Quaife ATB differential

The axle ratios have to be the same because in 4 wheel drive the output shafts to both axles rotate at the same speed. Gear ratios are a matter of interest for engine performance and vehicle weight only.
I emailed Eaton to discuss certain points and they confirmed that the Trutrac can be fitted in a front axle because it isn't a fully locked diff.
Back in the sixties it was usual to fit a disc style LSD in the diff. of a Mini for serious Rally driving. Some went as far as to increase the pressure loading on the plates but this increased the steering effort and was for strong men only!

Roger

So some casual googling over weeks tells me that axle ratios can change from one model to the next. If the Axle ratio the ATB LSD is made for is different will it mean the unit is incompatible with my car? For ex: for 3.73:1 vs 3.14:1 vs 4.11:1 diff's? This would mean different count of teeth in the gears - would it still work?

The axle ratio is a feature of the crown wheel and pinion. The crownwheel bolts onto the differential, so the ratio of the differential is determined by whatever crownwheel is bolted to it. In the case of the Quaife and any other aftermarket differential, they come as a diff only. You bolt your existing crownwheel to it, thus keeeping whatever gear ratio you already have.

To that extent, the issue of differential ratio is irrelevant to your situation. All you need to know is if the differential unit is the same in your axle as in the Jimny. The rear differential unit Suzuki use in the 2018 Jimny has been unchanged for decades. They are all the same from the SJ413 (possibly also the 410?) to the current model. They are 26 spline, 10 bolt.
At the bottom of this page is a list of all vehicles that use this same type of diff. The list is for an ARB air locker, but the quaife unit will be compatible with all the same vehicles. www.devon4x4.com/airlocker-suzuki-26-spl-10-bo.html

To answer your other questions, yes the driveshafts are strong enough. Fitting a second LSD in the front axle will only have an affect on driving when you are in 4wd. In my experience, the handling in 4wd is already biased towards understeer and I'd guess a front LSD wouldn't change that much.

Busta wrote: The axle ratio is a feature of the crown wheel and pinion. The crownwheel bolts onto the differential, so the ratio of the differential is determined by whatever crownwheel is bolted to it. In the case of the Quaife and any other aftermarket differential, they come as a diff only. You bolt your existing crownwheel to it, thus keeeping whatever gear ratio you already have.

To that extent, the issue of differential ratio is irrelevant to your situation. All you need to know is if the differential unit is the same in your axle as in the Jimny. The rear differential unit Suzuki use has been unchanged for decades. I they are all the same from the SJ413 (possibly also the 410?) to the current model. However there are some differences in the front differentials.

Thank you for responding. So as long as my axle is 26 splines 6.9" gear its all good? Or is the Axle shaft diameter also important? For example corresponding to this diagram does my Axle shaft diameter have to match D4? ATB LSD Spec Diagram

Overall the specs have remained the same to similar across the years but I am apprehensive some some minor spec change in parts might make it incompatible, hence I am double-triple-checking things before I import the unit at great cost.

I've edited my post above with more information that should answer your questions.

I understand now. The Diff attaches to the Crown which is driven by the Pinion and it does not matter what the ratio is. I think I am fairly confident now. I will post pictures of the installation a few weeks later once It arrives.

I was struggling with a beginners confusion - being a non-engineer, on this topic - but some things seem to fall in place now. Thank you for the patient replies.

Cheers

Ordered the unit today. Looking at the blow-up diagram : Gypsy Parts Catalogue

I see a left Diff Left No.21 and a right Diff Right No.23

So I have to remove the unit on the left No.21 and bolt it on?

G0bble wrote: Ordered the unit today. Looking at the blow-up diagram : Gypsy Parts Catalogue

I see a left Diff Left No.21 and a right Diff Right No.23

So I have to remove the unit on the left No.21 and bolt it on?

From the gypsy parts link this is what it means to your situation:

Parts 15-20 and 29 & 30 are all internal parts (spider gears, countershaft and seals).

These internals go inside parts 21 (body) and 23 (lid).

All these parts as a whole will be removed and replaced with the Quaife or an ARB or a Kaiser as you choose. So with the diff out of the axle you undo the bearing carriers and swap over the bearings and crown wheel to the new part, put back together and set backlash. Pretty simple really.

Riccy wrote:

G0bble wrote: Ordered the unit today. Looking at the blow-up diagram : Gypsy Parts Catalogue

I see a left Diff Left No.21 and a right Diff Right No.23

So I have to remove the unit on the left No.21 and bolt it on?

From the gypsy parts link this is what it means to your situation:

Parts 15-20 and 29 & 30 are all internal parts (spider gears, countershaft and seals).

These internals go inside parts 21 (body) and 23 (lid).

All these parts as a whole will be removed and replaced with the Quaife or an ARB or a Kaiser as you choose. So with the diff out of the axle you undo the bearing carriers and swap over the bearings and crown wheel to the new part, put back together and set backlash. Pretty simple really.

Ok that was useful - I haven't quiet finished reading the beginner textbook on drivetrains so please correct this non-engineer novice, if I am wrong - (and I am only going by all the Youtube videos I have seen so far).

1. Can a slight mm variation in dimensions/size of the new LSD (compared to Original) change the existing backlash settings for the Crown/Pinion when I fit it in?

2. How exactly do I adjust backlash when (No.29,30) are going be self-contained inside the LSD?

3. After I adjust the backlash do I need to readjust the preload on the Pinion using Shims (No.4)? (which ideally I would not have touched when removing the original diff)... Meaning should I go in armed with extra shims to add (if not remove) be safe? (On the side - is it right that the MG413 appears to use a fixed collar (No.3) and shims (no.4) for preload unlike the UK Jimnys that use crushed collar)?

4. If I need to adjust the Shims (No.4) on the Pinion - will I need to remove the propeller shaft and place the diff on a table to now adjust both preload and backlash in turns iteratively using a DTI Dial indicator and a fish scale (measure and repeat until the right values are attained)? Which means I need to find the right value ranges for the MG413 which will be different from the Jimny and Samurai... and then also only go after finding a fish scale (not a weight scale looks like)? Also it looks like there is a fitment with a string required to be bolted to the pinion flange on Suzukis before force can be measured accurately - which I need to check if the Garage is going to have... (not even sure if the MG413s need this or it was only for the UK Jimnys)

5. Like in the diagram - Do I open the LSD and place the "cap" on one side of the crown gear and bolt it into the other side through the threads in the Crown gear ( joining (No.23) and (No.21) in the diagram)?

6. Some videos I saw (and it makes sense) recommended replacing brand new bearings rather than reuse old ones. My car has done +80k kms already and I would rather replace the bearings (No. 25,26). What are your thought on this? If the answer to (Q.3) above is Yes then also replace (No.6)?

I have a problem with this situation. Asking questions of this nature indicates to me that your knowledge of how a diff. works and what parts of a diff. are retained when you replace the diff. unit itself are limited and that you will be better off entrusting the work to a specialist. This statement is not to be taken as a condemnation of your ability or your desire to do the job properly, but you will be spending a lot of money to buy an LSD and I do not want you to be disappointed with the result. You are now talking about replacing the crush tube on the pinion shaft and that requires specialist knowledge and great care to ensure that the correct preload is obtained. Get it wrong and it's a strip down, a new tube and start all over again. I strongly recommend that you entrust the work to a specialist who will warrant their work. Peace of mind will be worth it.

Roger

Hey Folks,
Yes - Your assessment is correct. And for the record, I was never planning to do it myself. I intend to go to a garage to get it done. This is not a DIY project.
I am merely trying to visualize and confirm the correct procedures to follow including worst-case because I want to supervise the work and catch the situation if and when a garage mechanic takes a short-cut.

Let me explain the challenges - The situation here is India is that anybody with proper technical training and a polytechnic education is going to be employed in an automotive manufacturing plant at some remote factory location (India has a decent sized manufacturing hub) and hence the right kind of skills combined with proficiency is not available with the usual mechanics at local garages. I can find a 100 mechanics nearby who will fit an axle assembly and hammer things in, know how to pressfit a bearing and do all the labor work for me, but that is not what I searching for. Even the A.S.C run by Suzuki India do have well trained staff according to Japanese management principles however they mostly just want to do replacement of throw-away parts and routine servicing and do not entertain modders who want to pimp their car ( I have seen myself how they sweat it out to finish their assigned work on time and juggle workloads across cars due to the sheer work volume for routine servicing, and I can't blame them). Hence if they find out something in the axle is off they are more likely to order another part assembly and throw it in and let the car owner pay for the parts and generate sales, rather than repair the existing parts by applying proper engineering skills. I spoke to a few garages locally and nobody has a DTI dial indicator. The reply was that "we are just removing and replacing the diff component and so nothing should change in backlash... correct assembly was already done in factory". Asking them to measure backlash or the run-out on a flange is like above their pay-grade. Although if trained they could very well do it and with all the proper equipment supplied by the multinational business owners, this expertise and proficiency is unlikely to be available in a garage shop at a location convenient for me.

As I indicated earlier - I am not an engineer either, hence my incessant questioning around this as a means of attaining more mental clarity on these mechanical engineering aspects I have never dealt with before in my life. I could simply walk-in to a garage as a "customer" and get the thing fitted without anything being measured, but anyone here would realize - its not the right way and I dont want to do it that way. This is also a learning hobby that I find stimulating - and I want to be there and handle the DTI and inspect the readings while the mechanic does what he is proficient at. I am still searching for that garage with an Engineer-Mechanic not just any Mechanic. So far simply make phone calls and asking questions like "Do you have a DTI dial indicator to measure blacklash..?" is looking to be a futile exercise. I am having to visit every garage personally, but I am at it.

On another note - Labor is extremely cheap in India compared to the West hence the DIY culture and hands-on engineering expertise from car owners is lacking. Like people do shopping in the west because "its good for the economy" - we get our work done from others (and with a feel-good factor) because it feeds hungry mouths and families of the employees or labour professional. However the technical education levels and English can be another challenge when dealing with projects like these. For the same reason - the Indian Automotive forums with 100s of members pan-India are practically useless to me when it comes to getting specific technical questions answered - few people have actually "been there and done that" before with the actual experience but gigantic ego's about being "Engineers" are rampant.

Thank You All for your patient replies as always.