Differential swap?

5th gear from the RX7s will swap onto the input and output shafts of the B series 5spd. I am using the 5th gears from a Bongo Diesel transmission, gives me a 0.701 5th gear (versus the stock .858 of the B series.) I have no idea what the final GR is using the RX7 gears though, as I don't know the tooth count of those gears. I would not be surprised if it were the same as the bongo's gears.

+1 on the swap to taller tires. Go to a taller tire and you will drop rpms - speedo will be off, of course.

Here's a tire calculator to see what % you'll be off:
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Also, FWIW, I get 25 mpg with my B2200 with Weber swap.

Cortnye's little b2000 gets 25mpg highway, mine gets 28mpg, but that's reading the miles the odometer says I've done as opposed to actual since I've got tiny tires

There has been plenty of guys swap to a miata tranny. Surprised the MT guys havent chimed in on this one yet!!!






-Justin

Thanks for the posts guys. Are the miata trannys a direct fit? What year miatas are compatable?

miata trans you will need to swap the bell housing and the tail housing.

Not to hijack this thread, because this could be useful to other, and I'm curious...

About going to taller tires... good that it can improve fuel economy, but will it slow down acceleration or power when passing or going uphill? (it will definitely help for cosmetic appeal and ground clearance, and improved MPG's would be a huge bonus).

As we know, there's not much selection in 14" tires these days. I've got 205/75R14 tires but just picked up some 15" rims. Not sure what size of tire to get. I'm pretty sure 215/75R15 would be a safe bet. Not sure about 225 or 235/75R15. The 4x4's could probably handle those sizes, but mine is a 2wd at stock height. However, I plan on giving my truck a bit of a lift like a Prerunner. But I was hoping to get the new tires on before the lift. Any thoughts on this?

+1 for a weber instead, it will help your mpg and help your acceleration instead of hinder it

A lot of japanese engines run at 3krpm at 100kmph (64mph) and are usually designed to be "fairly efficient" at that point.

It's not a diesel so it's not always "sucking" massive amounts of air, it's only getting what the tb allows it so I imagine the efficiency of a few hundred rpm wouldn't make that much difference? Anyone have an excellent grasp of thermal dynamics want to show the working on that one?

Get a cover for your bed and reduce your drag, that'll help plenty! I should do the same

Better yet, get a Kia

Is a cap just as good, or better? My truck came with a cap over the box that is just about the same height as the cab. I plan on leaving it on, but painting it to match the truck.

Earlier on you guys were talking about diff ratios and how a taller tire can help achieve the same effect. I just picked up some 235/75R15 tires today, partly for looks, partly for better height and ground clearance. It would be a bonus if it helps fuel economy!

Oooh... at a guess, probably better than nothing.
It makes a bigger single "plug" of low pressure but at XX speed you're making that anyway and it's designed to cover your bed (pressure coming off windshield). So at lower speeds than that a canopy is probably a better thing than not.
Did that make any sense?
Hey do us a favour and do an experiment! With vs without for a week!