Which Renault gearbox was most commonly used by GTD?

My car was supplied as a complete kit by GTD in 1991. The gearbox has had the identity tag removed & the receipt does not specify which version of the Renault was supplied.

Which was the most commonly supplied box?

I's like to know what ratios I'm running, all of which are detailed in Ken Saunders site; http://www.gt40club.clara.net/technics.htm

Once I know which version of the 'box I'm most likely to have I can go form there...

Any suggestions greatly appreciated!
Julian, it is most likely that your gearbox is a Renault 30 (3.88 diff). We now almost universally use the R 21 or 25 box with 3.44 diff. with considerable internal modifications, including the Quaife ATB LSDiff. etc. and rod gearchange mechanism. Contact Chris Cole at Mach1 TRANSMISSIONS (01952 222155) with details of your box and he will advise you. Look for casting numbers on the casings etc. Frank
Julian, If you send me a pic of the rear gearbox housing, i can tell you what you have. At the time (1991) you could have been supplied either gearbox. Though its likely to be the R30. A pic will tell me for sure. I stock modified R21 gearboxes with better ratios or stronger export gearboxes for higher hp engines. I worked for GTD from 1988 through to 1994 and have been supplying parts for GT40 guys for the last eight years. You can E-mail the pics I will reply once ive confirmed what you have.

All the best

Thanks Frank & Mark, I'm sure you're both right in it being an R30.

From that I've calculated the car is doing about 120 mph @ 5000 rpm in 5th gear, which sounds about right to me, compared to how the car drives....

I'll keep your details for when I upgrade the 'box, altho it'll be sometime in the future!

Robert Logan

Defunct Manufactuer - Old RF Company

I fully agree with the above but I think that Renault 20 boxes that were 4 speed were also popular (price) in that time also.

I do not believe they were supplied by GTD at that time but some complete factory supplied kits are not so complete and things like engines and gearboxes were supplied privately. There was a tag with 369 on it with my R30 box I first used but I would expect that this is well gone.

Best wishes,

Julian, I would say the odds are pretty high that your gear box has a first gear of 3.36, second of 2.06, third of 1.38, fourth of 1.06 and fifth of 0.82. The odds are about even that the diff ratio is either 3.88 (the older boxes) or 3.44 for the newer ones.

Howard Jones

This is just what I wanted to know! I am fairly sure that I have a R21, I counted the revolutions in 5th gear and more or less came out 3.0 or so on the output shaft. anyway can this thing take about 350hp from a 302? The clutch is already upgraded by centerforce. How much of an improvement can be had with mods? how much money for mods. Would consider a tradein, mine has never been run.
Howard, we have many cars running 350hp+ in UK, including in competition, so dont worry about your box, although all such mechanical things can break at times, usually at the most inconvenient times. Frank



The renault boxes can take 350 bhp. That is what mine has done for the last 24000 miles. With sprints and hill climbs the car gets many rough launches off the line. Doing that I have never broken the box. Overtaking a car on the Silverstone by pass some years back I stripped the input/primary shaft spline but that was thought to be caused by a misalignment in the adapter plate. Don't ever jack your car up on the adapter plate!!!!

However I have broken about 4 AP race cluthces (the springs pop out) and a Jack Knight driveshaft (we did 60 1/4 miles in one afternoon prior to the Speed Trials to get Wendy up to speed!). Surprisingly broken no CV joints yet but I leave that to others who have an appetite for them. On the clutches I have had a "AP" special made that is a solid clutch with no springing in it at all. It coped fine at Goodwood last Saturday.

Chris Cole at Mach One Transmissions can (I beleive) supply a recon box at about £700 to £750 (no vat) plus carriage. I think he puts a 3 month warrantee on his work but you need to check.

Personally I would recommend Kevin Jones of GTO Engineering based near Reading, Berkshire. Kevin is the person who had Quaife make the LSD that everyone likes. He is where they all come from at £650 each. He personally runs a Renault Alpine in competition so has a stake in getting good parts designed for the renault box. As I have posted elsewhere he is working on a full set of Quaife gears (6 speed) to replace every gear in the renault box that should be available sometime next year. Cost was expected to be about £3500 to £4000 for the parts. Less than half the price of a full Quaife box or proper ZF.

Kevin thinks we are all mad using Renault boxes on 302 engines but he watches with interest and amusement!

He is not as cheap as Chris Cole so you pays your money and you takes your choice.

The other Quaife internals are an upgraded 1st and 2nd gear with larger diameter input and primary shaft. There is no spline on this as it is a one piece shaft. Mathematics says it should be about 4 times stronger than the renault items. It raises your gearing in 1st and 2nd by I think 12% approximately. To fit this item apparantly costs about £1500. That is if you can get the parts as the original batch has been all used up and Quaife will only make a batch and not individual shafts, as far as I know. I may be wrong on that so talk to Quaife. I also think that the copyright on this design belongs to someone other than Quaife so you may need permission there too.

As to final drives, if you don't have any quaife bits or just the LSD I would suggest the 3.44 ratio is the one to have. You will have enough power to drive it. I have done 4.83 seconds 0-60mph on a completely standard renault box with 3.44 diff. 3.88 ratio diff will rush you through 1st and 2nd gears too quickly and likely buzz your engine to boot. However if you have the upgraded quaife 1st and 2nd shaft I personally beleive that the 3.88 diff is the one to have if you are going for quick lap times or hill climb times. This ratio will reduce the higher 1st and 2nd gear back to what the standard gears are but in effect reduce 3rd and 4th and 5th gears for better mid speed acceleration. Putting a tall 5th gear in for motorway cruising makes sense to me. I heard taller 5th gears cost about £150 but I am not sure of that. Again Chris Cole can supply that item.

Hope this is of help


[ July 09, 2002: Message edited by: Malcolm M ]

Howard Jones

Thank You all I can't tell you all how much I value this web-site. Bud in livermore Cal USA has always been close by and willing to help but reading all of your posts just makes me want to get out into the garage!!

Again Thank you all, Howard. San Ramon Cal USA