Lotus Elan

4 Speed Gearbox rebuild

PostPost by: rgh0 » Sun Sep 13, 2020 8:18 am

After around 15 years of competition since the last rebuild the Quaife straight cut gear box in my Elan needs a refresh. I decided to build up a second competition box and swap out the current one so I would have a spare. I was also interested to try the Quaife helical close ratio gear set and see how noisy it is compared to the straight cut box and the original Elan box

I have a couple of old Cortina boxes sitting on the shelf that I picked up from wreckers about 20 years ago before they became scarce and expensive that will be donors for the rebuild so the first step is to dismantle these to see what the condition of the parts I will need to combine with the new Quaife gear set.

The first box ( black) has a remote extension but otherwise is externally the same as my current box except for a couple of ribs that were added on top of the later bell housings, a couple of ribs were removed internally when this was done

IMG_8987.jpg and



pulling off the major components so I can get it onto the workbench

IMG_8988.jpg and



Having a closer look at it. It has the larger 17mm spigot bearing shaft and the draw nut main shaft

IMG_8992.jpg and


IMG_8991.jpg and


Pulling out the change rods, taking care to collect the 3 springs from the top cover, the 3 detent balls and the 3 interlock plungers.

IMG_8995.jpg and


IMG_8996.jpg and


A bent piece of wire is handy to get the interlock plungers and balls out of the holes

IMG_8997.jpg and


once the change rods and selector forks are removed. The rear extension can be removed. These always seem to stick solid and need careful wedging apart by tapping in the join with a sharp screw driver

IMG_9007.jpg and


more to come.........


cheers
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PostPost by: Bits » Sun Sep 13, 2020 6:31 pm

Looking forward to this.
Gearboxes have always been a mystery.
I hope to drop on one one day to have a look.
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PostPost by: 2cams70 » Mon Sep 14, 2020 9:29 am

The non ribbed box is Mk1 Cortina. The ribbed box is the Mk2 Cortina 2000E type box. The later box has quite a few internal improvements compared to the earlier box. Main shafts and synchro hubs for example are also different. I'm not 100% sure if they are interchangeable.
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PostPost by: rgh0 » Mon Sep 14, 2020 9:45 am

2cams70 wrote:The non ribbed box is Mk1 Cortina. The ribbed box is the Mk2 Cortina 2000E type box. The later box has quite a few internal improvements compared to the earlier box. Main shafts and synchro hubs for example are also different. I'm not 100% sure if they are interchangeable.


Thanks for confirming the Mk1 cortina versus Mk2 cortina bellhousing and thus gearbox as i had suspected it was that based on the pilot bearing spigot diameter difference

Yes I need to reuse synchro hubs / change rods and forks from my old boxes to use with the new Quaife gear sets which come with new shafts and all other gear bits needed . The differences in synchro hubs versions is not clear and something I will need to research once I get my 2 old gear boxes fully to bits to understand what is compatible or not with the Quaife gear sets. i always wanted to get a better idea around the issues of parts interchangeability across the various ages of three rail "2000e" boxes and now is my chance :lol:

I would guess "promotor" knows more about this stuff already and will contribute here as he does lots of diffs and gearboxes

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PostPost by: elangtv2000 » Mon Sep 14, 2020 2:08 pm

rgh0 wrote: The differences in synchro hubs versions is not clear and something I will need to research once I get my 2 old gear boxes fully to bits to understand what is compatible or not with the Quaife gear sets. i always wanted to get a better idea around the issues of parts interchangeability across the various ages of three rail "2000e" boxes and now is my chance :lol: Rohan


Hi Rohan,

I've rebuilt 6 'boxes - 4 early Cortina types and 2 later ribbed types, and have 2 more and lots of parts waiting for me to get to. The synchro rings are just one of several differences; snap ring vs. circlip main shaft, synchro rings, blocker bars, synchro hubs, and no doubt more that I've forgotten since it's been a few years since I've been inside one.

There was a time when new replacement early type synchro rings were hard to find or very expensive. It was often the practice to modify the newer style synchro rings to allow the early blocker bars to fit, and to work with the early gearset assemblies.

I've no experience with Qaife gear sets, but found this thread:
viewtopic.php?f=37&t=38943
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PostPost by: brettengelaz » Tue Sep 15, 2020 7:54 pm

I've successfully modified the "new" synchro balk rings to work with "old" style hubs. Two modifications are needed, first the outer diameter of the smooth section needs to be turned down aprox .100 and the three slots cut fully through. Since I have access to machine tools this was cheaper than upgrading to the new style hubs. A modified ring is on the left with an original "new" ring on the right. I don't have an unmodified ring or I'd provide the exact measurements. Hope this helps.

Lotus 2000ESyncros.jpg
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PostPost by: nmauduit » Tue Sep 15, 2020 9:38 pm

brettengelaz wrote:I've successfully modified the "new" synchro balk rings to work with "old" style hubs. Two modifications are needed, first the outer diameter of the smooth section needs to be turned down aprox .100 and the three slots cut fully through. [/attachment]



iirc the cone angle is not the same (5° vs. 6°? )
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PostPost by: rgh0 » Sat Sep 19, 2020 4:41 am

Continuing with the dismantling of my 2 spare boxes

Pulling out the mainshaft ( earlier draw nut type) and input shaft ( 17mm spigot diameter type).
The synchro hubs came in two spline sizes early 1.20 inch and late 1.29 inch on the main shaft. Which I presume also corresponds to the synchro ring changes. I will explore this once I get the main shaft apart as you cant tell from input shaft spigot size and main shaft draw nut style as they applied for both style synchro hubs according to the Dave Bean manual. The later post 1970 snap ring shafts had the later style 1.29 inch spline synchro hubs which I think the Quaiffe gearset main shafts also use... clear as mud.

IMG_9009.jpg and


IMG_9011.jpg and


IMG_9012.jpg and


IMG_9013.jpg and



Removing the cluster gear by driving out the layshaft and collecting all the loose rollers ( 40) and roller washers (4) and thrust bearings (2)

IMG_9016.jpg and


damage to roller bearing surface of layshaft so not reusable which is often the case when you open these up. Luckily I have a couple brand new and a couple of good used layshafts available for the rebuild so not a problem

IMG_9017.jpg and



Now to do the same to my spare "red" gearbox. This was sold to me as incomplete without the change rods and forks mechanism and front seal carrier. I bought it mainly for the centre case as the layshafts tend to vibrate and fret in the locating holes under racing loads enlarging the holes and ultimately leading to gear misalignment

IMG_9018.jpg and


IMG_9025.jpg and


IMG_9028.jpg and


All the bits of the two gearboxes... now need to explore the detail differences and select the best of the components that are needed to rebuild a box with the new Quaiffe gear set that should be delivered next week according to the tracking after I paid the import GST and customs charges.

IMG_9029.jpg and


cheers
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PostPost by: Craven » Sat Sep 19, 2020 8:27 pm

This is the last type and stiffest of the 3 rail cases, recognised by the large round magnet fitted in the bottom section.
3 rail case.jpg and
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PostPost by: rgh0 » Sun Sep 20, 2020 4:47 am

nmauduit wrote:
brettengelaz wrote:I've successfully modified the "new" synchro balk rings to work with "old" style hubs. Two modifications are needed, first the outer diameter of the smooth section needs to be turned down aprox .100 and the three slots cut fully through. [/attachment]



iirc the cone angle is not the same (5° vs. 6°? )



Not sure about any cone angle change. The Dave Bean Manual says the later and earlier synchro hubs can be changed provided the correct matching synchro rings are used and that the hubs match the spline diameters on the main shaft ( which changed for the 1/2 hub in 1967). This implies the cone angles on the earlier and later gears was the same. I will explore this further once I get the Quaife gear set.

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PostPost by: rgh0 » Sun Sep 20, 2020 5:45 am

Dismantled the shafts on the 2 wrecker gear boxes I have, to determine what they have come from and whether I have enough suitable bits for a rebuild using the Quaife gear kit and new gaskets and bearings.

Most would come apart with gentle tapping if needed with a soft plastic headed mallet on the shaft end while holding the component on the shaft in a gloved hand, including the main shaft bearing which appears to be a light push fit on the main shaft. Just need to remember to remove the somewhat hidden ball in the shaft that located the 1st gear sleeve to stop rotation in order to remove the 1/2 synchro hub on the early 1st gear sleeved main shafts.


The input shaft bearings and one of the 3/4 synchro hubs that was tighter fit than normal needed to be pressed off using a bearing splitter and press.

IMG_9043.jpg and


IMG_9044.jpg and



With every thing apart I could measure up the components and compare to the excellent dimensioned drawings in the Dave Bean manual. There are multiple variations in gear and synchro components some which can be exchanged to other gearbox variations and some which cant plus variations in input shaft seal and input shaft spigot size.

IMG_9046.jpg and



The photo above compares the two shafts out of my spare wreckers gearboxes with the old main shaft from my 1968 Elan gear box which currently has a Quaife gearset in it that was installed in the 1990's

The two gear boxes I have are both early wide ratio Cortina boxes pre 1966 . Both have the sleeved 1st gear and the resultant smaller diameter 1/2 synchro hub spline of 1.20 inches compared to the 67 to 70 draw nut version and 70+ snap ring version which did not have the first gear sleeve and used a larger 1.29 inch spline for the 1/2 hub. My original 68 Elan shaft in the photo shows these differences. The Quaife gear set uses the later 1.29 inch spline for the synchro hub so I will need to source a later synchro hub . These hubs came in two versions using the earlier synchro rings for the draw nut version and later synchro rings for the snap ring version so I will need rings to match the hub and rings that I source. Provided the rings are matched to the hub and the splines match on the shaft they are apparently interchangeable on the main shaft and gears.

Another key variation is input shaft spigot size with one of my pre 66 wide ratio Cortina boxes having a 17mm spigot and the other 15mm. Supposedly according to the Bean manual the 15mm spigot was used on semi close ratio boxes and 17 mm on all wide ratio and early close ratio boxes with the outer bearing / oilite bronze bush diameter varying with the 4 bolt ( 40mm) versus 6 bolt (21mm) cranks. Why one of the pre 66 wide ratio Cortina boxes I have came with a 15mm spigot is not clear. Maybe it was used with a later engine at some stage and the input shaft changed as the17 mm spigot require a special and thin walled and fragile oilite bush to fit into the 21mm hole in the 6 bolt crank.

The other key variation is the input shaft seal and housing as there are two housings one that suits a 1 3/8 inch seal outer diameter and one a 1 5/8 inch outer diameter. The housing I have from the wreckers suits the 1 3/8 inch outer seal while the one in my current Elan gearbox suits the 1 5/8. The inner dimension of the seal is 7/8 inch on earlier gear boxes and 1 1/16 inch on post 69 gear boxes. Not sure what seal the Quaife one uses but I have an overhaul kit from TTR coming with the gearboxes with all the required seals and bearings so I will see if the seal housing fits


After all of this it looks like I will need a new 1/2 synchro hub and rings and maybe a new front seal housing but the rest of the bits I have are enough to build a complete new box. I will confirm that when the Quaife kit arrives hopefully tomorrow.

cheers
Rohan
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PostPost by: nmauduit » Sun Sep 20, 2020 9:47 am

rgh0 wrote:
nmauduit wrote:
brettengelaz wrote:I've successfully modified the "new" synchro balk rings to work with "old" style hubs. Two modifications are needed, first the outer diameter of the smooth section needs to be turned down aprox .100 and the three slots cut fully through. [/attachment]



iirc the cone angle is not the same (5° vs. 6°? )



Not sure about any cone angle change. The Dave Bean Manual says the later and earlier synchro hubs can be changed provided the correct matching synchro rings are used and that the hubs match the spline diameters on the main shaft ( which changed for the 1/2 hub in 1967). This implies the cone angles on the earlier and later gears was the same. I will explore this further once I get the Quaife gear set.

cheers
Rohan


you're right indeed... I digged my DB catalog and could not find any reference to cone angle change:
20200920_113046.jpg and
DB gearbox1

20200920_113133.jpg and
DB gearbox2

20200920_113155.jpg and
DB gearbox3

20200920_113208.jpg and
DB gearbox4

20200920_113215.jpg and
DB gearbox5


so I where I would have gathered this impression ... and it is from Lotus 5 speed gearboxes (I have an early version with 5° baulk rings, which I got overhauled in 2014, while the late version is 6° I understand)
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PostPost by: 2cams70 » Sun Sep 20, 2020 2:22 pm

rgh0 wrote:Supposedly according to the Bean manual the 15mm spigot was used on semi close ratio boxes and 17 mm on all wide ratio


That part of the Bean manual is not correct. The bearing sizes (and all other components except for the gears themselves) has nothing to do with whether the box is semi close or wide ratio and everything to with the production year. All of the latest design synchro hubs, etc. can be found in the 1968 onward Mk2 Cortina single rail box.
I used to know all the details quite well but memory is fading on some items in the intervening 25 years or so since I last played around with this family of Ford gearboxes!
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