Upgrading 395 Gearbox with Shorter Ratios & Limited Slip Diff

[GavinT]

Remember that their very tempting crown and pinion sets will turn the other way (I think).

Yeah, I'd want that cleared up but the R12-G had the gearbox behind the engine.
As I say, talking to them would straighten this out. It could well be that they do a number of less common items/mods that don't make it to their more widely publicised 'retail' list.

I'd also be asking if they do a cut 'n' shut of pinion shafts . . . or who might they recommend. 

[jbcollier]

The 5th gear in a 395 is either 0.93 (early) or 0.86 (later).  The straight cut gears on offer have options for 5th down to 1.08.  That’s a hefty rise in rpm in and of itself.  You can use the gears on your existing pinion shaft.  I’d sit down with a gear calculator and work through their options.  It might answer quite nicely.

[Mecky]

Thanks Gavin,

I have now contacted Transconcept. They are not my neighbours, but 500 km is manageable. 4 - 5 k Euros is not exactly cheap, so I won't be able to execute this modification very soon. During the next winter break at the very earliest. Maybe even a year later. I guess, they need my gearbox at their workshop for a few weeks or even months, thus no modification to be done mid-season.

I'll let you know, when they send me a quote or whatever they feed back on my request. I have pretended that my diff is already equipped with the Quaife ATB, thus I hope they reply that it can stay or be re-used after the mod. If not, I'll have to re-consider my preferences on money-spending (and driving more races this season). I'd like to buy a Quaife ATB for my gearbox in July 2022, but if it couldn't be used in the Transconcept gearbox, this money would be sort of wasted.

[jbcollier]

Was mucking about on Aussie Frogs and found the following:

"The 5-speed gearboxes from Romania are labled '365', but their c/p- sets have 395-dimensions, there are two ratios 9*34 as general standard and 8*33 especially designed for pick-ups.
The c/p-ratio of the 395 is 9*34 in general and 9*31 only for R18 Diesel R1344/1354."

If you can find a Romanian 8/33 (4.125:1) it will fit in your 395.

[Mecky]

Hi jb,

great piece of information. I have checked and it's true that the Dacia 1304 pick-up (closely related to the Renault R12) used a 5 speed gearbox, which is called 365 and has a 8/33 diff ratio. The drawings from the workshop manual are the same as in the 395 manual, thus all very plausible. Such a car can be purchased in Romania for less than half what a Transconcept gearbox would cost me. But I think to find a working gearbox in Romania and get it to Germany for reasonable costs, is not easy. I will keep my eyes open, nonetheless. Thank you!

I'm looking forward to the reply from Transconcept. I have already shaped my plans for the seasons 2022 and 2023 around that gear box build. I will trade one or two races this year in order to save the money for the gearbox. I hope they will make an offer soon.
I guess that a good gearbox with useable (hence shorter) 3rd, 4th & 5th gear (top speed not higher than 200 kph) and limited slip diff could gain me around 2 seconds per lap in Zolder. At least I hope so. I only use there 3rd and 4th in the moment. But there are at least three corners, in which my revs fell below 4500 RPM (which is where my torque starts to build massively), but it didn't make sense to shift down, because the steps between the gears are too big. I'd have to shift back up, when I'm still on the outside curb just after I got back on the throttle. And of course the advantage in straight line acceleration would gain me a lot of time.

[Mecky]

After a couple of false starts, Transconcept supplied this info.
My French is nonexistent, so a volunteer for a meaningful translation would be good. 

I have a feeling the Transconcept guys are much like many specialised businesses, Richard Winter being a case in point.
Ya gotta call in and talk to them.

Now, I received the very same two sheet from them. But I'm still not sure, if they took into consideration that my gearbox is different to Alpine A110 and that I don't want to have 5 reverse gears. The price is high, but it seems they offer a real limited slip diff, which I'd prefer over a Quaife Torsen diff. I will try and get confirmed, that they will not sell me five reverse gears. Once they confirm, I'll start to save money. My kind of gearbox will cost at least 6 K Euros. But as you say, the customer support via email is bad. The reply didn't answer anything from my email.

[GavinT]

Yeah, pick up the phone, I reckon, Stefan.
That way, you'll get all the answers in 10 minutes.

[Mecky]

The mounting circle for the 336 transaxles is smaller than that for the 365 transaxles.  That is why they are advertised as for 4spd (336) or 5spd (365).  The 395 uses the same mounting circle as the 336.

The early 395 also has a 0.93 5th.  It is VERY close to the 395’s 4th.

AFAIK, the 369 is more like an NG series than a 3-series so parts will not easily swap into a 395.

Hey jb,
as you are familiar with the Quaife mod for the 395 gearbox, could you please tell me, which pin they mean, when they ask, if I have 5 mm or 7 mm pin diameter? And what if one of them is not in stock? Can I convert one version into the other (e.g. by drilling a Ø7 mm hole, where it used to be 5 mm)? I have not dismantled my diff, yet.

[buzzer]

What might help is sourcing the parts and the knowledge. There is a guy in the UK who specialised in Renault Alpines and Renault 5 Turbos  (the rear engine one's) so he may be useful. contact His name is John Law and in Essex in the UK. I have a Renault Alpine GTA as well and he is modifying my inlet manifold for me at the moment

https://en-gb.facebook.com/jlengineeringuk/
john@johnlawengineering.co.uk

Dave

[Mecky]

I found the answer. They are talking about the pin holes in the splined shafts, which come out of the gearbox on the left and right hand side and get connected to the drive shafts. Quaife only has the 5 mm version in stock, which is right for me. Of course, one could convert a 5 mm pin hole into a 7 mm, if required. That's why it makes sense for Quaife to keep only that one version in stock.

[jbcollier]

Sorry about missing your question.  PM me as well next time.  It wasn’t an issue for me as I’m running a twin link set up and don’t use pins.

[Mecky]

Hi guys, I did buy the Quaife ATB now and it's very easy to fit. @jb: Did you re-use the original differential bolts? Quaife does not deliver new ones with the diff.

I will now do a gearbox overhaul, when it's already open. Not so easy to source all the bearings, as they are quite special. Does anybody here have a list of the bearings used inside the 395 gearbox with detailed description or maybe even part number? I guess, the 365 uses the same bearings. Maybe there is a parts list available somewhere in the interweb.

These are the bearings that I found (diameters of inner and outer ring x width):
- 2 x tapered roller bearings Ø72/35 x 19 mm (differential lateral)
- 1 x cylindrical roller bearing Ø40/17 x 16 mm with retainer ring in outer ring (input shaft at front of diff)
- 1 x double tapered roller bearing Ø52/25 x 28.5 mm with axial contact surface Ø58 and groove Ø48 mm in the outer ring (input shaft rear)
- 1 x needle bearing (needle roller and cage assembly) Ø32/29 x 30 mm (4th gear input shaft)
- 1 x cylindrical roller bearing Ø72/32 x 18 mm with retainer ring in outer ring (front output shaft)
- 1 x double tapered roller bearing Ø67/25 x 30 mm with axial contact surface Ø75 and groove Ø63 mm in the outer ring (rear output shaft)

I'm not sure about all these special names of different roller bearings, but this is roughly what I need. Some of them can be seen in detail on the photos.

[jbcollier]

I reused the diff bolts with no problems though I’m not racing.  If anyone has them, it will be Meca Parts.

There is a Renault transmission parts manual here:

http://lotus-europa.com/manuals/index.htm

Specifically:

http://lotus-europa.com/manuals/misc/r17_trans.pdf

Covers 352, 395 and 365 transaxles from the R27.  I used it to get Renault part numbers and dimensions which I then used to match those on offer from Meca.  The pinion bearing was not exactly the same, different snap ring groove location, but I was able to make it work.

[Rainer]

Be carefull,
The shoulder bearings on my 395 do have different inner diameters, one of them is a special bearing and was hard to source.
If needed i can look up the number and where i ordered it.

Rainer

[Mecky]

Hi guys,

I just wanted to give a quick feedback on my 395 gearbox upgrades.

My preferred 100% solution would have been to bring my gearbox to the company Trans Concept in France and let them put a whole set of new bevel and ring gear, five pairs of gears, bearings, selectors and all the other stuff into my old housing. But this would mean a price in a ballpark between 8.5 and 12 k €. This is even without a limited slip diff. With a clutch type LSD the costs could go up to 14 k. That price is Hewland territory and a bit too much for my budget. Especially after I had serious trouble with my 807 cylindre head. I'm letting a new 1596 cc type 807 engine being built by an Alpine specialist in Germany. That consumes a huge chunk of money, as well.

Earlier this year, I installed a Quaife ATB differential, which was a nice upgrade over the standard (open) diff. From my iteration of data analysis, I found that the Quaife alone helped me gain at least 5 - 6 tenths of a second per lap at Circuit Zolder in Belgium. That's quite a short track (4000 metres) without very long straights. The fastest point is a straight of around 500 metres length, which follows after a quick right hander. With my old gearing, I'm exiting the corner in 4th gear with around 115 kph and accelerate without any upshift to 180 kph, before I hit the brakes. Frankly, the 5th is useless there. I can only use 3rd and 4th gear on that race track. Not really racy.

That's why I have now found a way to make the gears more useable on shorter and slower tracks, while it still allows a high-enough top speed for the fastest track that I race on (Spa-Francorchamps). There is a company in Germany, which is able to manufacture special bevel and ring gears for historic racing cars in small numbers and even one-offs. The cost is ~5 k € for the quantity of 1 pair. I think, it's a 90 % solution for around half the price of the Trans Consept gearbox.
I will now order a 33:8 diff ratio, which should reduce my top speed by 20 kph from 232 kph (5th @ 7500 RPM with my current tyres) to 212 kph. Still a lot for Circuit Zolder, but at least it will give me quicker acceleration through the gears and one more gear to use. The upshift to 5th will be at around 165 kph, a speed which I exceed three times per lap.

I hope, I will be able to improve my best lap at Circuit Zolder (the closest race track to my location) by a significant amount. With the standard gearbox, I reached 1:58.155 min and a theoretical best of 1:57.962. At the same race, my average time was ~1:59. When I can reduce the average to a 1:57 and my personal best to a low 1:56 or maybe even 1:55, I will be in the mix to fight for class wins regularly. I think, the upgrades have the potential to bring me (at least a lot closer) to this target.