Gearbox approx power limit

[miked]

Hi Rohan,
I have been looking for an old post.
Do you recall us having a discusion quite a number of years ago about how robust the standard semi close box was. I appreciate this is dependant upon a quite a number of factors. I seem to recall you modified your opinion on this after subsequent findings on failures when racing.
The reason I ask is the possibilty of going back to a standard quiet box in the Zetec. Not going to track day or be dropping clutch. Odd spirited drive.
Cheers Mike

[rgh0]

In normal road use I think the box would be good for around 160 hp indefintely. A Zetec puts out more midrange torque but it will only make a little difference in life in road use I believe. In race use with the box at full load in second and third gears all the time I think it will fail at these levels due to fatigue. Mine failed after about 15 years of racing at these levels.

You can now get Quaife close ratio helical gear sets through TTR. The advertise them for race use only but they are as quiet as the orignal helical gears in my experieice. I am usng them now in my Elan. The also say you "must" use a specific 75W-140 oil. I find this to heavy and it ruins the gear change, maybe if you are doing 3 hour endurance racing you need it but my races are 20 minutes maximum. I use redline MT90 currently and may move back to the MTL I used to use in standardcbox or the Quaiffe straight cut gears as the gear change with the MT90 is not as good especially in the first couple of laps when the box is cold

cheers
Rohan

[2cams70]

No way will the Ford 4 speed bullet box stand up to the torque of a Zetec unless you drive like Nanna all the time. Torque is what kills gearboxes. Increasing the engine capacity from 1.6L standard engine to 2.0L Zetec will produce heaps more torque. A 1.6L highly tuned race engine does not necessarily produce a lot more torque than a standard engine so the standard gearbox can still cope. It will break behind a 70’s technology 2.0L Ford Pinto engine never mind a 90’s technology DOHC 16 valve 2.0L Zetec. Don’t forget that gearbox can trace it’s origin back to the 1959 0.997L Ford Anglia.

[rgh0]

No way will the Ford 4 speed bullet box stand up to the torque of a Zetec unless you drive like Nanna all the time. Torque is what kills gearboxes. Increasing the engine capacity from 1.6L standard engine to 2.0L Zetec will produce heaps more torque. A 1.6L highly tuned race engine does not necessarily produce a lot more torque than a standard engine so the standard gearbox can still cope. It will break behind a 70’s technology 2.0L Ford Pinto engine never mind a 90’s technology DOHC 16 valve 2.0L Zetec. Don’t forget that gearbox can trace it’s origin back to the 1959 0.997L Ford Anglia.

A developed 1600 twin cam will make around 130 ft lbs , a developed 1700 will make around 140 ft lbs. A standard 2.0 l Zetec will make around 140 to 145 ft lbs at around 5500 rpm and full throttle.

I agree if racing a standard boxes life would be limited behind a Zetec or a well developed twin cam but for road use even if not driving like a Nanna its not going to immediately fail. The key issue with a standard semi close box is that the gears are now 50+ years old and will have had a lot of their gear teeth fatigue life used up hence the comment I made about new helical gears now being available from Quaiffe via TTR.

cheers
Rohan

[2cams70]

A difference between a tuned race engine producing 140ft/lb and larger capacity road engine producing 140ft/lb is usually that the larger capacity road engine will produce more torque over a wider spread of operating speeds and stress the transmission more. Certainly the Escort modification boys (and girls to be politically correct) would never consider using the bullet box behind a 2.0L engine (Pinto or otherwise). Admittedly that crowd is mostly lunatics and not nannas. Ford themselves never used it beyond the 1.6L Kent and Pinto based engine series. The Lotus Elan (not necessarily the Plus 2) is a fair bit lighter which does help a bit. I'm always grateful for others to choose to be guinea pigs but it not something I'd consider doing myself.

[shynsy]

Yes. Guessing low end stump pulling grunt is the killer.
Tim

[promotor]

Hi Mike,

Hope you are well.

I recently did a 2000e gearbox for a guy with a supercharged crossflow - I think it was around 160/170 bhp (not sure on torque but it should be quite high being supercharged). I told him I thought he was daft but he insisted on going that route for now - and the car will be used on small rally events so is going to get some hammer. I keep asking for an update as I want to know what - if anything - causes its demise! He hadn't fitted at the last time of asking - if I find anything out I will let you know.
I did a semi close ratio gearbox for someone who owns an Elan with around 150bhp (twincam though, not Zetec) and that's lasted well - I've been in the car and it didn't struggle with gear changes under hard driving and is still in use.

[rgh0]

looks like TTR are now saying the helical close ratio gearset is suitable for road cars. They said this when they first started selling and subsequently changed it to race use only and now saying road use again?

https://www.tonythompsonracing.co.uk/pa ... -complete/

cheers
Rohan

[2cams70]

A bit of a story here. One thing manufacturers hate doing is developing new manual transmissions. They aren't sexy. They just do a job. If they could get away with using a 20 year old transmission design they would. A new Fandago Explosion twin turbo supercharged 50 valve engine will get the punters champing at the bit and salivating with hands scrambling for wallets. A new manual transmission won't.

If they don't have the budget or more typically the sales department wants to have the metal going out the door IMMEDIATELY, NOW because Desmond the Destructor motoring journalist is due to drive it at a product launch happening next year the engineers will work out a way to couple the new Fandango Explosion Engine to the 20 year old Rickety Bridge series transmission.

Sometimes they'll electronically limit engine torque in the lower gears because that's where things generally break. It may also be an option for you if you want to use a 2000E transmission and play it a bit safer. It is a sweet shifting gearbox.

[prezoom]

I have a close ratio gearbox in my Plus2 with a 3.55 diff. Have put thousands of miles on this combination with no problems. The engine is a 2L, with a custom bore expanding exhaust, the pipe diameters increase at specific distance to the end, and 45 Webers. But, otherwise standard other that removal of the variable valve timing on the exhaust cam. I do not due clutching dumping starts and hard shifts and love the combination.

[miked]

Thanks Rohan for giving me the information i asked for. Much appreciated. I will have a think on it. As you may have noticed I was considering selling it. Fatigue maybe with 2 house moves. Maybe ignite the flame and get back into it. Was going injection too.

Pity they did not do the helical gear set when I was splashing out on 3J drive line close ratio box and then changing to the MKF one to find it was as noisy. Fab ratios with the 3.55 diff. Sporty noise

Hi Al, yeah not bad thanks. Hope all is good with you. Need to have a Hassop station or Bakewell meet up with Paul and Co.
I did not intend to stir the pot with my question. I looked at TTR web site and noticed too that it says road use.

[2cams70]

In my experience from my misspent youth pulling many bullet boxes from the wreckers apart in search of the elusive semi close ratio gear set the main weakness I’ve found (apart from worn shift forks, synchro rings. etc. that aren’t due to the amount of torque being transmitted and clashing gears due to worn clutch or poor driving technique) are:

1. Wear of the countershaft and internal bearing surfaces of the countershaft gear.
2. Wear on the sides of the gear dog engagement teeth - particularly on the input gear.

On a normally driven relatively standard car broken teeth are very rare. Surprisingly significant wear of either the input or output shaft roller bearings is also very rare.

I’m not that familiar with the aftermarket gearsets available for these transmissions. Do they address the problem with the countershaft bearings?

The first you’ll notice if the gearbox is being used beyond its capacity is catastrophic failure of the gears without warning or increasing whine as the gears drop out of correct alignment due to countershaft bearing wear. The countershaft and its bearings are the real weak point. No change in design here since the 1959 Anglia

[promotor]

Thanks Rohan for giving me the information i asked for. Much appreciated. I will have a think on it. As you may have noticed I was considering selling it. Fatigue maybe with 2 house moves. Maybe ignite the flame and get back into it. Was going injection too.

Pity they did not do the helical gear set when I was splashing out on 3J drive line close ratio box and then changing to the MKF one to find it was as noisy. Fab ratios with the 3.55 diff. Sporty noise

Hi Al, yeah not bad thanks. Hope all is good with you. Need to have a Hassop station or Bakewell meet up with Paul and Co.
I did not intend to stir the pot with my question. I looked at TTR web site and noticed too that it says road use.

Glad to hear it Mike, all good this end thanks! A Hassop Hall meet would good, it'd be a good reason to test a new gearbox if you fit one.
I hope you get sorted with it soon.
Al

BTW - agree with you 2cams re the info above regarding the small needle rollers - and it's still an issue as no-one has solved it as far as I know, or perhaps not in an economical fashion that anyone would be willing to pay for.

[rgh0]

Hi Promotor

In my racing gear boxes with Qaiffe straight cut gears what has failed is the layshaft fit in the housing due to the shaft fretting and making the hole oval. The layshaft bearings and layshaft is still OK. I now make sure I have a very tight fit between the layshaft and the casing to minimise this risk. I suspect the straight cut gear vibration contributes to this which is why i am now trying the helical cut Quaiffe gears.

I have however pulled apart a number of old used gearboxes where the layshaft ground surface where the needle rollers run has started to fail.

cheers
Rohan

[promotor]

Hi Promotor

In my racing gear boxes with Qaiffe straight cut gears what has failed is the layshaft fit in the housing due to the shaft fretting and making the hole oval. The layshaft bearings and layshaft is still OK. I now make sure I have a very tight fit between the layshaft and the casing to minimise this risk. I suspect the straight cut gear vibration contributes to this which is why i am now trying the helical cut Quaiffe gears.

I have however pulled apart a number of old used gearboxes where the layshaft ground surface where the needle rollers run has started to fail.

cheers
Rohan

Hello Rohan,

When the needle rollers really get some grief they tend to get magnetized so that's always something to look out for (and it doesn't help things as it will attract metal particles into that area too). I've seen them so bad that they come out of the cluster gear like a string of sausages!

The loads on the needler roller bearings with straight cut gears is far worse than helical gear sets in terms of gear separation - at least the helical cluster gear shares the load (unequally) between the needle rollers and the copper or bronze thrust washers, depending on type fitted. Straight cut gears directly force each other apart so that all the load is all taken by the needle rollers.
I suspect road cars that are reversed a lot as a daily driver will have a little more wear in the cluster gear due to reverse gear train all being straight cut and the reverse ratio being quite low (although how much of a percentage a car spends its life in reverse it can't be the major contributor, but it's all part of the mix).

It's a tricky one as to how tight the layshaft should be in the case but as you say tighter is better within the original-as-planned figures. Anything with aftermarket parts may be looser or tighter - looser causing issues with fretting as you mention and tighter potentially splitting the case if it is extreme, although I've never seen them too tight on tolerance.

When I fit the reverse shaft and cluster layshaft I get them to fit so that the end profile is close to being wedged in the recesses in the tailcasing so that it has less chance of trying to spin under load as I think it only needs to have a couple of these events before it has moved and potentially loosened the case fit fractionally. Of course you can fit layshafts with an anti-spin peg, or machine the cases to accept your own modification for high loads seen in racing.

I've seen plenty of standard helical gear sets that have failed in the needle roller bore in the cluster - it's nearly always in 1st gear end due to 1st gear seeing the most torque compared to 4th gear end. I've seen only one that had failed in both ends - not sure what had gone off there other than it was just a very tired gearbox.

The problem is that I don't see many straight-cut gearboxes to be able to assess whether in service a helical gearset is better or worse and whether the gear separation loads between different gear forms cause issue. Perhaps materials are different between Ford and aftermarket which may impact things.

I did a gearbox with 2.5 Quaife TTR semi-helical gearset recently and the teeth are strong looking. This one had been "superfinished" but I'm not sure if that's better or not as there doesn't seem to be any place for the oil to stick due to how smooth the finish is. No feedback on the gearbox as it's not been run yet.
I like free things but I wasn't happy about the ceramic tile used in the superfinishing process being wedged in there! It needed some persuasion to get it out!