Longer gears or 6 speed gearbox for 1.9TD (XUD9TE)

[Deacon]

Alright then, I am gonna have a chat with my technician. See what he thinks about the HDi BE3 on a 1.9TD, or better, see if we can source a BE3/6 from a 306, swap the gears as standard on a 1.9TD BE3 and just add some overdrive, longer gear for 6th whenever the road conditions permit for its use.

[EDC5]

I wonder what the RPMs, acceleration, and speed would be on a 1.9TD with a 90 hp HDI gearbox. If anyone has tried that?

I know that the HDi boxes had a bit of longer gearing but by how much when compared to stock 1.9TD BE3?
Checked the prices, this looks like a dirt cheap alternative!

I suspect it would be fine as both engines were 90hp units. I'm guessing the main reason they lengthened the gear was for fuel efficiency which was less important in the XUD days?

[citroenxm]

No. Lengthen not just for economy but because the hdi torque is higher and lower down the rev range over the xudtd. No point revving to high over your peak torque window

[white exec]

If you could just swap the 5th gear cog-pair, that would be an interesting option. I haven't worked on a BE3 box, but have renewed Toyota 5th gear clusters, which lurk under the end cover, and are easily accessible (and removable with a suitable puller).

[MikeT]

Fit the HDI box and tune the XUD9TE to match.

[Zelandeth]

Don't think the Activa *needs* an extra gear. 70mph is a fraction over 3000rpm it looks like. Just sounds like she is revving quite high compared to a lot of modern cars. The fact that you can hear the engine is mainly a function of how quiet the rest of the car is by the standards of the time.

Was more a "wish list" idea for me really as it felt like the car could handle it.

Easy to forget how different things were a few years before - Lada is pulling nearly 4000rpm and the exhaust is howling at 70mph...

[Michel]

Don't think the Activa *needs* an extra gear. 70mph is a fraction over 3000rpm it looks like. Just sounds like she is revving quite high compared to a lot of modern cars. The fact that you can hear the engine is mainly a function of how quiet the rest of the car is by the standards of the time.

Was more a "wish list" idea for me really as it felt like the car could handle it.

Easy to forget how different things were a few years before - Lada is pulling nearly 4000rpm and the exhaust is howling at 70mph...

It was the one thing that bugged me about my Activa, very busy on a long journey - exactly the sort of thing the rest of the car was suited to, but they had to spoil it with the boat-anchor TCT which is neither powerful or economical in standard form.. just gruff and thirsty!

[Deacon]

Had a talk with my mechanic. He has a spare 306 GTi 6 speed BE3 gearbox. In the past, he tried this with a 1.9 TD BX. They managed to reduce the RPM in 6th (with BE3/6) to 2700 RPM (instead of 3000 RPM on stock BE3, later got the same result with "tuned" 5 speed BE3) while moving with 130 km/h. Once, after loads of gear and gear shaft drilling (not just simple gear swap), they managed to put an even longer 5th gear to further reduce the RPMs from 2700 to 2500 RPM, which left the engine struggling when going uphill or sudden acceleration was needed. The saving of fuel was marginal. He said that unless I was 100% sure that I will do long journeys on even roads, the experiment wasn't worth it and better deal with a bit more fuel consumption. For me, that was the main reason to try this, the engine high rev sound isn't that big of an issue.

I found the gear ratios to all BE3 gearboxes and secretly did the calculations, there are online gear ratio calculators. Going with what's available for simple swap and no drilling, you could bring the RPM down only to about 2700 RPM when doing 130 km/h.

I guess back in the day they didn't care about fuel economy, emissions and engine wear (considering the enormous compressions that older diesel run on), so no 6th gear lol. Check out Euro 1 and 2 standards, they don't even care about NOx emissions...

TL;DR: Yes it's possible to fit longer gears to a BE3 gearbox on a 1.9TD or fit 6 speed BE3 gearbox from a 306 GTI with changed gears (that will require some drilling to the housing and shaftways), but that would be more for your own comfort if you find a long, even stretch of a road. The fuel economy won't be that much affected as you'll need to almost floor it if you meet a hill if you remain in the highest gear.