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R4 5 speed gearbox

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134
#1
I've been reading about fitting a 5 speed gearbox from a R5 to an R4 on the forum.
Does it fit like for like or do you have to get a big hammer out! Does it use the same dash mounted gear lever or do you have to fit a floor mounted one.
Also, I think the 4GTL may have a higher diff ratio so will I get any benefit from the 5 speed on the motorway or will there not be much difference?
 

malcolm

& Clementine the Cat
Staff member
Messages
4,215
Location
Bedford UK
#2
I'm in the garage going through Haynes manuals. Turns out the 5 speed gearbox I hope to fit to my car has a lower top gear than the standard GTL gearbox:

Renault 4 GTL
4th gear ratio: 1.026:1
Final drive 3.1:1
4th * final drive (total ratio) 3.18:1

Renault 5 TX
5th Gear ratio: 0.95:1
Final drive 3.44:1
5th * final drive 3.27:1

Looks like the 5 speed thing is about closer ratios rather than long legged cruising.

The 5 speed box is slightly longer so you would need some modifications to the front crossmember. The brolley gearlever can still be used if you fit the gearbox top cover from the 4. I'd guess the R5 clutch is the one to use.

Enrique posted some photos of his rather substantial crossmember modification on http://www.renault4.co.uk/forum/about164.html

:clementi:
 

malcolm

& Clementine the Cat
Staff member
Messages
4,215
Location
Bedford UK
#3
I think I've found the answer:

A standard Renault 4 GTL with 135/80/13 tyres would be doing 60.3mph at 3000rpm. If you fitted 145/80/13 tyres you could up that to 62.1mph.

If you fitted the 5 speed gearbox together with 145 tyres then you'd be doing 60.4mph at 3000rpm, so the gearing would be slightly higher than the standard car, and you'd have that extra gear to play with.

135 and 145 tyres were both recommended for the R4, and the speedo is more accurate with 145 tyres, so you'll be able to go faster!

Mike: I like your blue R4 in the gallery by the way. Did that come off eBay - it looks familiar.

:clementi:
 

Chris H

Enthusiast
Messages
72
#4
60mph @ 3krpm in top is about the same as on the 19 range, well the 16V is about 64mph in 5th at 3krpm.

That gearing is well suited to the cars power band.

if you start upping the gearing a lot fuel economy will suffer.
 
Messages
134
#5
Clementine (Malcolm?) yes the car came off ebay for a tenner! Just done 250 miles at the weekend without a hitch. I'm now thinking that I'll get rid of my Rangerover in favour of the R4!

The fuel consumption didn't appear to be as good as expected; the exhaust looks a bit sooty! There is a screw on the side of the carb which I think is the mixture screw, do I screw this in or out to lean the mixture?

How does the 135 to 145 help with the gearing by the way? I thought those figures represented the width of the tyres as opposed to the depth.

I actually found the gearing to be fairly laid back, cruising at 60-65. What do you think the limit is for cruising; would 70 be asking a bit too much? I felt that it would be ok although it couldn't have been far from the maximum speed!
 

Chris H

Enthusiast
Messages
72
#6
mixture screw only affect idle mixture and up to the progresion slots are no longer used about 2krpm. In to weaken it.

135 to 145 will help as 135/145 is indeed the width of the tyre they both use the same sidewall ratio of 80. So a 145 tyre will have a bigger sidewall thus an overall increased tyre diameter.

If it will get to 70 and stay there without your foot flat to the floor and the temp doesn't go to high then I'd say thats fine.
 
Messages
134
#7
Thanks Chris, I thought the numbers were measurements not ratios as you point out. You learn something new every day!! Mine already has 145's fitted which would explain the relaxed cruise!
I don't have a temperature guage fitted but am thinking of fitting one.
So, how do you lean the mixture out over 2 krpm? Do you reduce the size of the mainjet?
Also, when I'm due for new tyres, would I be pushing it if I fitted 155's?
 

Kamikaza

New Member
Messages
4
#8
HAHAH

I FITED 165/80/14 ?? BIT OF CUTING OF CHASI AND IHAD MAX 150KM/H MESURD BY POLICE RADAR ????wow FILING LIKE YOUR GING 250KM/H :cool:
 

Chris H

Enthusiast
Messages
72
#9
fit a different emulsion jet, less holes means richer mix and vise versa

or fit different air correction jets.

I much prefer EFI, you can adjust the trim as you like, none of this hit and miss crap with carbs! :wink:
 

angel

Enthusiast
Messages
2,031
Location
Athens, Greece
#10
Hi Mike. You don't have to take a hammer to fit the gearbox. Just an oxyacetylene torch and a MIG welder to cut and reposition the front crossmember since the 5-speed gearbox is a bit longer, otherwise the conversion is straightforward. The R4 top cover will fit on the R5 gearbox casing without modifications so you can still have the R4 lever (the way most people prefer). I did such a conversion recently but I fitted the R5 1108cc engine as well. As the engine is being run-in, I haven't had the opportunity to measure top speed yet.
 
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