DRAFT: Fiat Gearbox Swap
There are numerous Fiat boxes that with varying ease can be adapted to fit. However the later stronger ones often need cutting of the Niva body to fit. Here’s some notes I’ve collected from others:
Firstly:There are numerous gearboxes that will fit from the Lada cars, with as many different ratios. If I remember rightly the one to get is from the 1500cc 4 speed estate which has a low ratio 1st gear and is somehow stronger. The Twin cam never broke it anyway.
5-speed vs 4-speed Lada ‘boxes
Anyway:
All of the 124 series Fiat boxes will fit.
Fiat clutch sizes vary by model, but the input splines are identical, so there is no need to change the clutch palte over. Please note that the Fiat overdrives are much lower than the stock Lada ones(Fiat gears =0.88:1, 0.912:1, 0.913:1, Lada overdrive =0.82:1), so your revs will increase when in overdrive. This works great if you are using oversize tires, but could be a problem with stock rubber.
Sedan versions will bolt up as follows. Remove the Fiat bell housingfrom the main gearbox, then fit up the Lada bell housing, and releasebearing(this is because Fiats never came with hydraulic clutches.). All the internal passages, and bolt holes in the rear of the bell housings are identical, so there’s no problem with the fit. Two different styles of overdrive unit were used on the Fiat's, the early ones will bolt directly up to the Lada transmission cross member. Later models require that you use the bracket that fits onto the Fiat tranny. You remove the original Lada flex coupling from the cross member, then cut a groove into the cross member, drill 4 holes (using the Fiat part as the template) and bolt up the Fiat bushing/bracket assembly.
Fiat 124 Spider transmissions will also bolt up to the Lada bell housing, but do require some cutting of the floor pan as they use an extended shifter assembly. As far as I know all Spiders use the later style trannies, with the Porsche style overdrive, so they will require the same cross member modifications detailed above. On the plus side the Spider shifter sits about 7 inches farther back than stock, which is where the shifter should be in the first place, and the Spider trannies come with a slightly lower first gear (3.8:1).
FYI I'm using a 1973 1800cc Spider transmission, with the 0.912 overdrive, and the 3.8:1 first gear. I acquired the pistol grip style shifter from a 1979 Fiat station wagon, which has exactly the right length to leave it 'in hand' when fitted to a Niva. The transmission is much smoother running, and generates noticeably less driveline drag. The gears are spaced for 'spirited',' Italian style driving, and acceleration has actually improved because of this. The lower overdrive really only means fewer downshifts on hills, and has made about 1/2 MPG improvement in my highway fuel economy.
THINGS TO WATCH FOR - like the Lada copy, the weakness in the Fiat box is in the shift forks. They are surfaced with some sort of soft bronze alloy, and are prone to wear if the driver has done long trips, leaning on the shifter. Easy fixes include re-brazing, and re-finishing them, or potentially a pottery shop could build you some ceramic inserts for the shifters. Several speed shops in the USA still carry spares for Fiats, but I won't vouch for availability elsewhere in the world.
These ‘boxes are apparently 90mm longer than a Lada ‘box – so how does this marry to the transfer case?
The shifter on mine comes through in the exactly the same spot.
Just make sure you get a 124 gearbox with the shifter as in the nivas (ie: floor shift not column shift!) AND with a sump plate like the nivas.
Hi I have a Niva fitted with a fiat 124 4speed. The fiat gearbox boltsdirectly onto the original Lada bellhousing. The revs are slightly lower thanthe original 5speed box.
Here are the approx. revs at diff speeds
3rd gear
60km/h 3000
70km/h 3500
80km/h 3900
90km/h 4400
100km/h 4900
4th gear
60km/h 2250
70km/h 2600
80km/h 2950
90km/h 3300
100km/h 3700
110km/h 4050
120km/h 4400
130km/h 4800
140km/h 5200
I only briefly took the car to 140km/h
I travel max around 110km/h
Consumption for combined urban and open road driving averaged at around 11 l/100km
The fiat 124 4speed is incredible for offroading and mountain driving.
The ratios are different to the original boxIt gives a lot more power in 1st and 2nd gearsCompression in 1st is incredible and excellent for steep descents
I am very happy with the fiat 124 gearbox
Regards,
Michael
Latter ones may need body alterations to fit (eg FIAT 131, 132, Argenta "long-neck") the early type of Fiat131-gearbox, makes much less problems, ie the shift stick will be at the Lada shift stick's place, and the starter is at a better position (though using the Lada bell-housing might sort the starter and cable-to-fluid clutch problems).
The gearbox. (this is about the later ‘longneck’ ‘box)This type FIAT gearbox is well known. It differs from the Lada gearbox. It has a different shape. Body is 90mm longer. It has 5 speeds and a more comfortable shift stick placement. It is bolt-on to the engine. This means that it can be fit on a Lada engine, but the clutch housing size is different, because of the 2.0 litres Fiat engine has a larger flywheel. The starter is on the left instead of the right.
The 131/132 ZF style ‘box: