BMW/Titan LSD Viability

[Geoff Brown]

On 01/11/2023 at 10:47, ScottR400D said:

“When the prototype TITAN Mk2 is available maybe I could assist in some back to back testing. Well I do have a Tracsport BMW Diff so what better comparison. Obviously I did not turn down the invite”

Any news on that front Geoff? 

Unfortunately no, but I am not holding my breath. Maybe I will drop 'Uncle Bob' a line in the New Year.

Oh & for all those who appreciate a decent LSD lovingly prepared by Steve at SPC, three years & 6000 miles later the break out torque is still 25 ft/lbs. Same as the day it was fitted. 

 

[GulfSeven]

Interesting the break out torque is so much lower than the Titan. I'd have thought there would be an ideal torque for the car?

[ScottR400D]

Everyone I know with a Tracsport has had the same experience. Start off around 25, perhaps lose a ft.lb. or two in the early days then stay steady. I’ve also done  6k or so but Nigel Brown has done 2 or 3 times that with the same result. 
 

The only reason for the Titan to start off so high is to allow for steady and continuous degradation, as far as I can see. 

[GulfSeven]

That doesn't make sense. If that was the case they wouldn't perform well at 45 or whatever when new.

[ScottR400D]

8 minutes ago, GulfSeven said:

That doesn't make sense. If that was the case they wouldn't perform well at 45 or whatever when new.

They don’t, in my experience. The reason I changed to a Tracsport, in addition to having no faith in the longevity of the Titan, was the awful grunting, graunching and other horrible noises made by my expensively rebuilt Titan at lower speeds.  

[Geoff Brown]

23 hours ago, GulfSeven said:

Interesting the break out torque is so much lower than the Titan. I'd have thought there would be an ideal torque for the car?

25 ft/lbs IS the 'ideal' torque as set up by Steve Perks during build. I would imagine that the lower torque value is because the SPC LS unit has Molybdenum faced discs unlike the 'chocolate' carbon or sintered facing.

The higher torque setting for the Titan is to compensate for bedding in & a greater rate of wear in use.  Remember that Titan recommend an overhaul every 10,000 miles for a road car or until the break out torque reaches 20ft/lbs. This period equals about 3 to 4 years of driving with the odd TD here & there.

SPC do not recommend any overhaul interval due to the unit longevity. The only recommendation is fit a mag plug, monitor it & change the oil regularly - about every 2 to 3 years. Steve had one of his 'prototype' LSD fitted to a racing Seven for 4 years. When dropped after that period on inspection the internals looked brand new. So in a road car with the odd TD here & there at a guess I would say that the LSD could last longer than any ownership period unless of course there was a mechanical catastrophe of some sort.

[GulfSeven]

1 hour ago, Geoff Brown said:

The higher torque setting for the Titan is to compensate for bedding in & a greater rate of wear in use.  Remember that Titan recommend an overhaul every 10,000 miles for a road car or until the break out torque reaches 20ft/lbs. This period equals about 3 to 4 years of driving with the odd TD here & there.

I'll check the torque again this winter. My 310R is 4 years old now and has done 7,000 miles / 8 track days. Last winter when I checked it was still 42 ft.lbs though (the same as when it was new).

I'll report back...

Edited November 5, 2023 by GulfSeven

[Geoff Brown]

6 minutes ago, GulfSeven said:

I'll check the torque again this winter. My 310R is 4 years old now and has done 7,000 miles / 8 track days. Last winter when I checked it was still 44 ft.lbs though (the same as when it was new).

I'll report back...

 

Edited November 5, 2023 by Geoff Brown

[Geoff Brown]

6 minutes ago, GulfSeven said:

I'll check the torque again this winter. My 310R is 4 years old now and has done 7,000 miles / 8 track days. Last winter when I checked it was still 44 ft.lbs though (the same as when it was new).

I'll report back...

Your Titan has done well then. Long may it last......

[GulfSeven]

2 minutes ago, Geoff Brown said:

Your Titan has done well then. Long may it last......

I had the oil changed to RRT at the start of year service this year. Other than that I've just checked the torque annually.

[StevehS3]

The sintered plate type should last much better in a 1.6 with 152hp.
Having said that I wouldn’t fit another Titan. I didn’t like the clatter and the service interval is completely unappealing to me. Also, there is no getting away from the design flaws such as over-flexing of the Belleville washer. 

[ScottR400D]

18 hours ago, StevehS3 said:

The sintered plate type should last much better in a 1.6 with 152hp.
Having said that I wouldn’t fit another Titan. I didn’t like the clatter and the service interval is completely unappealing to me. Also, there is no getting away from the design flaws such as over-flexing of the Belleville washer. 

You’re right, premature failure seems to be more of an issue with higher power cars, often occurring at 3-4000 miles or so. 

The noises under ‘normal’ operation though are common across the range. Some find that is acceptable and live with it. Or find that it’s alleviated with an oil with a high level of friction modifiers but that’s just masking the real issue.

I tried the RRT oil (and others) but didn’t find it made that big a difference, though some clearly do. 
 

 

 

Edited November 6, 2023 by ScottR400D

[aerobod - near CYYC]

The biggest difference to noise on my Titan diff was to change to 75W140 oil (Red Line in my case), it is fairly quiet with the sintered plates with that oil. Although I achieved over 30,000km on the original carbon plates, I'm now at about 10,000 mainly track km where the initial preload was set to 50Nm with new sintered plates and has now stabilised at 40Nm after a couple of years of use.

[Geoff Brown]

On 05/11/2023 at 14:11, GulfSeven said:

I had the oil changed to RRT at the start of year service this year. Other than that I've just checked the torque annually.

A good oil to use in the Diff even if it does have certain additives to keep the Diff quieter. I use Castrol B373 SAE 90 GL5 which is 'old school' mineral oil for LSDs but it performs well. None of this multi grade stuff packed full of additives to make the LS unit work better & quieter. Allegedly.

[BigCol]

Steve Perks swapped my FUBAR Titan unit for one of his TracSport units last year.  However, whilst it functions perfectly, the diff is still noisy.  Years of the crown wheel and pinion being in an abrasive carbon goo have obviously taken their toll.

I have tried using Red Shockproof oil as Steve suggested but that hasn’t masked the noise.

Steve says that replacing the CW&P isn’t viable, so I am now going to follow what many here have done and get a new, open, diff for Steve to swap his unit into.

Caterham has stock but at 💰💰💰; it also comes with carrier etc that I wouldn’t need.

Has anyone bought a unit from BMW and “adjusted” its case to match/fit a 7?

I wouldn’t mind breaking out the angle grinder/disc cutter (and I’d have my current diff as a pattern) if it was to represent a significant saving.

Edited November 11, 2023 by BigCol

[ScottR400D]

Have you found a source of the same housing that CC use? I believe there are variations on the BMW ‘168’ diff. 

Other than that the housings appear to be fairly precisely machined for a 7 might not be easy to get accuracy with an angle grinder! And of course you’d need to be sure the CC backplate fitted the housing. 

I assume you have a 3.9 ratio diff? I have a spare, rebuilt 3.6 with a Titan which I’d sell to you for a lot less than CC will charge but it’s no use if it’s the wrong ratio of course. 
 

You could always buy a diff from BMW and strip out the CW and P, I guess. 

Edited November 11, 2023 by ScottR400D

[aerobod - near CYYC]

Hi BigCol,

There are several areas of the 168K/L/LW casing where machining is just to remove extraneous protrusions near the rear cover to match with the Caterham cover, machining there isn’t precise. The critical bit of machining is the two front mounts where the forward facing “wings” with mounting holes are removed and the casing is machined to the width of the Caterham carrier and the two M12 holes are drilled and tapped into the side of the casing to match with the carrier mounting holes.

Also, the 168K/L/LW diffs came in quite a few ratios, only a few are 3.64:1. There are some sources online for the 3.64 CWP,  bearings, seals, appropriate thickness circlips and crush washer to do a rebuild in your current casing.

You may also just be able to re-shim your existing CWP to reduce noise. If the only effect of the carbon “slurry” is to polish things as opposed to introduce scratches or gouges, then new side bearings and difference thickness circlips can optimize the mesh and backlash, plus new seals as the old ones are destroyed accessing the circlips. The front bearing replacement is a bit more involved with the precise crush washer fitment, but the slurry is less likely to have had an effect on it, as it doesn’t get as much oil splash.

Edited November 11, 2023 by aerobod - near CYYC

[PhilT]

Hi all, thanks for this thread. I'm looking at 2018 420R with 9k miles next week and I'm keen to check the diff condition. I've taken notes from this who have shared their knowledge on here (thank you) plus the info found in the link below: https://caterham420detailedbuildblog.co.uk/2020/10/18/differential-preload-check/

If the diff is below the 20lbft mentioned what cost should I expect to service the unit? 

Thanks for your help! is there anything else I should be aware of that won't immediately obvious?

My first post as a new member (or a returning member after 20yrs) once I find the Cat I want I look forward to joining you all on some outings.

Phil

[ScottR400D]

13 minutes ago, PhilT said:

Hi all, thanks for this thread. I'm looking at 2018 420R with 9k miles next week and I'm keen to check the diff condition. I've taken notes from this who have shared their knowledge on here (thank you) plus the info found in the link below: https://caterham420detailedbuildblog.co.uk/2020/10/18/differential-preload-check/

If the diff is below the 20lbft mentioned what cost should I expect to service the unit? 

Thanks for your help! is there anything else I should be aware of that won't immediately obvious?

My first post as a new member (or a returning member after 20yrs) once I find the Cat I want I look forward to joining you all on some outings.

Phil

The cost of a rebuild varies. If the bearings are OK maybe £4-500. If the whole lot needs renewing, twice that or more. I was charged over £900 for a full rebuild back in 2020. 

Plus the cost of removing and refitting the diff if you can’t do it yourself. 

At 9k/5 years I’d be having the diff rebuilt regardless of the preload. 

[PhilT]

1 minute ago, ScottR400D said:

The cost of a rebuild varies. If the bearings are OK maybe £4-500. If the whole lot needs renewing, twice that or more. I was charged over £900 for a full rebuild back in 2020. 

Plus the cost of removing and refitting the diff if you can’t do it yourself. 

At 9k/5 years I’d be having the diff rebuilt regardless of the preload. 

Thanks ScottR400D.

Edited November 11, 2023 by PhilT

[StevehS3]

Is a 2018 car likely to be carbon or sintered plate? 

[ScottR400D]

Sintered. 

[BigCol]

17 hours ago, ScottR400D said:

Other than that the housings appear to be fairly precisely machined for a 7 might not be easy to get accuracy with an angle grinder!

17 hours ago, aerobod - near CYYC said:

The critical bit of machining is the two front mounts where the forward facing “wings” with mounting holes are removed and the casing is machined to the width of the Caterham carrier and the two M12 holes are drilled and tapped into the side of the casing to match with the carrier mounting holes.

Thanks chaps - naively, I thought the Caterham casing is the BMW one less a few, easily removed, lumps and a different backplate!  Does rather explain why this doesn’t seem to have been suggested before!

Back to Plan A… 🤔

[Geoff Brown]

22 hours ago, BigCol said:

Steve Perks swapped my FUBAR Titan unit for one of his TracSport units last year.  However, whilst it functions perfectly, the diff is still noisy.  Years of the crown wheel and pinion being in an abrasive carbon goo have obviously taken their toll.

I have tried using Red Shockproof oil as Steve suggested but that hasn’t masked the noise.

Steve says that replacing the CW&P isn’t viable, so I am now going to follow what many here have done and get a new, open, diff for Steve to swap his unit into.

Caterham has stock but at 💰💰💰; it also comes with carrier etc that I wouldn’t need.

Has anyone bought a unit from BMW and “adjusted” its case to match/fit a 7?

I wouldn’t mind breaking out the angle grinder/disc cutter (and I’d have my current diff as a pattern) if it was to represent a significant saving.

Having had my Diff overhauled by Steve I am surprised he could not set up the CWP instead of replacement, which for whatever reason he cannot.

I had the carbon/oil soup which rendered all the service items useless so Steve had to completely rebuild the diff from scratch with new bearings, seals clips & shims. He set up the CWP, which he said only had a slight polish on it. It is virtually silent. 

 

 

 

 

 

 

[GulfSeven]

On 05/11/2023 at 14:01, GulfSeven said:

I'll check the torque again this winter. My 310R is 4 years old now and has done 7,000 miles / 8 track days. Last winter when I checked it was still 42 lb.ft though (the same as when it was new).

I'll report back...

Okay, update time...

Two things have changed since last year - firstly the diff is now full of RRT oil, and secondly I have a new (calibrated) torque wrench. Anyway, today's test showed a breakout torque of 38 lb.ft. Has it actually dropped by 4 lb.ft? I'm not sure. It could equally be the oil or it could be the torque wrench. Next year's test will be with the same oil and torque wrench so we'll have to wait and see. Either way, 38 lb.ft is fine for now.

Edited November 12, 2023 by GulfSeven