Lotus Elan

4 Speed Gearbox rebuild

PostPost by: Craven » Mon Nov 02, 2020 2:32 pm

Workshop Manual gives. 1st gear 0.127 – 0.254mm end float. Same for 2nd gear. 0.127 – 0.406 for 3rd gear. Mainshaft end float 0.76mm Max.
Would seem the supplied spacer may be a bit too thick.
Re increase in rear bearing oil supply, extra oil pickup is made by groove arrangement in a modified spacer/trust pad behind 1st gear and an appropriate groove in the rear bearing carrier.
Can’t find a spacer but this is the carrier, this mod is part of the reason you have various circlip grooves which will match early draw nut parts with the later snap ring mainshaft.
P1030594.JPG and
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PostPost by: rgh0 » Tue Nov 03, 2020 1:23 am

Craven wrote:Workshop Manual gives. 1st gear 0.127 – 0.254mm end float. Same for 2nd gear. 0.127 – 0.406 for 3rd gear. Mainshaft end float 0.76mm Max.
Would seem the supplied spacer may be a bit too thick.
Re increase in rear bearing oil supply, extra oil pickup is made by groove arrangement in a modified spacer/trust pad behind 1st gear and an appropriate groove in the rear bearing carrier.
Can’t find a spacer but this is the carrier, this mod is part of the reason you have various circlip grooves which will match early draw nut parts with the later snap ring mainshaft.
P1030594.JPG


Interesting information

That later bearing carrier for the snap ring main shaft was thicker and the bearing slightly repositioned because of that. The Quaife main shaft uses the snap ring but its designed to use the early bearing carrier and bearing location. The Quaife instructions provide details of how to modify the later carrier to locate the bearing in the right location for the Quaife main shaft. It looks to me like the groove was added because of the thicker bearing carrier shielding the bearing more from the lubricant and this was added to aid that. probably unnecessary on the earlier carrier ?

The smaller end float on first gear than original is not a great concern to me. The gears all run on needle rollers. The end float I believe is required mainly to allow oil flow to the plain steel on steel original gears and main shaft ( with a bush for first gear on the draw nut early shafts). The needle rollers will require much less oil flow so the lower end float is probably adequate. Also not easily adjustable without surface grinding the spacer washer so I think I will go with the design per Quaife and not attempt to adjust it. Do you know if people using Quaife boxes have reported issues with the lower end float on first gear ?

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PostPost by: Craven » Tue Nov 03, 2020 1:02 pm

Your theorising on the oil feed modification to the rear bearing is completely wrong, in fact the space between the 1st gear and the bearing has been increased by a thicker spacer with oil collection groove. Combination of splash oil from the groove in the carrier channels oil to the rear bearing, extra oil passing through the bearing is returned to the main gearbox case by an extra return hole in the tail case.
Thicker bearing carrier is needed to accommodate the effective position rearward of the bearing caused by the thicker spacer between 1st gear and the bearing, the recess in the tail case is deeper to accept the thicker bearing carrier.
Spacer provided that fits between the bearing and circlip compensates for the difference in thickness of the inner spacer.
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PostPost by: rgh0 » Tue Nov 03, 2020 8:43 pm

Yes I may be wrong.... been that many times before :D

However the main shaft bearing will get all the lubrication it needs from the oil mist in the gear box I believe. The thicker spacer with oil grooves for use with the later main shaft bearing carrier appears to have been deleted by Quaife and replaced with a machining and spacer fitting operation on the later bearing carrier to relocate the bearing to the same position so it uses the same thinner plain spacer between bearing and first gear as the early bearing carrier.

Whether oil grooves are needed on this supplied thinner plain spacer is another question but there are grooves on the Quaife gears themselves and with needle rollers there should be plenty of lubrication IMHO.

The fundamental question remains however in that has there been reported issues of problems with the main shaft bearing or first gear needle roller bearing with the standard Quaife assembly using the early bearing carrier as I am doing? I have raced with my current Quaife box with the early bearing carrier for 30 years with just one rebuild about 15 years ago due to wear on the layshaft mounting holes due to fretting which is why I am building another box now- just in case as i had the engine out and no racing due to Covid. My experience says there is no issue but always interested in other actual experience as I hear tales of UK racers rebuilding gear boxes every year but I have never heard why this is required?

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PostPost by: Craven » Tue Nov 03, 2020 11:19 pm

I have no personal knowledge of Quaife modification but understand the gearset was withdrawn from production. My own C/R box uses the MKF gear set but the mainshaft has the nut retention, no jumping out of snap ring.
You seem happy with the inclusion of gears running on needle roller bearing along with additional spiral oil grooves on the gears yet reject the later improved rear main bearing modification thought necessary by Ford as unnecessary.
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PostPost by: rgh0 » Wed Nov 04, 2020 12:11 am

Craven wrote:I have no personal knowledge of Quaife modification but understand the gearset was withdrawn from production. My own C/R box uses the MKF gear set but the mainshaft has the nut retention, no jumping out of snap ring.
You seem happy with the inclusion of gears running on needle roller bearing along with additional spiral oil grooves on the gears yet reject the later improved rear main bearing modification thought necessary by Ford as unnecessary.


Interesting discussion on the details of gearbox modification. One of the reasons I like challenging myself with racing is understanding the limits of the various components that are pushed in competition and how to achieve reliability.

The helical tooth gear set was based on the same design as the straight cut race gear set and first introduced as a road / race gear set. The initial production proved too noisy as as a road gear set and production suspended while the issues were investigated. The sets are being sold now as "race only" by TTR who are the sole agents. I am told by TTR that the issue was due to deburring / surface finishing of the helical gear set. The set I got was from the corrected manufacturing and nicely polished. I am using it for racing so the noise issue is not a concern but it will be interesting to compare it to my current straight cut Quaife gear set and the original Ford helical gear set in terms of noise levels. My hope is that it is quieter than the straight cut set and good enough for limited road use but time will tell ( I still have my Elan road registered !)

Ford made multiple changes to the later snap ring gear box including deleting the sleeve that the 1st gear used to run on. My belief ( just my opinion ) is that this total set of changes started with the snap ring design adoption and 1st gear sleeve deletion and this drove the other changes made to the bearing and first gear spacer and lubrication arrangements. There appears no history of the standard draw nut boxes with the first gear sleeve needing these changes.

Yes while Ford found these mods necessary for their overall snap ring design the Quaife snap ring design is more similar to the original draw nut design in lubrication terms. I know enough about gear boxes and gear box design and lubrication to know that Quaife know more than me in terms of gear set and lubrication design so I will stick with their design for their gear set unless evidence emerges of a basic design flaw which I personally have not seen in my usage experience and similarly others I know racing Quaife gear sets here in Australia. The MKF design may require, and they may recommend, different arrangements, but I don't have direct experience and cant comment. Maybe others with experience using the MKF versus Quaife gear sets can comment ?

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PostPost by: baileyman » Wed Nov 04, 2020 2:58 pm

I have I think the last such set sold by TTR before the noise issue reared up. For the first few hundred it made a bit of noise but now after a thousand it is unobtrusive, similar to my S2000's box. John
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PostPost by: rgh0 » Sun Nov 08, 2020 6:17 am

continuing with the rebuild.....

Just a note that the TTR supplied snap rings are not very good as the ends have not been properly angled to be gripped by flat bladed snap ring pliers. I decided to reuse the old ones and I guess I can file the correct angle if I need to use them.

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Fitted the bearing on the input shaft and fitted the snap ring

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Cleaned up the gearbox casing components. Whoever worked on this box before I bought it loved using silicon sealant. You would not want these blobs of silicone blocking any of the gear lube holes. The rear seal had been plastered with some form of sealant inside and out ...was this an attempt to stop it leaking ? The drain hole back from the seal under the bearing also blocked with sealant.

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Pressed out the bearing with a suitable sized socket. I will make a machined drift to properly fit the bearing to avoid damaging the end when I refit the new one

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Removing the reverse gear shaft by pulling with a bolt and socket

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Casings are all apart and cleaned. Now to do the Quaife mods to the reverse gear and shaft so that the Quaife gears don't hit them.

...to be continued
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PostPost by: rgh0 » Sun Nov 08, 2020 6:34 am

To fit the TTR gear set the end of the reverse idle gear shaft needs to be machined down and the hub on the idle gear also machined down. On some of the later gear boxes the boss that the shaft fits into may also need some grinding but that was not needed on my early case

IMG_9315.jpg and


shaft in the lathe for machining

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had to change to the 4 jaw chuck for the gear as due to the gear teeth position it would not centre correctly on the three jaws. Setting up with a dial gauge to get the gear centred

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Completed modifications

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Gearbox is now ready for assembly of shafts into the casing ... to be be continued

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PostPost by: rgh0 » Sun Nov 15, 2020 6:40 am

Not much progress this weekend as other stuff to do, plus took my Esprit for a drive with the lockdown in Melbourne ended.

Found time to make up a tool to press the gearbox tail bearing in and out so I can get the new bearing in without damage. 33.0 mm larger diameter fits through the tail bearing mount bore to drive bearing out, 30.0 mm smaller diameter fits inside the bearing to centralise the tool

IMG_9390.jpg and


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PostPost by: rgh0 » Mon Nov 23, 2020 9:49 am

Continued with the assembly of components into the box.

Strings in position to lift layshaft gear cluster into final position once rest of shafts in place and thrust washers stuck with a little assembly grease into position. The manual says fit the reverse gear later but I find it easiest fitting now before placing the cluster gear in the base of the box so you are not fitting it with the layshaft gear lying loose in the bottom of the box.

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Layshaft gear and dummy shaft and needle bearings and washers and after assembly

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Layshaft in base of the centre casing, need to be careful not to loose washers out of layshaft or displace the thrust washers in the casing as you drop it into position after passing in through the rear of the casing. You can see how tight the clearances with the Quaife gear set first and second gears on the cluster gear with the reverse gear shaft and collar for the reverse shift fork and why they need to be machined down

IMG_9439 - Copy (3).jpg and


Now input shaft assembly can be fitted through to front of casing from rear. Snap ring located in bearing groove and front seal carrier bolted into place to locate bearing. Paper gasket and my preferred Loctite aviation Gasket cement and sealing of bolts threads with thread locker to prevent leaks through this front seal carrier. Manual says protect the seal by taping the splines as you fit the seal carrier as its diameter is smaller than the splines but this only applies to the earlier gear boxes that has the smaller diameter seal, the Quaife gear set and seal carrier have the later larger seal.

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Rear gasket in position stuck on the rear face. Make sure the reverse gear shaft alignment key is located to fit in the slot in the rear extension housing and the same with the lay shaft when that is fitted

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Gearbox output shaft cluster fitted, remember to fit the bearing and top gear synchro onto the input shaft before fitting the output shaft assembly into place. Also the layshaft lifted up and dummy shaft tapped out with longer layshaft. Ensure the thrust washers have not moved and the gear is lifted to align the shaft with the casing holes so the dummy shaft can be tapped out.

IMG_9447.jpg and



All the shafts now in position... to be continued

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PostPost by: rgh0 » Mon Nov 23, 2020 10:10 am

Now starting on rear extension. Pressing new bearing for tailshaft into position using the press tool I made previously

IMG_9448.jpg and


Rear extension bolted into place with aviation gasket cement on the paper gasket and thread locker on the bolts to prevent leaks at this join.

IMG_9449.jpg and


Rear seal fitted into position. I use a thin smear of Loctite 518 sealant on the seal metal outer casing to ensure no leaks past the outside of the seal.

IMG_9450.jpg and


Main gear box assembly completed now for the fitting of the change mechanism

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Need to tap the expansion plug sealing the cross drilling out so the interlock pins can be loaded back into position as you refit the 3 shafts. The plug can be driven in and removed from the reverse gear shaft hole without damage with a suitable diameter drift. It takes a bit of juggling to get the pins in position and the shafts all in the neutral position. Once all is in place the expansion plug can be refitted with some loctite bearing mount to hold it in position.

IMG_9453.jpg and


IMG_9454.jpg and


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to be continued....

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PostPost by: 2cams70 » Mon Nov 23, 2020 10:14 am

Interesting that neither the end face of the Quaife cluster gear and also the copper thrust washers pictured don't have any slots for oil retention. If memory serves me correctly the original Ford ones did (it was a long time ago when I last pulled one down however!)
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PostPost by: rgh0 » Mon Nov 23, 2020 10:25 am

Assembled the gear change selector forks and checked satisfactory selection of all gears. It all looked good. But can you spot the difference between the the gear box before I took it apart and how I assembled it ????. it shows the value of photos as you strip things down. I just should have check them earlier :lol:

gear box before disassembly

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gear box after rebuild

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Note that the 1/2 selector fork I have have put in backwards :roll: The change actually works but you dont get the positive stop as you go into first gear with the selector fork hitting the rear of the casing if you assemble it the wrong way around. This is why the sleeve on the 3/4 selector shaft to also to give that positive stop.
Not a hard fix for next weekend and glad I picked it up now. The manual assembly instruction and drawings do not highlight this risk !

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PostPost by: rgh0 » Mon Nov 23, 2020 11:14 am

2cams70 wrote:Interesting that neither the end face of the Quaife cluster gear and also the copper thrust washers pictured don't have any slots for oil retention. If memory serves me correctly the original Ford ones did (it was a long time ago when I last pulled one down however!)



Original Ford thrust bearings - steel backed with copper overlay bottom, TTR supplied "heavy duty" thrust bearings appear to be a solid brass alloy on top

IMG_9457.jpg and


end of original cluster gear, no oil grooves. Oil hole to aid pumping of oil in the ends and out the hole as the shaft spins

IMG_9459.jpg and


IMG_9460.jpg and



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