Overdrive button.....not what you're expecting!

[Mart]

I have just been talking with a mechanic friend of mine about the number of gears in my '94 3.0l surf. I asked him why there seems to be 5 gears in a 4 gear auto box. When turn off overdrive you have the expected 4 gears. However, when I re-engage overdive in what I think is 4th gear there are two further gear changes until top.

The answer : he says there is only four gears when the o/d of off, but when its re-engaged two more gears come into play changing the ratio of 3rd and 4th hence the two further gear changes when o/d is turned off when driving.

Any comments ? The certainly seems to be the case as I am pretty sure there isn't a 5 gear auto box in the '94 model.

Answers on a post card!

[Morr]

I have just been talking with a mechanic friend of mine about the number of gears in my '94 3.0l surf. I asked him why there seems to be 5 gears in a 4 gear auto box. When turn off overdrive you have the expected 4 gears. However, when I re-engage overdive in what I think is 4th gear there are two further gear changes until top.

The answer : he says there is only four gears when the o/d of off, but when its re-engaged two more gears come into play changing the ratio of 3rd and 4th hence the two further gear changes when o/d is turned off when driving.

Any comments ? The certainly seems to be the case as I am pretty sure there isn't a 5 gear auto box in the '94 model.

Answers on a post card!

Sounds about right to me, traditionally on manual boxes with overdrive thats exactly what happened, with o/d selected the 3rd & 4th gear were raised higher.
The auto box on the surf would still be considered 4sp with o/d. I must check/listen to my own more carefully, as for some reason I thought it was 3sp with o/d , don't pay that much attention to the number of shifts to be honest

[Jonnyboy]

I had an old V8 landrover with a manual overdrive. You could bring it in with every gear, i.e 1,1+o,2,2+o etc, theoretically giving you 8 forward gears - or 16 if you count low box.

You could even use it on reverse. I think the principle is not to think of it as the equivalent of a fifth gear

[stara]

manual o/d and auto o/d are different, on a manual it is either an additional 'gear' or an external 'box (landrover, fairey), on an auto it isn't really overdrive, it just allows the transmission to select top which is a 'locked' gear, the 1st 2nd 3rd ratios are variable. (this is why an auto box gets hot, due to slippage in lower gears esp when towing up hills)

[kiwi-jim]

I have just been talking with a mechanic friend of mine about the number of gears in my '94 3.0l surf. I asked him why there seems to be 5 gears in a 4 gear auto box. When turn off overdrive you have the expected 4 gears. However, when I re-engage overdive in what I think is 4th gear there are two further gear changes until top.

The answer : he says there is only four gears when the o/d of off, but when its re-engaged two more gears come into play changing the ratio of 3rd and 4th hence the two further gear changes when o/d is turned off when driving.

Any comments ? The certainly seems to be the case as I am pretty sure there isn't a 5 gear auto box in the '94 model.

Answers on a post card!

with o/d off its a 3 speed auto, with o/d on its a 4 speed with lock up torque converter hence the feeling of a 5th gear. in normal mode our truck hits 4th gear and locks the converter at the same time, but in power mode it hits 4th for a few seconds before locking the converter, so from a stand still there are 4 distinct shifts-like a 5 speed.

[Morr]

with o/d off its a 3 speed auto, with o/d on its a 4 speed with lock up torque converter hence the feeling of a 5th gear. in normal mode our truck hits 4th gear and locks the converter at the same time, but in power mode it hits 4th for a few seconds before locking the converter, so from a stand still there are 4 distinct shifts-like a 5 speed.

Aha.. that sounds about right