Topic: Should I put a 21 spline 4.7 case behind 3.0/manual/2.28 crawl box?

[dustingro]

Posts: 3
Member since Aug '12

Crawling with Marlin




Has anybody run 21 spline 4.7 Marlin total spline gears behind a 23 spline crawl box and 3.slo? Is this just asking for trouble?

 Just swapped a stock case into my '85 pickup to put my 4.7 case into my '92 runner project. Turns out that what was supposed to be a 23 spline 4.7 case is 21 spline.

4Runner will have 2.28 crawl box and I have a pretty light foot. Just don't want to spring for new 4.7 gears.  Can I even buy a 23 spline input/21 spline output crawl box?

[dzldust]

if you already have all the parts id run it,my last 3.0 did not seem like a torque monster

[Cyberman]

Worse case scenario, you get a 23 spline adapter and a new 23 spline input gear.  You don't need a whole new gear set.

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[helipilot77]

I ran a toyota stock 21 spline in my crawl box for two years before it stripped out on me with mostly street driving. You should be fine if you buy the total spline input. It makes all the difference.

[tyes]

get the 23x23 becuase in the future you will upgrade or you'll find your self needing 23 spline...

[BigMike]

As helipilot77 mentioned, stock 21-spline parts have been tried behind a 3.0, but don't count on it to last. As for a 4.70:1 gear set, if it is an Advanced Adapters (discontinued) or Trail-Gear kit, then they will only be a marginal improvement over stock. If it is a Marlin Crawler Total-Spline gear kit, which you have, then it will last a lot longer, however, even still I personally wouldn't put a guarantee on it from eventual failure. We have seen a few 21-spline Total-Spline inputs break, but have only rarely seen our 23-spline "XD" Total-Spline inputs break (I've only seen two myself), and it's likely we've yet to have a 23-spline "Competition" Total-Spline input break, which are stronger than our XD sets.

my last 3.0 did not seem like a torque monster

Keep in mind also that the engine itself is heavier, the radiator is heavier, the flywheel and clutch are heavier, the transmission is heaver, the third members are heavier, the brake system is heavier, the exhaust is heavier, ... etc, so the drivetrain is also under a greater load due to increased mass and inertia from the 6-cylinder platform.

Will a 21-spline Total-Spline input work behind a 3.0? Yes. Will it last? Only time will tell. Would I run this setup? Only if I seriously couldn't afford purchasing a 23-spline coupler and 23-spline input from Marlin Crawler or used somewhere.

If you are a grease monkey who does his own work then this might not apply, but don't exclude the extra costs of doing the 23-spline upgrade sometime later down the road as you'll have to drop both T/case and Crawl Box, tear them both apart to replace coupler & input, and slap it all back in. At least for me I usually forget that it might be my only vehicle or that I can't afford any downtime.

Regards,
BigMike

[dustingro [OP]]

Thanks for all the input. It is a total spline 4.7 21 spline input, so might just give it a shot.

The new 4Runner is a fat b*std compared to the '85 longbed I have had this case in. Good point, BigMike!

[BigMike]

Thanks for all the input. It is a total spline 4.7 21 spline input, so might just give it a shot.

The new 4Runner is a fat b*std compared to the '85 longbed I have had this case in. Good point, BigMike!

It's not just the added bottom end torque but also the extra mass. What you could do is drop your t/case off the back of your Crawl Box and make a judgement call on how both splines (coupler & input) look. If they look pretty good with minimal wear then that could give you more confidence with re-using them. In the end however, I believe that with a 21-spline Total-Spline setup, you'll more likely to snap/shear the input than to strip out the splines in the coupler. Take this with a grain of salt and 1) drive accordingly so that your truck will last for many, many more seasons of fun , and 2) enjoy what ya got and get out there and

If you are really worried, just carry an extra stock 21-spline input gear with a used bearing pre-installed. Spray some WD-40 all over it (prevents rust) and store it in a plastic bag next to your spare tire jack.

Regards,
BigMike

[dzldust]

if 21 spline is so sub par,why sell it or even offer it?

[CrazyYota]

if 21 spline is so sub par,why sell it or even offer it?

Because all 4 cylinder toyotas are 21 spline. unless its a turbo.

[dzldust]

thought you could use 23 spline between the cases?

[dustingro [OP]]

thought you could use 23 spline between the cases?

Issue with that is I would have to buy new 23 spline 4.7 gears for the 21 spline 4.7 case i already have.
SO.... v-6 adapter plate, 23 spline input into the crawl box, 21 spline coupler, and bolt up the case I already have.
and remember how much of a pain in the arse it is to fix if it breaks every time I think a little more throttle might help! 

[BigMike]

thought you could use 23 spline between the cases?

This is correct and at no extra cost (21-spline kits are the same price as 23-spline kits) unless you've already purchased 21-spline parts. Now you are stuck with the 21-spline parts OR you must shell out more dough to get 23-spline parts.

Regards,
BigMike