90 Autobox strange behaviour

[jonnyboy54321]

Evening all, have dipped in and out of the forum on a few occasions to keep my hand in so to speak. like the new look! There may be a 120 on the horizon that I have lusted after for years and years if I can sell the Mrs to pay for it

A pal of mine recently acquired a 95, its a d4d one with about 200k on it.
There's an issue with the autobox - overdrive doesn't function, prev owner reports it performs better if warmed up for a minute first otherwise it struggles to engage drive. Gears change perfectly on light throttle (preferably with a bit of backing off as its ready to change so it "drops in" so to speak. Now, prev owner used for towing but did 25/30 k miles and it has never changed ie deteriorated. Has had at least one ATF change possibly two in that time, my understanding is that the correct fluid was used.

He's not keen to automatically write off the box as u/s bearing in mind its "always been like that" - and I do see his point. Anyone heard of anything like this? Possibly from an electrickery/adjustment perspective? It goes without saying that he's been encouraged to sign up here - although i will end up having to show him how - he does screwdrivers not a mouse!!!!!


Thanks in advance.

 

[Beau]

I had a similar issue years ago, and it was a earth wire not attached properly. This wire specifically is earthed on the side of the oil filter housing on my 1KZ, I'd guess it should be pretty similar on the D4D lump. However, with that said, it's best to check all the earth wiring.

Now the fact that it performs better when warm does tell me it's not an electrical problem though and more mechanical. How is the Torque converter, have you performed a stall test on it? Foot, on break, Give it throttle and it should read a certain RPM (nor sure what), but I reckon no more than like 2400rpm or abouts...

If you manually control the box by shifting from L 2 D does it behave any differently? Has the truck had any other problems in the past like coolant in the box ect?

 

[jonnyboy54321]

That's interesting Beau. He is drawn to it being electrical, partly due to o/drive being inop. In terms of it being warm - the one standing minue if from cold ie first run of the day, and only a minute or so.
No news on coolant into ATF, prev owner had it 4/5 years, 25 or 30k, always been same in his ownership.
I'll mention stall test.

 

[AndyCook]

I think The overdrive doesn't kick in until the gearbox has reached a certain temperature. I have noticed his when I had a Colorado and in my auto hilux. After driving a few miles at normal cruising speed I hear it drop into overdrive and the rpm drops down. On really cold icy days i find I have to drive further before this occurs. So it could still be electrical issue ?

 

[Beau]

Interesting Andy, I don't believe mines ever behaved like that, or maybe I've never experienced temps that cold... but back home in Milton Keynes it was under a minute out of my development and then the open carriage ways which were done at 60mph+ and I always recall getting into OD

 

[jonnyboy54321]

Interesting, very interesting. Will have a word with him today about the filter earth etc. Thanks so far guys.

 

[goodoldboy]

I think The overdrive doesn't kick in until the gearbox has reached a certain temperature. I have noticed his when I had a Colorado and in my auto hilux. After driving a few miles at normal cruising speed I hear it drop into overdrive and the rpm drops down. On really cold icy days i find I have to drive further before this occurs. So it could still be electrical issue ?

yes mine does the same Andy & I think it mentioned it in the manual.I'll try & find the manual later & look it up

 

[goodoldboy]

yes mine does the same Andy & I think it mentioned it in the manual.I'll try & find the manual later & look it up

yep P195 of the manual the O/D won't switch until the engine coolant is up to temperature.

 

[jonnyboy54321]

So I have queried the overdrive - it's only being used urban at the moment so that could be a red herring.
Anyone had any experience of a dicky autobox that has a fault yet not deteriorated at all for years/30k miles? It does make me wonder - anytime I've had a box fault on anything it's got worse over a period of time, not stayed the same.
Are these boxes controlled by any signalling ie electronically? Just wondering if the 'box is not getting correct messages therefore hesitant to change or whatever..
Thanks so far !

 

[jonnyboy54321]

Only just realised i never updated this thread - sorry - issue resolved by a proper ATF & filter change, twice, and a thorough clean of all electrical connections, including all main earths. So I cant definitively say what it was fixed it a - as my pal isnt sure either - however it looks like Beau was partly on the right track - thanks so much!

 

[Beau]

Glad it was a relatively cheap and east fix! All it needed was some attention