TRE manual gearbox upgrades.

[Nick Mann]

Yep, getting the preload and endfloat right is something that bothers me too. There are three shafts that need shimming by the right amount. If it was just two shafts both needing endfloat I might give it a go, but three shafts with one endfloat and two preload I'm not so sure about. I shall continue investigating and make a decision, probably based on how much people with experience want to charge!

[adaxo]

As I said b4, count me in, as far its will not cost half of the car value am interested to make standard box run better.

[Nick Mann]

I have no idea as yet as to what the cost will be - I was just interested to hear any other opinions before I chat to them on wednesday about possibility and price.

I will let you know once I know too....

[adaxo]

One more good website, don't know if it was mentioned here or somewhere else(got this all mix up)
http://cobratransmission.com/index.p...c148bf124333f8

[Kenneth]

If your goal is cruising at lower RPM on the motorway, then I would advise just getting a new 5th gear ratio. In my experience the VR-4 drones more at below 3k RPM with a 3" stainless steel (Fujitsubo) exhaust. With a longer 5th (0.72) gear, this was causing more drone at standard speeds as well as the need to drop into 4th on decent hills due to 5th loading up so much the drone becomes uncomfortable.

I wouldn't want to change the final drive unless you plan on significantly increasing engine torque output. Reducing final drive will reduce torque output from the gearbox in every gear.

Having tried a few gear ratio changes, I have settled with 2.785 1st, 1.95 2nd and standard 3rd-5th. I found 0.72 5th frustrated me with gear changes and lack of acceleration more often than I benefited from less than a couple of hundred RPM drop at constant motorway speed.

[adaxo]

Are you change gears by yourself? If yes, how you got that mentioned b4 shims done?, is doable by novice or is more complicated?
Any advice will help to made right decision to DIY or let specialist earn some money.

[Kenneth]

Yes, I do all the work myself.

Shim specifications are in the repair manual. You can look at the Evo ones (essentially the same gearbox) as it is easier to find (especially in English ).
The procedure is also documented and you need to follow it. It takes some time and you need a torque wrench, but is otherwise fairly simple.

[Nick Mann]

Interesting info, Ken. My torque has been measured as an approx 35% increase over stock. The final drive ratio change I am proposing is about 10%. I'm willing to risk it if the cost is not outrageous.
Don't forget that whilst it is illegal to drive at over 70 here, it is normal for people to cruise on the motorway at 80-90 mph.

[Kenneth]

What sort of price would consider outrageous?

I can't say what torque figures my car produces because I haven't taken this one on the dyno. My previous VR-4 was ~360lb-ft and this one runs more boost, less fuel, and more timing advance.
In your case (everyone is different) a final drive change might be well worth it if the price isn't prohibitive. For most, I feel that they would be better served leaving at least 3rd and 4th ratios as they suit common road speeds. (And not by accident)

The question I have is what problem are you trying to solve? If you want to reduce drive train loading then sure, a 3.7 final drive will allow you to do that. You will be ultimately a bit slower and have potentially no difference in top speed (since top speed is determined by power rather than gearing) not to mention the fact that at common road speeds you may find RPM / speed combinations awkward. Which doesn't make sense to me because you make it more awkward on roads which are not at motorway speeds to save a few hundred RPM on the motorway. Usually comfort is compromised for performance, not for a couple of hundred RPM on the motorway...

On the other hand, if you find 1st is useless and want 5th longer, then you can get that without touching the final drive. 4.111 x 2.785 1st gives 45MPH vs 42MPH for 3.68 x 3.333. 4.111 x 0.72 5th only gives you 176mph vs 186mph for 3.68 x 0.72, however the maximum speed is determined by power, so it may not be useful to have 186 theoretical top speed.
Not only that, at 80mph, there is only 200 RPM difference compared to 4.111 x 0.72. (and actually only 350RPM compared to 4.111 x 0.761)


I am not trying to put you off, it is just that I have spent quite a bit of time and money with playing with gear ratios and drive train parts. I would like to think that others can at least get some value from that experience.
I personally like the idea of changing the final drive. I came to the conclusion that I would need more boost (30psi plus) to make use of it, in which case I would need a competition gear set anyway.

[Nick Mann]

To be honest there isn't a real problem with the gearbox. Personally I feel the gearing feels very short. Once driving above about 35 mph it was VERY rare I would use anything other than 5th and unless you are talking about country roads or a motorway slip road, in most other cases 5th would give me enough acceleration to stay with any flow of traffic.

When accelerating hard I felt that the gears ran out too quickly, including 3rd and 4th.
When on the motorway the gearing felt to low again, for example 3500 rpm in an auto VR4 in 5th is closer to 4000 rpm in a manual. My wifes 2.0 Mazda 3 is at 3400rpm at the same speed.

I think the gear ratios are set at good intervals, I don't feel that I spend too little time in just one of them, but I really feel that the total package is geared too low.

As to cost - if it gets to four figures to get the gears machined then I guess I'll have to re-think. I'm hoping a couple of hundred pounds will get me the final drive, then add the costs of the box rebuild. I freely admit I think I am being optimistic!

[Nick Mann]

I should have added that top speed isn't at all in my thinking.

Also, on track, my top speed tends to be in the 120-130mph range. Lengthening the final drive to the 3.6-3.7 range should mean I don't actually need to change gear so much. (As long as I don't feel the urge to then use 2nd a lot! )

[pezza]

Yup, totally agree here, just getting up to motorway speeds from the slip road at maybe 60 - 70, I then reach to find the imaginary 6th gear to cruise but then remember that I am already in top gear and the revs are far north of 3200 rpm. It's not about sitting in the right hand lane all the way, it's more about trying to move with the traffic without feeling you are in too low a gear right in the guzzle zone.

Whilst the VR engine is worlds apart from the LS1 block (285hp 350lb) in the other car at motorway cruise speed, the chevy sits at 80mph just under 2k revs but that that has a ridiculous 2.73 rear axle, (which would be way too low in the VR I know). On a decent run of 100 miles +, the fuel usage is definitely noticeable.

I, too, am probably being optimistic in terms of costing for mods to the gearbox but I guess worth finding out what kinda figure we would be looking at before deciding whether its viable or not.

[Nick Mann]

Okay, latest update:

Redditch gears have a lot of helpful workers but the owner is not a particularly friendly guy! He refused to entertain the idea as he hasn't got the appropriate liability insurance.

The guy who makes my flywheel spacers got me in touch with SP Components, another Redditch based company, who apparently are also involved in racing gearboxes. The guy there says that the project is uneconomical unless we can get to £10k worth of orders. He expects to get approx 20 sets of gears for that. So, please register interest here!! Can people who are genuinely interested in this please let me know ONLY if you are prepared to pay in the region of £500 for a final drive. That cost is only to buy the gears, not to fit them!

[adaxo]

I'm OUT, thanks Nick for sharing your findings,

TBH That is what im after:

Longer Ratios fitted - my thoughts
Well the EVO ratios are now in my car and I've done 200km with them in. This is a follow on from Kenneths post (number 87) on this topic.

http://www.clubvr4.com/forum/showthr...t=21414&page=5

I have attached a little chart showing what the stock is and what I now have. As you can see it is now possible to get to 100kmh in 2nd.

To be honest I couldn't really tell any difference in acceleration between the original ratios and the new ratios. In saying that, my car isn't exactly stock. The only times I really knew that the gears were any different were:

Changing out of second with just over 100kmh indicated on the speedo

After changing out of second being at higher rpm in 3rd gear, making 3rd gear seem much shorter. Before changing out of 2nd at 7000rpm would see you in 3rd at 4680rpm, now after the change the engine is at 5050rpm. This is VERY noticable. When driving at normal aggressiveness levels, ie changing out of 2nd at 4000-5000rpm, 3rd still feels a lot shorter and feels...for want of a better word, 'sportier'. This is the biggest change imho.

Now for the longer 5th, which is the original reason I started to research different ratios. I couldn't notice anything when driving in 5th. The revs are obviously a bit lower, but there was no difference in acceleration, pickup or lag that I could notice. I still ended up on the high side of 100mph passing 5 cars while keeping it in 5th the entire time. Apart from looking at the tacho there was no real way to tell. What I didn't notice however was that changing from 4th to 5th feels different. Changing at 70kmh isn't really an option when accelerating onto the motorway or another situation where you need to accelerate as quick as other cars, you need to be at about 85kmh or so to change into 5th now, otherwise the car does sound like it is being bogged down a bit. In saying that when in traffic on the motorway I regularly changed into 5th at 60kmh and just let the car build up speed which it did perfectly ok, without roughness or anything. I think that out on the open road going up hills where you'd normally be able to keep it in 5th gear down 95% of the time, you might need to change down into 4th a bit more.

Overall I really recommend the ratio swap. 1st is still simply frantic as always even though it is a lot longer, but the main advantages are what I highlighted above, the longer 2nd that lets you get to 100kmh, the effective shortening of 3rd gear and the longer 5th for lower cruising rpm.

copied shamelessly from here

[Kenneth]

£500 is a very good price for the complete final drive. I would be keen depending on some answers

Will they be helical or straight cut? (straight cut will reduce thrust load. Probably not a problem with standard turbos, but if you are going to spend the money....)
What will be the torque limit of the final drive?
Any idea of approximate weight? I would hope that they can get it somewhat lighter than standard...

Will they all be the same ratio, or can we get variation? I am really only interested in 3.2:1 (pretty much sets up all common speed limits at ~2750RPM and a big 5th)

[zentac]

there are loads of companies out there that could make you a final drive, that already make straight cut gears for EVO's. ppg, albins, liberty, drenth, eliteracingtransmissions, quaiife, etc.. etc..

Im going with a ppg box for next year.

[Kenneth]

Not for ~£500. PPG final drive is $2200 AUD, Drenth is not much dissimilar and it won't work with standard input shaft and gears.

[Nick Mann]

£500 is a very good price for the complete final drive. I would be keen depending on some answers

Will they be helical or straight cut? (straight cut will reduce thrust load. Probably not a problem with standard turbos, but if you are going to spend the money....)
What will be the torque limit of the final drive?
Any idea of approximate weight? I would hope that they can get it somewhat lighter than standard...

Will they all be the same ratio, or can we get variation? I am really only interested in 3.2:1 (pretty much sets up all common speed limits at ~2750RPM and a big 5th)

They would all need to be the same. 3.2:1 is a loooong gear, Ken? I was thinking about 3.6:1. Potentially helical cut - straight cut makes it tricky to avoid a whine. People are quoting £2000 up for a one off, it's the setting up of the machining that costs the big bucks apparently, so multiple units brings the costs down massively.

The guy is unwilling to spend any time working on specifics unless there is genuine interest to get the project off the ground. TBH I would expect that it will be easy to sell 20 units in the long term, but I don't have £10k to pay for them up front!

[zentac]

you want 51/14 = 3.6428571428571428571428571428571 that will fit perfectly, I've done a hell of a lot of research into mitsi gearboxes

you best off the shelf options are either tream rip (tre) who do a 3.735:1 or sheptrans who do a 4.11:1 - arnside stock the 4.11

Also Glebe did custom one off stuff for me so it may be worth a chat.

also I read in an earlier post you were thinking about shimming the box? why is that?

[Kenneth]

you want 51/14 = 3.6428571428571428571428571428571 that will fit perfectly, I've done a hell of a lot of research into mitsi gearboxes

you best off the shelf options are either tream rip (tre) who do a 3.735:1 or sheptrans who do a 4.11:1 - arnside stock the 4.11

Also Glebe did custom one off stuff for me so it may be worth a chat.

also I read in an earlier post you were thinking about shimming the box? why is that?

Why would we be interested in a 4.111 final drive when we have that as standard?!

Obviously we don't want off the shelf, otherwise we wouldn't be talking in this thread

There are shims on the input, output and centre diff which are used to set the preloads (in the case of the output shaft and centre diff) and end float (for the input shaft). The shims are important to get right or the gearbox will fail prematurely. You can re-set the shims based on your performance goals. For example if you want more reliability at high torque inputs, you can increase preload. You will reduce bearing life but increase high torque shaft stability.

They would all need to be the same. 3.2:1 is a loooong gear, Ken? I was thinking about 3.6:1. Potentially helical cut - straight cut makes it tricky to avoid a whine. People are quoting £2000 up for a one off, it's the setting up of the machining that costs the big bucks apparently, so multiple units brings the costs down massively.

The guy is unwilling to spend any time working on specifics unless there is genuine interest to get the project off the ground. TBH I would expect that it will be easy to sell 20 units in the long term, but I don't have £10k to pay for them up front!

3.2 IS a long gear. It essentially means starting from the standard equivalent of 2nd, which isn't difficult even with a light weight flywheel. I wouldn't want to be stuck behind stop start traffic on a steep hill, but hey.

As I said before, changing the final drive changes the road speeds at which you do gear changes as there is a minimum RPM you will need or the engine will make horrible noises if you try and accelerate at anything beyond a crawl.

Using 3.6, you will change the ~3000RPM common road speeds down to 2500RPM (per gear) where acceleration will be relatively poor. Your alternative will be to drop a gear but then your RPMs will be unnecessarily high and you will have that motorway feeling all the time.
3.2 on the other hand, re-aligns the first couple of gears to sit around 3000RPM in a low gear and if you want to cruise at low RPM, you can still change up.

Given a 3.2 final drive, I would be changing my 5th gear for the 0.857 ratio (if I can find it at reasonable cost.) because 350kph is a bit un-realistic.