A well setup manually operated jatco or trimatic is as heavy as a 71C box but they let you put more emphasis on momentum and driving without wrestling a gearbox with clutch in dirt racing and possibly in drifting. Not as good as sequential manual but still cheaper than rebuilding rare 56/60 series 5 speeds. Heres a TH400 getting some love
http://www.youtube.com/watch?v=8IpPVF ... ture=youtube_gdata_player

well you wouldn't need a five-speed for driving or dirt racing. Just a four speed.

Are there any advantages over the 4-speed?

Due to the lightweight and torque you only need a 3 speed TH400
2.48, 1.48 and 1:1 is plenty for a Buggy/sandrail with big power
Lightweight datsuns are like buggys when they have enough oomph! :)

Those Jatco boxes are quite impressive. I stripped one today (for scrap) with around 220kms on it. There was a bit of wear on the band, but the frictions were like new. It was only pilled for a manula conversion because it had a blown modulator diaphram.

what dirt racing you referring too?

overdrive 5 speed is great as it enables you to run 4.9 ratio diff and still hit 150km/h

auto in drift = no clutch-kicks, no engine decell in trasitions etc
auto in rallying means less driveline control over the rear of the car in decell as well. For big open high speed courses like Bajas, well that's not such an issue.

If you're talking about an auto instead of rebuilding rare 56/60 series 5 speeds, forget it. You'd loose too much power from the little A series to be anywhere near competitive.

A mate who used to be seriously into drag racing his old L series powered 240Z tried an auto after getting stuck on 12.9 with the manual. Went slower and lower mph because the trans sapped too much power, even after experimenting with diff ratios and different stalls etc

That was Baja racing off road all out suicide sprints!

A well setup full manualised auto can be enough for most street duties behind a boosted A series whereas a 60 series box will live a shorter time and no longer be rebuildable over time due to NLA parts.

In drag racing a well setup auto will beat a manual hands down but the auto sapping power in any engine is due to the wrong setup and there are only few companies like KEAS that really know the Jatco auto. The Jatco is used in all kinds of cars successfully in 1/4 mile racing. Move futher up the auto food chain and there are liberty boxes and other specialised autos for strict straightline duty. Many full on rotaries are using the Jatco successfully over supra and other manual boxes and there are even some Kiwis with 2ltr turbo setups using it in circuit racing with the correct mods and doing well, I cant find the forum it was in atm will keep looking.

Ive had a full manualised Jatco in my Rx4 in the past and it was easy to control for decel but not compared to the control a manual had but it was perfect for street & strip. It had larger oil passages, modded synchros and valve body modded for less abrupt engine deceleration and I even managed with ease to control slide in the wet.

For massive wheelspin and response the valve body can be removed and accumulators modded with inserts or harder springs for chirping in every gear :) It fully manualises the auto like a shift kit does but cheaper. Diahatsus autos on the 993cc hatches till 1991 had no valve body and where a full semi auto setup similar to earlier Hondas.

if/when I rebuild The Defect III, I'm debating going back to a 3N71B, as the gearbox in it is a 60L four speed and I was drivng that gearbox hard in the original defect and cracked one of the exhaunt mounts off the back of it - it uses the exhaust hanger position to mount the gearbox into the car, and I broke an engine mount in THe Defect too... hover I've notived the 60L 4 speed is starting to not like being put in reverse sometimes, and an thinking it's in the early stages of stuffing up... asnd Celica 5 speeds are a dead option, which leaves the 3N71B...

as for collecting 60L four speed gearboxes.... only ever came across one, and I was actually shoucked when I found out it is an A14/A15 gearbox.... as junior stock cars are supposed to run 56A gearboxes - gearbox is out of a junior stocky 120Y)

Totally agree the 60 series is a no go, the sillibox is a no go and theres not much left that isnt rare and chased by everyone else. A 3.7, 3.545 or 3.31 will be perfect behind a modded tricked 3n71 for most duties behind a boosted A.

Love a sequential 4 speed with 2.6, 1.75, 1:1 and .75 as strong as a T50 yota box
but it will only happen if there is a new racing class to suit it.

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massive generalisation. It's not true for lower power applications. Rob's 240Z (tripple 40mm sloex L28 at 2850cc) ran 12.9 at a low 105mph with the manual. That's a very good time for the mph. All the drag racing gurus told him an auto would be the best way to go faster, but after many attempts with a built Jatco, various stall and diff gears, he couldn't get within 5mph and 3 tenths of his PB. Its not like it wasn't properly built or that he didn't try the right combo, it just couldn't match the well driven manual. There's a big difference between eeking out every little bit of a low powered car and dedicated drag racing rotaries, so be a bit careful applying generalised drag racing wisdom that autos are better to a little <1600cc 4cyl... even with turbo

How much power do you (realisticly!) think your turbo A series will make? 3spd auto and mid 3 diff gears behind a turbo A series beat a manual equivalent down the quarter? only if the manual breaks, which is a good chance I suppose... Unless you're going to be running low 12's there's not going to be a performance advantage to be had from an auto, other than consistency.

then there's the cost of this manualised auto!