Un-1 DB upgrade vs.ZF/Porsche G50

So here is my next quis...

Is it some on this forum that have knowlege about the Derek Bell UN-1 upgrade? I have used a stock UN-1 in my Esprit with 400ft/lbs,and He claims the upradet version is 40% stronger than stock.

I did read on this forum that the casing is the next week point so the box will flex.

Is it someone with hige torque engine on a DB UN1 upgradet box?

Is the Derek Bell UN-1 upgrade as strong as the ZF/ porsche G50 5 speed?

Perhaps this?
http://www.gt40s.com/forum/showthread.php?t=18082

Ian

Thats a 6speed straight cut...May be my next quis..
I`m talking about the 5 speed...

Yes this is 6 speed BUT it fits in the UN1 case and is supposedly good for big powere stuff.

I believe they managed 6 gears by
1) Moving reverse out of the box to the overhang section where 5th normall sits
2) this frees up space inside the case allowing the extra 2 to be fitted internally allowing shafts that have bearings at both ends

But straight cut could be very noisy for the road

Ian

IanAnderson said:

Yes this is 6 speed BUT it fits in the UN1 case and is supposedly good for big powere stuff.

I believe they managed 6 gears by
1) Moving reverse out of the box to the overhang section where 5th normall sits
2) this frees up space inside the case allowing the extra 2 to be fitted internally allowing shafts that have bearings at both ends

But straight cut could be very noisy for the road

Ian

Click to expand...

And a high revving small block with crossovers isn't ??

Ian K

I have a UN1 gearbox on a 406 cubic inch, all alloy V8. It produces 550 horsepower and 535ft/lb torque at the flywheel.
I looked at the Bell upgrade and thought it a good idea. But I did find it very expensive. So I made my own based on what was done there, plus a few other things. My gearbox hasnt blown up. BUT I dont do drag racing, hillclimbs or rally sprints. It has seen a few days use at racetracks though and can well foot it with Porsches and other such racewagons. It does have the capacity to peel the rear tyres in 3rd if you plant it hard, otherwise driving with sympathy for mechanical things goes along way to keeping it alive. Dont get me wrong, it is not treated with kid gloves and has dusted off its fair share of rice-cutters. Just have to remember, dont smoke the bags or dump the clutch.

Well I`m also driving with care....

But is there any on this forum that knows how strong the Derek Bell upgradet
UN1 is??
What is gona be the next problem? casing,pinion,etc...

I did read that the 6speed is 2 times as strong as the stock UN1.
Then the 5 speed DB upgade should be pretty close???

I like the idea of the 6-speed box. But remember all you will be doing with that is changing gear more often. Looking at the photos of the 6-speed, I dont know how it can be stronger, even double the strength of the 5-speed. Why? Well for starters the gear teeth look somewhat small and straight cut are not as strong as helical for the same given size. Perhaps the theory of input shaft flex of the standard box has been addressed with the 6-speed, certainly has with the Bell upgrade where shaft size has gone up from 19 to 27mm on the 5th gear end. (undercut).

Have a looky at the picture a bit closer. Whats that large aluminium plate for? Looks to me like a strengthening plate for the rear thrust bearings, moreso for the output shaft where there is incredible forces pushing the shaft back against the bearing thrust plate. This force is of course offset with helical gears to an extent.

As for case flex ...... as much as it probably happens on high torque situations, I think its more of an issue coming from too much pub talk. Most flex will be in the lower gears and 5th where there is the greatest distance from the crownwheel/pinion contact to the 5th or 1st gear. Least 'flex' would occur in 4th gear. You certainly wont be able to measure this 'flex' with a ruler, nor see it happening. But to be open to comment, how many of you Renault box users have experiences 'case flex'?????

As for the pinion, well again, you abuse it, it will break. I sold a Renault 20 5-speed to a guy who has an off roader. He is on his 3rd crownwheel and pinion set. Why? Because when they go over jumps, they have their foot down and when in the air, the wheels are 'free-wheeling'. Come back on the ground and its instant power on through the box. Hence something tends to fail. Similar to revving the engine to max torque level, car with slicks, and then taking your foot off the clutch sideways - eg, instant take-up. I bet I could destroy a ZF or Porsche box the same way. If anything in there is going to break it would probably be the differential unit. Upgrade or change to a Quaife unit.

There are always going to be figures of strength tossed about in talk. To get a realistic idea - look at all those who have Renault boxs in their GT40s. Have a peek at the videos in 'other' site at guys hillclimbing and sprinting and they have no trouble with their boxes.
Sure, the Renualt box isnt going to all out as strong when you put Porsche, ZF and Renault side by side, open on a workbench.
If you do have concerns about its strength, then save your money and buy a Porsche.

I have 2 UN1`s here. One in the Lotus and 1 spare...
You have right about the 6 speed...You gona change gear all the time...
I gona build a engine with a wide power range.So I dont need a close ratio.

The Derec bell upgrade is £2000,- from UK
What do I have to pay for a ZF? and where do I get them used?

The Porsche is gona be more difficult to fit...Need to cut the frame and weld it.

I have the DB upgrade in my car and I have done many standing starts with it. My engine produces somewhere in the region of 360 to 400 bhp and same numbers for torque. Not dyno tested or bothered to test but car goes quite well! Prior to upgrade I bust the input shaft at the spline something the DB upgrade sorts out well.

Since upgrade never had a problem. And I have used slicks for these starts and also dumped the clutch at 5000 rpm for a 2nd gear pull away. DB upgrade seems to take the abuse. My car has 13 years of competitive use on it.

Others have much more BHP than me and use the DB upgrade too. I am including Roy Smart and Dave Parker with the highest power output engines (ie in excess of 500 bhp) and I am not aware of them having issues.

What busts next is not the casing. The only way I know of to bust a casing is to not build the box properly and not pin 5th gear. It unspins itself and punches a neat hole in the rear casing. Tell a lie, you can also bust the casing if the 1/2 inch pins in the diff come out and it jams up solid when you are doing 60 mph. Breaks the whole casing in half and is un-repairable!

But the casing does not flex! I have known of no casing failures through a fatigue situation.

What breaks next? You have a choice. The friction plate in the clutch can fail. The springs pop out!

You can have drive shafts snaping but not that common. Or the CV joints shatter.

IMHO the causes for these are 1. to many standing starts without replacing the friction plate regularly and 2, playing around with suspension positions so that the drive shaft is not fully connected in the CV and finally 3. to much grunt or not replaced early enough. Most go for a CV failure as a simple and quick track side repair. You got to have a weak point somewhere!

The majority of these failures come from a lot of track and competition work not road use. Most road tyres do not have the grip to stress these components enough.

As to as strong as a ZF and G50? No one has done back to back tests that I know of. The ZF really comes out of a lorry and so has good chunky gears. Ratios are quite tall if you want lots of standing starts. A strong box in my view.

G50 is well proven on track and has lots of upgrade options.

Cheapest of these three is the DB UN1with G50 close second, unless you go for upgrades and ZF highest cost. You got to allow for modding your car to take a different box whereas with the DB upgrade it is just the friction plate (spline is different) and you need to ensure your clutch line is 1/4 inch and change master cylinder to 1". No one knows why this last mod is needed but everyone has done it! Bite point is beyond the front bulkhead unless you change the master cylinder. Clutch is quite heavy as a result which sucks for road driving.

A new option coming onto the market is the GTO engineering 6 speed quaife upgrade that is as strong as the DB upgrade but also has a better gearbox weight than before. BUt it costs more than DB upgrade so if cost is an issue this won't be for you.

Finally and please don't take this the wrong way, if you build an engine over 400 bhp you are asking for gearbox concerns. Build the engine you suffer the consequences. Domino effect.

Hope this helps.

Thanks a lot..
Do you think the DB upgrade is as stong as the 6speed from GTO?
GTO rate that it will take 2 times the load what the stock UN1 can take.
And I have used my on a lot of track use with 400bhp/375ft/lbs...
Then it should take my next prosject with 700bhp/600ft/lbs......

Well this isnt easy.I wish some one could donate a gearset and then they
will know next year if it can take it...

DB / Quaife UN1 Upgrade

Hi Rydning, welcome to the forum..

Re power capacity of DB converted box, who knows? - Derek would not want to quote a specific rating as for sure, someone would then break one and point the finger.

However, to my knowledge, no-one has broken the gear train or shafts in a DB/Quaife converted UN1 to date - period!

Derek himself has a well tuned small block Chevy powered GTD Lola T70 that has seen quite a lot of track time.

Dave Parker has a GTD R42, again Chevy powered and now stroked to 6.3L. Running Motec Fuel injection, 8 coil ignition it is putting out in excess of 500BHP for sure! and has numerous hill climbs/sprints under it's belt. The Box must have survived at least 200+ standing starts, many with a tyre warming session beforehand and Dave runs W-I-D-E Hoosier slicks - (hell it's survived about 40+ from me!) and as we are nicknamed 'leadfoot' and 'hooligan' respectively its probably a fair test. Dave's R42 weighs about 1350Kg so work the maths, the box has not had an easy life for sure. A 150BHP shot of NOS later this year should test it further still.

Personally, I would rate the std GTD/UN1 for up to about 380-420BHP or possibly a bit more providing you drive it thoughtfully!! Burnouts, standing starts and lots of wheelspin will break it in short time regardless......

Having said that, Rodger Burston still runs a std UN1 (but with Quaife ATB Diff) in his GTD which now runs a stroker 351 (408ci) with AFR heads and 48IDA Webers - explain that one! And don't suggest 'he aint trying hard enough!' - This video from Shelsley Walsh Hill Climb a week ago shows otherwise http://www.gtd40club.co.uk/videos/GTDs%20at%20Shelsley%20Hill%20Climb%202006.wmv

Thanks this forum is one of few that I have got usefull info on.

Is it possible to do fast gear changes with the DB upgrade?
I realy have to make slow gearchanges with my stock UN1...

And I did go thru the ratios.And i realy liked the 6sp from Gto and it looks to be very strong.Its gona be perfect for the track,and to do fast gearchanges in some street legal dragracing (1/8 miles).But noisy...

The thing is I have never seen this uprades, and thats why I have to obtain as mutch info as possible before I order...
Do you think it will be stronger than the DB uprade?
It looks like you have seen both conversions?

rydning said:

Is it possible to do fast gear changes with the DB upgrade?

Click to expand...

We have data logging on Roy's Mk1 which has had a strandard UN1 with cable shift, the DB Conversion and finally DB Conversion with Rod Change.

The fastest shifts recorded If I recall were about 0.3s, on standard UN1 with cables. These were straight shifts (1-2, 3-4) cross gate shifts took on average 0.5s to 0.6s (2-3,4-5).

The DB conversion did not change this but did shift the change point due to the longer 1st and 2nd ratios, which gave faster speeds in both gears.

Moving to a Rod Change initially slowed the change for both Roy and I but once we got used to 'its feel', we were as fast as before. In my opinion a perfectly set cable change will shift as fast and reliably as a well designed rod change. The rod change does not generally suffer from the 'vagueness' that can develop with the cable change as joints wear etc. Once the cable ends wear, or if anything comes loose, missed shifts will prevail...

Ahhhhh so you want to go drag racing. Well I think you best forget you ever heard about manual transaxles and get an Automatic.
Get the tranny out of a Corvette, an auto one, and you'll be fine.
Just have to jigger the mountings because the diff in the 'vette is at the 'back' of the gearbox.

This is not real dragracing....Its on normal road surface and of couse I use the head when I do this....Most of the driving is on the track anyway.