Lotus Elan

4-Speed Gearbox help please

PostPost by: billwill » Tue Dec 15, 2015 12:48 pm

Chancer wrote:I reckon I too would immediately revert to a long forgotten knack (can no longer find the right word in my mother tongue)



Conditioned Reflex Action.
or Pavlovial conditioning ?

:lol:
Bill Williams

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PostPost by: john.p.clegg » Tue Dec 15, 2015 3:32 pm

not knowing much about 4-speed boxes,but has anyone thought about a weaker detent spring on reverse?

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PostPost by: rgh0 » Wed Dec 16, 2015 12:49 pm

The need to "wack" it out of reverse is a combination of three factors I believe.

1. The load of the shift rail from the gear lever lift spring. If you lift up the lever as you do when putting in reverse to push it out of reverse the effort normally reduces

2. The design of the interlock pins on the three rails means your pushing all the pins across as you come out of reverse and this increases the force needed

3. The whole reverse mechanism is used less than the forward gears i.e. shift rail, interlocks, detent springs lever arm etc. and thus it does not wear or get polished to the same degree and stays more "notchy" in use. Reducing the load on the reverse rail detent spring can also reduce the effort. An overly notchy gear box in any of the gears is often a sign of not setting the detent spring correctly using shims as specified on the each of the shift rails. When done right the gear box goes into gear with a nice perfectly weighted "snick" that matches all the other controls for feel as you drive.

For reverse whatever the reason, it is the heavier load to change out of reverse is the way they normally are as many people have said.

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PostPost by: gus » Wed Dec 16, 2015 1:21 pm

Mine has never done this, nor did my Seven which is the same gearbox with an extension, so while obviously common, it is not right.

I think your shifter ball is too tight, or the spring in the shifter is too strong.

Next time you have the console out loosen the nylon retaining ball and see if the behavior changes.
Mine is actually cracked so I have to be gentle or the whole assembly will come out

Too loose: comes up out of the gate and gets lost when going into reverse
Too tight: cannot lift it up into reverse
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PostPost by: TroonSprint » Wed Dec 16, 2015 2:35 pm

An overly notchy gear box in any of the gears is often a sign of not setting the detent spring correctly using shims as specified on the each of the shift rails.

I have great respect for Rohan's postings as it is obvious that his knowledge of Elans is huge, but I can't understand what he means by the above sentence. I have just sat down with the workshop manual and carefully read through the section on rebuilding the gearbox and there is no mention of any shims anywhere to do with detent springs. Rohan, are you speaking of the three springs and balls that live under the top cover? No shims are shown on the parts diagram either.

When I dismantled the box I didn't take the gear assemblies to pieces as they were obviously in good condition. I dismantled just enough to allow me to remove the layshaft as that had some narrowing where the needles had been running. The trouble is I never drove the car with this gearbox before I took it apart because I bought the car as a pile of parts, so I don't know if it had this "notchiness" when it was last used in 1977. Is there something I should have done when reassembling?

I think your shifter ball is too tight, or the spring in the shifter is too strong.

Gus, I tried unscrewing the plastic cup right out until I could no longer select the gears, then screwing it down the minimum amount to allow operation. This made no difference to the notchy action, or the reverse gear unwillingness to be deselected. Even so I have installed a double gasket under the cup to raise it up a little.

Thanks to all who have replied.
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PostPost by: GeoffW » Wed Dec 16, 2015 6:20 pm

TroonSprint wrote:
I have great respect for Rohan's postings as it is obvious that his knowledge of Elans is huge, but I can't understand what he means by the above sentence. I have just sat down with the workshop manual and carefully read through the section on rebuilding the gearbox and there is no mention of any shims anywhere to do with detent springs. Rohan, are you speaking of the three springs and balls that live under the top cover? No shims are shown on the parts diagram either.


Shims are commonly added to these springs to increase force exerted by the spring to prevent popping out of gear. If too many shims are added and this force is too high, the gearbox will feel "notchy" or difficult to get into gear. I don't think this would be called out in the parts list. In other words - trial and error is recommended out of the car prior to fitting in the car.
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PostPost by: Hawksfield » Wed Dec 16, 2015 8:39 pm

Hi all

The information to check the detent springs is certainly in my workshop manual dated 1974 page 1170
The dimensions should be within .335/.3375in (8.5/9.5mm) measured from the face.
Actually mine were less than this and has all the typical characteristic of notchy gear change and stiff to remove from reverse
I am so used to the box that I had to go and try it after reading this post just to check if mine was the same
I've managed it for over 30 years so it will do !
Regards

John

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PostPost by: rgh0 » Wed Dec 16, 2015 9:20 pm

Yes you need to use shims to adjust the detent spring height to the correct specified dimension.

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PostPost by: TroonSprint » Wed Dec 16, 2015 10:24 pm

I must have a cut-down version of the workshop manual as it doesn't mention any measurement for the detent springs or the use of shims, neither in the Gearbox section or in the Technical Data section. Had I known about such a measurement i would have checked it while the box was dismantled. My manual is titled as follows:
Lotus Elan
Workshop Manual
Lotus Cars Limited, Norwich, Norfolk, NR14 8EZ, England
Telegrams: Lotus, Norwich. Telex: 97401
Part No. 36 T 327
March 1970.

Is this not an official Lotus manual? It certainly doesn't have a page numbering system that goes up to 1170. Each section's pages are numbered from 1 upwards. The gearbox is section F, pages 1 - 18.

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PostPost by: Craven » Thu Dec 17, 2015 1:09 am

I?ve been stripping and rebuilding these gearboxes over the last 40 years and have never found or seen one fitted with shims.
BTW nor do I recall any difference in the arrangement for selecting reverse in any of the variations of this type of box only the addition of the reverse light switch.
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PostPost by: rgh0 » Thu Dec 17, 2015 9:26 am

My 36/T 327 manual on page 18 of the gearbox section under section F5 "Jumping Out of Gear" specifies the dimension for the detent springs above the cover of 8.5 to 9.5 mm and the use of steel shims to achieve this dimension.

as people sometimes say RTFM

cheers
Rohan

PS my gearbox section goes to page 19 that covers a number of further checks if jumping out of gear or hard to select gears
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PostPost by: Hawksfield » Thu Dec 17, 2015 10:20 am

Hi Craven

My box was fitted with shims when I stripped for a rebuild some years ago, they were removed when I had to go into the box again because of flashing on the second syncro ring had to be removed.
It did not improve the notch ness or the removal from reverse gear at all so they are still not fitted and it does not jump out of gear,
Not taking the gearbox out for something that makes no difference
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PostPost by: TroonSprint » Thu Dec 17, 2015 10:31 am

My 36/T 327 manual on page 18 of the gearbox section under section F5 "Jumping Out of Gear" specifies the dimension for the detent springs above the cover of 8.5 to 9.5 mm and the use of steel shims to achieve this dimension.

as people sometimes say RTFM

Rohan, I don't think the RTFM statement was at all necessary. I am perfectly able to read the words and understand them. My manual is obviously not the same as yours. I attach a copy of page F18 of my 36/T 327 manual. Kindly point out to me where it tells me of the detent spring measurements. There is no page 19.

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f18.jpg and
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PostPost by: rgh0 » Thu Dec 17, 2015 10:48 am

Sorry maybe my joke was in poor taste but I was being told it was not in the manual when it was clearly in mine by more people than just you.

Looks like there are a number manual versions some with the jumping out of gear section and some without it. You learn something new every day.

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PostPost by: rgh0 » Thu Dec 17, 2015 10:53 am

my pages 18 and 19 attached

IMG_20151217_0001.pdf
(297.33 KiB) Downloaded 265 times


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