1990 3.9 4spd auto prob

[Lumbering Jack]

Hi Guys, 

Just picked up a 3.9 EFI auto on a G reg which is going to be donating it's engine, box and gas to my 110.  I knew when I bought it that there was a problem with either the gearbox or torque converter - for what I paid for it I wasn't too fussed though.

It does drive under it's own steam but is quite noisy (grating/scraping but not all the time) from what sounds like where the T C would be and when you put it in gear (R,D 1,2 or 3) it makes a fair clunk as it takes the drive up.  Apparently it won't change up into 4th either.  All these symptoms developed at the same time - we were out laning at the time - and also the gearbox oil got quite hot.  He ended up getting the AA out to carry him home as 3rd was making it very, very  thirsty!

I'm not going to try and pretend to know where to start diagnosing on Autos so just wondered if anyone had any thoughts as to where to start?  Was going to drop the fluid and put fresh in to start but can't really see that achieving much  :-k

What's evryones thoughts?

[Range Rover Blues]

Something inside has gone bang, time for a new box (my first thought).

When it comes apart check the flex plate on the T-C, it wouldn't stop it going into 4th though, that sounds like an oil pressure problem.  The oil pump is driven by the outer shaft from the T-C into the gearbox.  You can check the oil pump pressure somewhere on the front end of the gearbox.

But it might be easier to source a S/H box and fit that whilst it's all in peices.

[Lumbering Jack]

Something inside has gone bang, time for a new box (my first thought).

When it comes apart check the flex plate on the T-C, it wouldn't stop it going into 4th though, that sounds like an oil pressure problem.  The oil pump is driven by the outer shaft from the T-C into the gearbox.  You can check the oil pump pressure somewhere on the front end of the gearbox.

But it might be easier to source a S/H box and fit that whilst it's all in peices.

Thanks RRB,  all help greatfully received  :D  Had been hoping to be this far months ago but due to a few bits and pieces am behind schedule.

if it needs a new box do i need to get the torque converter and box off the same vehicle?

i'd noticed in a few threads about additional oil coolers,  do you think theres a possibility it could be linked to when the oil got too hot?

[Range Rover Blues]

The T-C is standard on all the ZF 4 speeds, you can swap them but be carefulengaging the 3 seperate drive members when you install it into the box, if you try to bolt it to the engine with one not engaged you bust the box.


I don't know how much a new T-C is but sometimes it's suggested you swap it, if there has been any contamination of the oil in the box, bin the T-C as a precaution, you can't clean them out.

Oiol coolers, well on the return feed (low pressure) the oil is circulated through the hot end of the rad to helop it heat up, then through an oil cooler ahead of the rad to cool it back down, sounds daft but the 2 are important.  My LSE has a 3rd, a kenlowe oil cooler under the front chassis member direclty before the oil returns to the 'box to help it keep cool.  I tow a lot, I don't off road it and it's got a big lump under the bonnet which puts strain on the gearbox.

I was told the Merc van (pre sprinter) had a really useful oil cooler on the engine that you can fit to a RRC auto, but I had a touring holiday booked and the Kenlowe rad was only £105.
 

[Lumbering Jack]

Thanks again RRB for the pointers, one more little question:  Would you suggest putting the standard ratio defender transfer box on or a disco one?  I'll be running 265/75/16 (possibly 33's eventually) and it'll be doing a bit of everything.  Possibly some towing but not very often and most likely on the motorways.  I do also have the really low ratio box of the old 110 but was guessing too low.

[Range Rover Blues]

With big tyres go for the low ratio, whilst the RRC B-W type is nice on road you're better of with the LT230 off road anyway as it has the diff lock.

If you go 33s you might want to keep that super low ratio to one side for later.

Auto will help cope with too high a ratio but will work best when matched with axles and tyres etc.