ATF for BW35 Transmission

[bunnspecial]

I have another quality British Leyland rust heap quality automobile headed my way in the next few weeks(working out shipping details). This particular model was not widely sold in the US, and it's estimated that there are fewer than 20, so information on them is scarce. For that matter, Top Gear has destroyed enough of them to make them relatively scarce in the UK compared to how many were sold, but that's neither here nor there.

In any case, the one I'm buying has the Borg-Warner 35 3-speed auto. I'd prefer a manual, and may fit one eventually(fortunately the parts are available from the BL parts bin) but for the time being I'm going to get the full experience with the auto box.

One of the first tasks in getting it roadworthy again will be changing the ATF-I don't have a service history, and the car has set for ~10 years.

The service manual specifies "Type F" transmission fluid. What would be the best modern equivalent to this? Forgive my ignorance also as I have very little experience with servicing automatics, but I know the manual specifies that several pints will remain in the torque converter when only draining the pan(I know this is unusual-I've always been told that flushing is the only way to do a complete fluid "change"). Is there any worry of mixing modern ATF with whatever is left over of what may be the factory fill?

 

[JayhawkRoy]

Here is a discussion from way back in 2003 with some recommendations. A quick search shows Type F is still available if you want to use it. (from Walmart, Adv Auto, Amazon). The link provides several other possible options to update from Type F. Doesn't look like link will work. Cut and paste should get you there anyway.

https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/498948/Re:_Replace__ATF_TYPE_F__with

 

[Rand]

you can use type F, it is readily available I use it in my tractor "fleet".

 

[Whimsey]

Originally Posted by Rand
you can use type F, it is readily available I use it in my tractor "fleet".


The power steering in my 1996 Ford Contour uses Type F, it's easy to get at Walmart or auto part stores.

Whimsey

 

[bunnspecial]

Thanks-Type F it is!

I'll see what it looks like when it comes out of the pan. Looking around, type F seems cheap enough that I could afford to change it a few times in a short period to also make sure what gets left in the torque converter gets diluted/cleaned up as well.

Of course, for all I know, I may drain it and find that it's pink and looks/smells new. The car IS coming from someone who is an enthusiast without the time anymore, so it's possible that he changed the ATF somewhere along the way and just didn't record/remember it(the response I got was "I've changed a lot of the fluids but would plan on changing all of them since I don't remember what all I changed or when I changed them, and they have sat 10+ years"). I'll pay it by ear(or rather look/smell) as to what I actually end up doing, although it will get one drain and fill for my own peace of mind.

I admit to being a little bit afraid of how a detuned, low compression, emissions-choked US spec 1.8L 4-cylinder at 65 hp SAE net does pulling a 2300lb car with a 1960s technology automatic transmission. The listed test I find claim 14s 0-60 and a 93mph top speed, which doesn't seem TERRIBLE given the specs, although I'm also assuming that's with a manual. Fortunately, the engine is shared with a popular sports car, so performance parts are plentiful. Getting the compression ratio up to 9.5:1 is actually straight forward, although does require replacing the pistons.

 

[3311]

Amazing how far engines have come. I have an engine(2.3) in my explorer only a little bigger and it has 4times the power.

Sounds like a cool project!

 

[bunnspecial]

Originally Posted by 3311
Amazing how far engines have come. I have an engine(2.3) in my explorer only a little bigger and it has 4times the power.

Sounds like a cool project!


One thing about these old British 4 cylinders-they don't turn out eye-popping horsepower numbers, but by and large tend to be small bore with a really long stroke. That's a hold over from an old way of taxing that taxed the bore diameter, but as a consequence they tend to have a fair bit of torque at all speeds and especially down low. They're still not going to break any records, but at least the torque, especially in a ~2000lb car(Marinas weigh more than that, but MGBs, where I'm more familiar with this engine, only way a bit more than that) makes them pull away a bit better than you might think.

Once I fix the abysmal C/R of the stock engine in this and get it up to a more reasonable 9.5:1(which requires a piston swap, but of course that also means I'll hone the bores and put fresh rings on it along with rod bearings and 3 of the 5 main bearings to freshen things up a big) I should get it to ~90hp and around 100 ft-lbs of peak torque. I've been advised that-with the automatic-I should advance the cam a fair bit from stock since the AT probably won't let the engine spin over ~4K or so.

Of course, they also shake and rattle so much that you feel like you're going a lot faster than you actually are

Incidentally, in making some phone calls this weekend, I happened upon a previous owner of the car I'm buying-someone well known in the MG community for sticking V8s in MGBs and has put 600K miles on his personal MGB V8 GT. He'd bought it back in the 80s and fixed it up for his mother to drive, and she'd put a fair few miles on it before she died and eventually he ended back up with it and sold it to the current owner. It's fun to get that much history on a car!