnect the ARBs
Remove the bolt through the differential bush
Remove the heat shielding from the transmission tunnel
Slacken off the caliper carriers and caliper bolts (makes life easier when taking them apart on the bench)
Pull the handbrake cables through
Unbolt the prop shaft from the differential (4 nuts)
Disconnect the brake lines
Remove the two plates underneath the rear beam bushes
Undo the 22mm nuts holding the beam on to the chassis
Lower it down slowly to the floor - this is when you know you have the frame balanced on the jack perfectly or not.


My progress log

Sunday 24/09/17 2 hrs

1. Put car in garage and lifted onto axle stands
2. Remove exhaust nuts.
3. Remove cross brace (Note: Should have removed first to give better access for exhaust nuts).

Monday 25/09/17 7 hrs

1. Lift rear of car
2. Remove spare wheel carrier
3. Unclip cables and connectors for lambda sensors from heat shield, separate connectors (marking one set with tape).
4. Remove exhaust
1. Supported rear of exhaust, with jack, just in front of silencer box,
2. put wood under front of exhaust, (with about 1 inch clearance) in front of mid-support bracket,
3. cut through rear 2 rubber hangers, lift weight of exhaust off remaining hanger (on rear axle carrier) and slide hanger from lower exhaust bracket. (exhaust twists to side so may be better supported further back).
4. Lower front of exhaust part way on wood
5. Lower rear of exhaust on jack
6. Pull forwards to front of car until clear of rear axle carrier.
5. Remove heat shield (Note: repair washer required x1 and apply grease to all for re-assembly).
6. Release hand brake cables from cabin end and pull back.
7. Remove rear abs and brake wear sensors

Tuesday 26/09/17 2 hrs
1. Disconnected carbon filter hose
2. Disconnected rear brake lines, capped and plugged.
3. Released ARB support brackets and dropped down.
4. Unbolted dampers from hubs
5. Unplugged speedo sensor
6. Unbolted prop shaft
7. Sprayed realease oil on trailimg arm bushes and diff to carrier bolts.

Wednesday 27/09/17 8 hrs
1. Put jack under differential
2. removed all bolts etc
3. Released rear axle and lowered, (but not in a very controlled manner).
4. Spend about 6 hours removing rust from trialling arms and brake backing plates
5. Treated with aquarust

Thursday 28/09/17 2 hrs
1. Painted trailling arms and brake backing plates with black Hammerite
2. Started to detail design for lifting dolly

Friday 30/09/17 2 hrs
1. Started reassembly of rear axle carrier, differential and trailling arms.
2. Torqued diff to carrier but left bolts for trailling arms loose.


Saturday 30/09/17 6 hrs inc 3 making dolly

1. Built lifting dolly
2. Loaded axle assembly to dolly
3. Positioned axle assembly and lifted, jiggled around a lot and eventually got into correct alignment
4. REALISED I HAVE FORGOTTEN TO TORQUE UP TRAILLING ARM BUSHES
5. Continued to bolt up nearside of carrier to confirm assembly method okay.
6. Waxoyled petrol tank straps, exposed and rust treated edges of chassis plus a few spots.
7. Went for a think on how to do trailling arms........... probably need to drop axle out again. Tbc.

Monday 02/10/17 7 hrs
1. Torqued trailling arm bush bolts to 77Nm. Very tight for space but managed to tighten one click at a time.
2. Final fitted push rod plate to main bolt and side frame on near side.
3. Fitted off side spring and new spring pads.
4. Fitted push rod plate to main bolt and side frame on off side.
5. Main bolt torque 140Nm, push rod side bolts spec 36Nm but 1/4” so tightened to very hand tight with small wrench.
6. Torqued differential bush mounting to 77Nm.
7. Pushed handbrake cables back into position in cabin.
8. Fitted nuts to prop shaft studs and tightened to very hand tight with offset spanner, spec 64Nm.
9. Jacked struts into position, fitted bolts and torqued to 77Nm.
10. Refitted ARB bracketss. Stud for off side sheared when attempting to tighten to 46Nm, so need to drill out and replace with bolt. Nearside tightened to fairly tight only to avoid shearing stud.
11. Clipped hand brake cables into support clips. Off isde clip snapped so will be replacing.
12. Managed to drop link plate for handbrake inside the handbrake trim, between tunnel and carpet????.
13. Refitted hose to carbon filter
14. Cleaned corrosion residues and copper grease from heat shield mounting points. Applied coat of wax oyl to body at contact pints.
15. Refitted heat shield using 8mm penny washers, both side of immediate area around holes coated with Waxoyl earlier and now dried.
16. Plugged in speedo sensor..
17. Fitted rear exhaust support, raised front end partially and supported on wood..
18. Manoeuvred exhaust into position and bolted to manifold down pipe using new gaskets and copper coated nuts with copper grease. Tightened by hand but need to be checked and torqued. Bolted middle exhaust bracket to underfloor support. Fitted exhaust flap valve hose.
19. Fitted exhaust support in front of silencer box

Wednesday 4/10/17 7 hrs
1. Torque up exhaust nuts, used 35Nm as no specific reference in TIS.
2. Refitted lambda sensors and routed cables.
3. Refitted ABS and brake wear sensors.
4. Refitted front X brace, front and rear bolts torqued to 46Nm (with copper grease applied).
5. Used plain washers to connect handbrake cables inside cabin, holding end of cable with long nose pliers to prevent it from turning. Adjusted balance R to L.
6. Reconnect hyd brake pipes
7. Drilled out ARB stud and remounted ARB.

Thursday 5/09/17 1.5hrs
1. Check brake lines for any signs of leakage.
2. Check ARB mount bolt and torque to 38Nm. (not done washer jammed in thread re-tightened))
3. Waxoyl underside of trailing arms
4. refit rear plastic covers


Friday 06/10/17 3.5 hrs (inc 1 hour tidying garage)

1. Sprayed push rod plate securing bolts with Dinotrol wax
2. Fitted new handbrake cable clamp
3. Refitted spare wheel carrier
4. Put wheels back on and lowered car to ground
5. purge brakes of air, continue to purge for fluid change 500ml used
6. Checked main bolt for rear suspension and torqued to140Nm
7. Checked damper to trailling arm bolt when car is on the ground. 77Nm
8. Went for test drive

approx 45 hours (30 hrs spent on mechanical work, 10 rust tremoval, reatment and painting, 3 making dolly and 2 cleaning and tidying)

Cooper01
Joined: Tue 29 Apr, 2014 09:06
Posts: 162

  Z3 roadster 3.0i

Re: WANTED: DIY removing rear sub frame

Post by Cooper01 » Sun 14 Jan, 2018 22:16

You are awesome. Thanks a lot!

Joycey
Joined: Mon 11 Jul, 2011 23:15
Posts: 279

  M roadster S52
Location: Basingstoke

Re: WANTED: DIY removing rear sub frame

Post by Joycey » Tue 16 Jan, 2018 15:28

I was reading through that and thought it looked familiar. Really satisfying job to do at home. Also worth noting the Bentley manual has all the torque values needed.

Lee
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