Auto Gearbox - Water Cooled into Aircooled??

[akroblade954]

Hoping some one may know the ansew as I have been googling for days!!

I have a water cooled DF engined 84 T25, which has had a £1,000 gearbox rebuild on its auto box about 10,000 miles ago. I also have an Aircooled, CU engined T25 with an auto box.

Question is, are the two gearboxes inter changeable between the air and water cooled T25's? I want to swap them over as considering parting out or selling the DF engined waterholes T25.

If the whole gearbox is not interchangeable, are individual parts interchangeable? Eg torque converter

Thanks in anticipation of someone knowing the answer for definite!!

[123-jn]

I'm pretty sure they are interchangeable but I bet the ratios are slightly different. I'm sure Aiden will know but I bet they are not different enough to notice too much. The engines have pretty much the same power output so there may be no difference at all?

[akroblade954]

Thanks for the reply. I did PM Aiden before posting, but he doesn't have much experience in the auto box's. Expert on the manuals though and really helpful

I am amazed how little info there is on them on the net. Baring in mind they were fitted to loads of VAG motors, there is almost no info

As Aiden suggested, I probably will have to pull both out and compare side by side.....

[akroblade954]

Struggling with this one!! Don't want to have to take 2 gearboxes out for the sake of it. Must be someone who has tried it or knows the answer? I know WC and AC manual gearboxes aren't a straight swap, but little info on the auto

[123-jn]

Right I seem to have found some info on this, The gearboxes are the same apart from
1. air cooled did not have the oil cooler attached to the front of the autobox, watercooled did.
2. air cooled and early water cooled were the same ratios
3. later watercooled had higher ratio second and third gear
Aircooled WATERCOOLED
1st 2.55 2.71
2nd 1.45 1.50
3rd 1.00 1.00
Reverse 2.46 2.43
Hope this helps, I'm guessing this makes a swap not a very good idea, I reckon the cooler is vital with a bit more power and torque and the slightly higher ratio is better also, although hill climbing may be improved with the Aircooled box?
Final drive is the same in both 4.09 : 1.
There were also some modifications inside in the later box with various valve upgrades and a more powerful springplate in the forward clutch. I'm afraid I haven't a clue what that means or what it does.

[akroblade954]

Great info thanks. Where did you find that?? I think I need to find out the gearbox codes on the 2 buses so I can at least check the ratios. As it happens, the water cooled one is a 60bhp DF engine, so the air-cooled CU has more power and torque!

[123-jn]

The figures I quoted compared the CU and the DG engined vehicles, I think from what I remember the DF engined ones were the same ratios as the cu. The gearbox code NH was used for the higher ratio version. The earlier box was the NG fitted up to 1982 oct. all gearboxes are code 090 .