Jump to content

Crunching downshift to second


ejparrott

Recommended Posts

My 88 developed a new fault on Christmas Eve, it now crunches on downshifting in to second gear. It was fine in the morning when I drove to work, but by the time we got to Dudley that evening we were having problems with it. I've checked the oil and put in about a pint, and that's made no difference. The box was reconditioned 2.5 years ago by AW Transmissions, and installed during our mini rebuild after our accident 2 years ago. Apart from a reluctance to go in to first there's been no other problems with it until now, although every time I've checked the oil level, there has been a quantity of metal on the magnetic filler plug. The drain plug hasn't been out since it was fitted, that's also magnetic. I run Redline GL4 spec oil in it, I think it's MT90 grade.

What thoughts on whats died?

Link to comment
Share on other sites

Is it any better when warmed up?

Does double declutching help?

My Lt77 does the same sort of thing, but for 3rd, and Ashcrofts reckon it's a naff synchro mesh. I just double declutch for now, which solves the problem until it's warmed up.

Link to comment
Share on other sites

If anything its worse warmed up - I can't be certain, but I don't think it does it at the end of my road, which is the only other downshift to second on my daily journey to work.....that said, I think it does on the return trip when I leave the estate.... Double declutching doesn't make much difference, I've tried it a couple of times and still seem to get the same result. The other suggestion was to raise the revs a little, but that's impossible when also braking.

Link to comment
Share on other sites

Any idea where the oil's gone? It can either have leaked [in which case there'll be evidence] or it could have gone through the intermediate seal into the transfer-box [which would imply the bearings for the gearbox output-shaft might not have been holding said shaft firmly and it's been slopping about and worn the oilseal]

I'd suggest draining the main gearbox oil and listening for that tinkle of metal-bits. You could have ruptured a synchro.

Link to comment
Share on other sites

Our Lightweight did exactly the same thing - all fine when cold, but crunching going down into second once warmed up. It later started just being a bit rough changing down into third and first and crunching when selecting reverse, all only when warm. I tried slipping the clutch to clean the faces and replaced all the hydraulic components in the clutch system to no avail, but somehting was clearly causing the clutch to drag once the engine was warm. It could have been a spigot bush issue.

Link to comment
Share on other sites

Another quick/easy thing to check is the mainshaft nut, in the transferbox.

G.

In my case, that was the first item checked - it was tight and locked, and the oil was clean, there was no excess end float on the shafts and no abnormal noise from the transmission. So, if the nut is tight on yours, I'd recommend investigating the clutch.

Link to comment
Share on other sites

After the last but one main box rebuild on my 109" after stripping 1 1/2 teeth off the layshaft 3rd gear i had fitted new 1st, 2nd, 1st/2nd syncro hub & both baulk rings, it then grated into 2nd on a downshift and was worse when warmed up. I lived with it by double declutching.

To properly double declutch on a downshift you will have to loose the brake while you raise the revs.

Link to comment
Share on other sites

After the last but one main box rebuild on my 109" after stripping 1 1/2 teeth off the layshaft 3rd gear i had fitted new 1st, 2nd, 1st/2nd syncro hub & both baulk rings, it then grated into 2nd on a downshift and was worse when warmed up. I lived with it by double declutching.

To properly double declutch on a downshift you will have to loose the brake while you raise the revs.

or heel-toe them :)

Link to comment
Share on other sites

or heel-toe them :)

Have you ever seen the size of my feet? Heel-toeing is not a option in a serie 2a. :rofl:

Just blip the throttle with the clutch out when double cluthing on the downshift. This will speed up the layshaft and then with the clutch in it will smoothly slip into gear. You only have to take your foot off the brake for a fraction of a second. Dropping the roadspeed down as far as possible before downshifting has two advantages. You don't have to speed up the layshaft that much and you have more time to take your foot off the brake.

Cheers,

Eric.

Link to comment
Share on other sites

Have you ever seen the size of my feet? Heel-toeing is not a option in a serie 2a. :rofl:

the series footwell must be one of the bigger footwells about... haha

i kind of use the side of my foot to rev match when double clutching.

may favorite is double clutch twin sticking with the overdrive i just love it haha

Link to comment
Share on other sites

Dropping the roadspeed down as far as possible before downshifting has two advantages. You don't have to speed up the layshaft that much and you have more time to take your foot off the brake.

Cheers,

Eric.

The lower speed the better it is, a problem of course if pulling loaded up hill. I've not had chance yet to try out any of the double declutching options or to check the mainshaft nut. I've got braking issues and I'm trying to get them balanced before I worry about going!

If you hold the lever in the gate with a bit of pressure for a few seconds, it also seems to be better.

Link to comment
Share on other sites

synchro cone sounds worn to me for sure.

the lower speed before changing down obviously matches the layshaft to the mainshaft better. using a double clutch and blip will also help and most likely it wont ever crunch again if you do that.

have you got the larger drums on the front by any chance?

Link to comment
Share on other sites

they are noticeably harder to balance than the 10" drums

i just usualy balance the 11" drums by trial and error it can take a while but i have never had a balancing problem with my 10" drum system and also never found it lacking in stopping performance.

Link to comment
Share on other sites

  • 3 weeks later...

No I haven't...been trying hard to get The 109 sorted so I can stop using the 88 and really get to the bottom of a whole list of things...so far nothing's changed, and nothing's gone bang....have been driving gently though! If the weather holds, I hope to finish sorting out The 109 this afternoon

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We use cookies to ensure you get the best experience. By using our website you agree to our Cookie Policy