How smooth should an autobox from 1971 be??

Barten

Barten

Active Member
My 3500 1971 has got a 3 speed automatic gearbox. I am not used to drive Automatics, and I wonder if my box need some kind of adjustment. When I put it in drive or reverse, I feel a "shake" in the car. Does anyone know if this can be adjusted and eventually how it is done?
Regards, Barten
 
both my v8 auto's do this when taking up drive and are a bit thumpy when engaging gear - my 2000 auto howver does not make any such noises etc..
 
oh yea - forgot - jack up the back end of the car and make sure the diff bolts (3 off them) holding the diff to the plate are tight - I had loose ones on 2 cars... made problem alot better
 
Thanks for the advise. The idle speed is around 700 rpm. I will check those bolts.
The car went through the MOT yesterday without any remarks, I am pleased!
 
I've had no end of trouble with mine to get it right.

Here is a litany of actions I took to get mine a lot smoother.

Check engine revs... John is right.. I think 600 is the workshop manual revs.

Check driveshaft and UJs for any wear and play, even a good grease up can make a difference.

Changed diff oil (mine was like margarine) with some new EP90 and the workshop manual says Castrol GTX 10/40 engine oil is acceptable.

Check diff mounting, all three bolts should be tight, although there is no torque setting. (I had three very loose bolts)

Check engine mounts, a misalignment will give a very nasty change. (I had two bushes replaced).

Mine is now fine, the key test is a warmed up gearbox, stationary going from D to R. There should be nothing more than a click on selection. No shunt and only minimal noise.

The BW35 is not a very 'subtle' gearbox, at low speeds there will be some selection noise, on throttle, only a slight upchange noise should be noticable. I have heard a BW65 is much smoother. I don't know if a 65 is easily interchangable with a 35.

I normally lock mine in D2 around town, which it's happy to drive in and can easily pull from stationary. I did also use some Wynn's gearbox conditioner to mine which certainly helped smooth out the upchanges.
 
I also select second when I know there's no chance of top being selected smoothly, which only really happens when you can put your foot down, as Rovertron points out, though ours seems to get worse as the car warms up. Our local Auto-specialist reckons the fluid pressure maybe a bit high due to the outercable (BW65) stretching against the nipple on the inner cable over the years & unintentionally adjusting the pressure. As it looks like the cable has never been touched since new, breaking the factory-fitted nipple on the cable off, could do the trick without actual adjustment, though that may also be neccessary. You can't always get the nipple off though, which means a replacement cable. He also said that general gearbox/drivetrain wear would accentuate the problem & I've since found out one of our diff-mount rubbers (the ones in the boot) is worn, so check them too.
Our P6B (BW65) is just as clunky as our P5B (BW35) has always been & both are only smooth under moderately hard acceleration, so I can't say I know of any difference between the two 'boxes
 
My experience with my 72 is that if you get harsh changes when selecting a gear from neutral, it can be very bad for the diff. Some years ago one of my halfshafts was literally twisted off...I put it down to harsh shifting. The auto trans repair place did not want to fit a longer down-shift cable, but in the end I forced them to, just to achieve a smooth change. With slight throttle opened, the changes are pretty good. However get it to the change-up point, then take your foot off the throttle and feel it bang!! For this reason alone I leave it in second when driving around at low speeds, such as in a car park. I'm also VERY aware of the fragility of the Rover diff!!!
 
Yes! If you have to slow as the car's about to select top, that's the worst clunk of all & can't be good for any part of the drivetrain, which is precisely why I lock it into 2nd until you can get some gas flowing under your right foot.
 
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