Auto gearbox help

[catlotion]

hi,

I've acquired a stag recently and very happy with it. however there are a few niggles (inevitably) that I hope someone can help out with.

• The auto box (BW35) shifts up and down fine without major lurches or clunks from starting but it seems a bit reluctant to go up to 3rd - this only happens at about 40mph. Is there an adjustment needed or is this fairly normal - I read elsewhere that it should be in 3rd around 25mph.
• When I slow to a stop there's often quite a loud clunk from the transmission. It sounds like it's coming from more towards the rear. I did read somewhere that there was always play of this sort in the diff/transmission and not to worry - can anyone confirm this please?
• A previous owner has fitted a makeshift bottle which seems to be acting as an expansion vessel for the transmission fluid(!) - I only noticed it as after a long run it squirted fluid up the inside of the bonnet a bit.It's hose runsdown by the transmission dipstick (somewhere...) I've never seen this- can anyone shed any light on why this may have been fitted?

apologies for long post!

thanks in advance for any help...

Toby

[GDPR]

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Hi Toby - welcome

Have a read of the ROM as to adjusting this kickdown cable, then close the book as you haven't got the pressure adaptor and gauges that I have and do it the experimental way......


Disconnect the kickdown cable clevis pin and try the car with the cable disconnected - on a very light throttle on a flat road the gearbox should go into 3rd by about 18 mph.

If it does, then reconnect the cable and slacken it off so it goes into 3rd at about 22mph.

Switch the engine off and with someone holding the throttle pedal on the floor, check at the carb end that you are getting full throttle - bet you are not......and the kickdown cable had been over-adjusted because the kickdown wouldn't work..... adjust the throttle cable and/or bend the throttle pedal arm until when the pedal is floored, full throttle is achieved.

Take it out for a run and enjoy your better behaved car

If disconnecting the kickdown cable didn't work, then you have problems with the box itself and we'll deal with them later.

Clanging in and out of gear is a Borg Warner issue as the box has no engagement control, but a tickover that's higher than 750 makes it much worse. An over adjusted kickdown can hold the box pressures high and cause the 2-1 shift when coming to rest to be a bit hard hence the bang - make sure that your propshaft UJs are ok as well...

The "vessel" may just be that your box periodically overheats or gets overfilled and he wanted to catch the fluid from hitting the exhaust when it puked - probably nothing in it....might even have the wrong dipstick......

Russ:dude:

[catlotion]

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fantastic - thanks Russ! will try that and see... (will have to be after I sort out the suspect bushes at the front though - worrying knocking noises!)

cheers,

Toby

[V Mad]

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This may not apply to you catlotion but there is a common problem with modified Stags (eg the Rover V8 engine) where the dipstick/filler tube is not at the correct height. This makes the level reading on the dipstick incorrect and may cause overfilling and subsequent dumping of fluid. Another problem is that the breather tube may be blocked/too small and this also can cause fluid dumping.

[catlotion]

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thanks v mad. It's a Triumph V8 and both engine and gearbox seem pretty original (apart from this bottle). I will check the breather to see if it's blocked... any good tips to do this?

I find the levels a bit random - I read that it's ok to have the trans fluid level at the low mark when the engine isn't running, but it's kinda hard to read off as it's pretty clean and thin and doesn't really stick to the dipstick...

cheers,

Toby

[jbuckl]

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The kickdown cable check / adjust is first thing.

Late upshifts can be a sticking governor valve on the output shaft.

It is usually on 1 to 2 and 2 to 3.

Clunking is worse if the box is worn but also if u/j s are worn too.

The governor valve can be removed with the propshaft and rear extension is removed.

It must be meticulously cleaned and refitted.

Good news is BW 35 is cheap to buy reconditioned and the easiest to change.

However spares are not that easy to find now.

Pumping out oil thru breather pipe is usually due to convertor drain valve not sealing.

There is no easy fix for this valve that I know of, because its staked in.

Usually the most oil will leave the box when the car is started and then switched off before its warmed up....caused by the convertor 'drain-down' which effectively overfills the box.
The breather pipe needs to seal well on the grey breather stub...this helps quite a bit as the pipe is long enough to support quite a head of transmission oil.
atb
Julian

[catlotion]

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thanks Julian,

hopefully all is not lost. Apart from late upshifts the car drives fine reallyand the one noticeable clunk is only sometimeswhen you come to a stop (feels as if the rear axle is catching up with the transmission and taking up a bit of play).

The bottle is a bit weird though - maybe it's just a levels thing. The dipstick reads very high when engine running. Maybe I should empty the bottle and see if it fills again? (the car doesn't leak anything on the floor at all)

The other thing I forgot to mention is that I found a bolt on the back of the accelerator that prevents it from reaching the floor - you can occasionally get kickdown but not on demand. haven't a clue why someone fitted this (fuel saving?!) - think my first actions should be to remove this and setup kickdown cable properly and see what happens.

ah - the fun and games of classic cars again!

[Sheepdip]

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Kryten sounds like you've experience of these. I have overhauled quite a few in the past, but currently experience similar problems to Toby, ie late and jerky upshifts.

In the past I've found cleaning the valve block cleared it but not this time. The kickdown is slack and against its stop at idle, I can't make it slacker without modifications. That said if its disconnected change is at very low speed so suspect governor is fine.I've also found that manually shifting back to 2nd then D will shift into 3rd at lower speeds.

I don't want to spend much time on it as going to manual or 4spd auto but am towing to Northumberland and National day and would like to make iit better is easy, so any other thoughts welcomed.

Paul

[GDPR]

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At this point Paul I would be reaching for the pressure gauge and seeing what I had running in the box at idle and light throttle - it could be a sticky throttle valve or a 2-3 shift valve sticking - the governor is a prime candidate for sticking and even the modulator valve could be the issue. Front brake band slack could be making the 2-3 shift rough but won't delay the shift.

I have known the crimped ferrule to move on the kickdown cable too - the ferrule is free when the cable is new, and it's adjusted specifically to that gearbox , set with the pressure gauge on it - you could cut the ferrule off to drop the pressure, but you take the risk that the cable may come out of the snail cam in the box because it's too slack and then you'll have to drop the pan to put it back on - however with care you should get away with it.......

Russ:dude:

[polly]

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hi' im no expert on this but with help from all on here i managed to get mine changing smoothly, the ferrul on mine is missing and i found that the cable was stuck between the bellhousing and tunnel.have you checked the bracket fitted to the carbs? after all the adjusting failed i disconnected the kickdown cable and gently bent down the said bracket so i could connect itall up without pulling on the inner cable,after road testing i found it was changing up and down really great with hardly any clunking at all when sellecting gears,also idle speed is important mine is set atabout 650rpm.

cheers steve.

[Sheepdip]

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Sorry to resurrect this again but I checked my Stag at the weekend, I'd already pulled the ferrule up to the end of the cable, bent the connector slightlyand measured the distance between end of cable and conencting pin as 30mm, how does that compare with others?

Paul

[catlotion]

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just as an update to original post - I've managed to get an acceptable upshift speed by slackening off the kickdown cable. I think it was badly set when the engine was changed as it's right at the bottom of adjustment and I can still get effective kickdown. It depends greatly on throttle position too as it will hold in second if I'm accelerating moderately but drops into 3rd about 23mph ona light throttle.

However, I still get a nasty clunk when coming to a stop and it seems to be only when the box shifts down from 3rd to neutral. If you're in 1st or 2nd and come to a halt it's completely clunk-free... I will check the UJs when I get a chance, but wouldn't that cause an issue on all gears? :?

cheers!

Toby

[Sheepdip]

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Well done. Wish I had the same, theres no slack, to help it I manually shift back to second then to drive on light throttle around 30mph.

Everything clunks on mine to, I wonder if the band adjustment would help as it feels like the gears are competing against each other. Just got to survive the summer, roll on the man/od or 4spdauto!

Just a thought, does anyone know the differences between the 35 and 65 cable in case fitted wrong one in past?

Paul

[Guest]

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This link was posted by someone in the past, sorry forgot name, it may help,

http://www.anugraha.org.uk/rover/bw35/

Don Kennedy