elripster

After spending some time with that grimm jeeper gear ratio calculator I was shocked about just how tall the 2nd gen auto's 4th gear is. It makes no sense to me. While I can understand an auto being maybe 1 ratio lower than the standard, needing 4.88's with 31's when a standard can do it with 4.10's is ridiculous.

This got the engineer in me thinking that instead of bandaiding the problem down stream (excessively low differential gearing), why not take a closer look at THE problem which is that 4th gear is way too tall. That issue will cause lots of forced down shifts and result in severe thermal cycling in the engine due to going from low to high rpms under high load which will encourage head gaskets to blow, heads to crack, etc... It is one thing for an engine to do to a given, even high load, and just sit there but it is another to see these constant spikes. It's like overheating might blow an engine in one shot but sever thermal shock will do it years sooner then if the engine were to just sit at a high load and remain there.

So my question is to anyone who has torn into one of these transmissions, what are your thoughts on having a different gear hobbed for it? (There are lots of gear vendors in San Diego) Maybe make the ratio closer to that of the standard or just sufficiently taller as not to render 1st and 2nd gear too torque-less. My 1st gen with 4.88's, 3.0, and 5 speed could pull hills in San Diego at 80mph with the AC on and 4 people in the truck. With correct freeway gearing the 2nd gen should at least get close to that.

Frank

sswearin1

could you swap in a a340f? that could make it cleaner if it was possible but i don't know all the in's and outs. plus, you could mount a marlin crawler adapter and have crawler gears which can not be used with the a340e.

mt_goat

Hey Frank, long time no see

Yeah that 4th gear is ridiculous, why the Toyota engineers thought the 3.slo should be geared to go 130 mph is beyond me Hell, it can't even hardly pull 70 mph with a headwind lol.

elripster

Don't I know it! Well I'm back and here to stay. It took a while to procure another truck after my 89 was stolen about 1.5 years ago. Now I have a 2nd gen 3.0 auto.

Constantly having to floor the truck to force downshifts is soooo hard on the engine. No wonder the things blow head gaskets!

If I can get my hands on a A340H... or even just the internals... hmmmmm

The A340E has a .71 OD like the H. The F has a .75 which is a little better but I believe still too tall. Intuitively I would think a .82 OD might work well but would need to do the math to be more sure.

I suspect Toyota was hoping they could increase fuel economy on the freeway but the engine just doesn't have the torque. With a larger engine, an OD like that could provide good economy but not with such a small engine.

Frank

mt_goat

Well I just happen to have a good one here
https://www.yotatech.com/forums/f180/good-3-0-auto-transmission-t-case-a340h-oklahoma-107810/

elripster

Wow, that's in good condition. I'd like to find one locally and hopefully broken to get it for free/cheap and save on shipping. I'll keep yours in mind though. Thanks for the offer.

Frank

mt_goat

Yeah for R&D work just look for a bad one, problem is they are too tough to go bad very often.

elripster

You are probably right. I'm just afriad it will never go back together although if I need to test something it should. We'll I'll see how things are looking this summer. I'm very curious to investigate.

Frank