H150 to H152 upgrade (6 Viewers)

[John Young]

I searched but did not find this specific topic in the 70 Series forum. Hoping you all can spot flaws in what I am thinking about doing.

I have a mid-90's 1FZ-F Troopy with an H150 transmission in it. I prefer low revs on the highway even if I go a little slower. I've a buddy who spent a fair amount of time driving it at 150+ KPH in the desert and he had no particular issues but I am the kind of guy who just likes the engine to putter along at 2200-2400 so I am thinking seriously about trying to convert the H150 I have into something close to an H152.

I'm starting to use AI to help me figure this out, which might be a mistake. Gemini gives the following table:

ChatGPT initially gave me obviously wrong data but I asked it to check its work and this came back:

I've been told (by people) that most everything that fits in an H152 should fit in a H150 case. I get mixed answers when I ask AI's the same question. But after a while they seem to agree that it is possible and that I won't need to machine the H150 case.

Terrain Tamer has a 1000 USD kit, but I'm inclined to give Toyota OEM parts a try.

The H1f5 is used in the VDJ76 78 and 79. Using the usual sources I get the following part numbers:

H152 Countershaft: 33421-60230

H152 2nd Gear: 33033-60060

H152 5th gear: 33036-60020

The cost of these three parts seems to be substantially less than the Terrain Tamer kit.

Does anyone out there see flaws in this logic?

 

[Hulsty]

I would say there are numourous small internal differences, everyone here justs buys a whole H152, swaps the required parts for their engine and off they go

 

[John Young]

So we've gone pretty far down the rabbit hole on this one. Taken the box completely apart for new bearings, taller 5th etc. As part of that we bought a new lay shaft and that has the better 2nd. But this requires a different 2nd synchro. We've tried a couple of part numbers without luck so far.

I happen to have access to the Terrain Tamer upgrade kit just to look at, and it is not just a repackaged Toyota part. The casting is different and 2nd appears different as well. The TT kit, which is pretty pricey, comes only with the lay shaft and the taller 5th so I suspect they reengineered the lay shaft to use the standard 150 2nd gear setup.

Here's the new lay shaft we are using on the left

The original gears appear in surprisingly good shape considering 500k km in a heavy troopy schoolbus