# T-Jet/ JL Drop Axle Revealed



## Bill Hall (Jan 6, 2007)

Video Jimmy I'm not. So no laughin' at the old pics! The pics are of the original first hack (prototype) so they're pretty rough and not an exact reflection of recent evolutions. The idea should still come through! I'll preface this by saying that I usually have some idea where I'm going with one of these before I build one. Be it saving a severely butchered original, or changing the character of a box stock body. No collector value/mint chassis' were harmed. I like lowered properly stanced cars. My chassis box was overflowing. Every body's got one. I studied the traditional methods for lowering and was left wanting. Hoggin' out motorpits by dremeling and sanding is just too tedious for a lazy guy like me. It drops the CG but your still stuck with shopping cart fray wheels to close the air gap and complete the effect. This in turn leaves some wheel well issues as the overall tire and wheel diameter shrinks. Post shaving works OK but gets limited pretty quick at the gear plate. A decent drop but not a slam. I had seen some vague pics of chassis mod on the Yahoo T-Jet site, like I found later under Dr Synths in the HT photo album, but nobody new jack about it. I began by studying the early AFX chassis, nice ride height, tall tire profiles, and superior handling for the times. I selected a great t-jet chassis with porked rear axle holes. Step 1: With a sharp #2 blade cut out the rear pinion shaft plate up to the rear magnet housing and square out the back leaving the rear screw apron. Trim the inner rails neatly! Step 2: Make an indexing jig from the front of another junk chassis. Again cut the front pan area away and trim the rails neatly. Should look like a pickle jabber. Trim the front right up to the long wheelbase hole. Step 3: Scribe a vertical line on the rear chassis rail through the axle hole center using a small square. Overlap the jig into the rear of your chassis from the top. Pin the jig all the way through the LWB hole and the rear axle hole of your chassis and out the other side. Use some piano wire or fat axle so it's tight but will hinge. Using good light, rotate the jig until the truck axle hole aligns with your vertical scribe. Mark it. Reset the jig to overlap the other side and mark the other rail. Remove the jig and check your measurements for square! If it's skookum, drill each hole separately with a sharp drill and use every effort to stay straight. I ream both holes together with a wide flute JL long axle and some compound in my cordless drill. Go slow you want to cut and polish not melt the hole to size. The wide flute axle holds more compound and slings the compound centrifugally when spun. Check progress frequently with the axle you intend to use, and redress with compound as required. Change sides a couple of times too! Re-trim any flash that might appear after reaming. Step 4: Slip an axle and crown gear on the chassis and check clearances. Select a good bare gear plate. A good pinion hole is vital! The gearplates left rear index tab and pinion button are snifed flush with your blade. Step 5: A crown gear clearance window must be cut in the gear plate under the driven gear. I use the dremel to plunge cut a hole big enough to get my blade started. Trim right down the rail on the left. Carefully trim the left edge of the window to within 1.5 mm of the pinion hole. Careful!!!! You should end up with a neat little rectangle. Try snapping the gear plate in and trim for crown gear clearance as required. Step 6: A relief pocket must be cut on the gearplate bottom for a modified pinion assembly. For this I use a small round flat faced stone in the dremel on slow speed. Go slow at first so you don't kite off center. Plunge cut to half the gearplates thickness and finish by tilting the stone slightly around the relief perimeter to crown/cone the hole center for pinion clearance. A floating pinion is created by mounting the pinion at the shaft end. Fit the pinion with shaft into the gearplate and snap it all together with the gear clamp, so you can check the pinion and crown mesh. If it's good, mount the driven gear and leave the extra shaft for now. It makes final adjustments easier if required. Mount the armature and assemble as normal then check for gear bind and correct if required. Step 7: AFX style pick ups (stepped or ski) and springs are required. Don't waste time on the other stuff just trust me! Snife the pick up spring indexing dowels flush with your blade for proper shoe travel. Sharpen the shoe hook slightly and mash the hanger plate a skoshe for proper shoe and spring retention.... or boink disappearing springs. A little shoe tweaking may be required. A little roll on the contact patch just behind the front window shuts them right up. Gently! It doesn't take much to get it right or screw it up. Your front end setup goes in the truck hole for now. The front mount screw will need a serious shave or use a fancy no profile one. Mount the guide pin with an old wheel hub and go for a putt. Ha! Fooled ya ! The guide pin must be trimmed. I do this on a case by case basis during testing as there is no magic number here. One slice at a time until it's right. If everything is right and your cutting some smooth laps with no gear racket, go ahead and bob the remaining pinion shaft with the dremel cut off wheel. Don't make a production out of it so you don't heat the all important pinion hole. Short and sweet does the trick! As a rule of thumb this mod requires a standard AFX tire diameter, I guess about .474. I've gone lower but it can upset the front to rear chassis rake angle requiring a front tire profile change and subsequent shoe/spring adjustments. My recently posted Red GT-40 has the extreme 490's, about as far as you can go without shaving the rear magnet housing and keeping the tires under a standard body. Again, use the truck hole for testing. It provides a near level chassis setup with just a bit of forward rake. Getter' running first. The front axle holes can be moved later using the same jig if you need to go either long or short WB. It's tight up front and care must be taken not to wander when drilling new holes! Prior planning will take a lot of the aggravation out of this. Wheel well mods are a given , but generally only in height not width so be careful. Measure once,.... then again and recheck before you butcher. Hub shaving and wheel narrowing are often necessary. I have only done this mod with the 9 tooth pinion. It works well with taller tires as I only have an 8X10 dogleg test track. For hot motors and mags some venting always helps and looks cool too. So there you have the "AFXication" of the venerable T-Jet. Some might question durability, but to date hundreds of laps have been completed with no unusual effects. This mod's not for everybody but it does provide a lot of wiggle room when lowering. The beauty is that one can still post shave, plate rail delete, and bevel the rear plate end rails and driven gear if you want even more dump. Not to mention scooping out the underbody. For those who build the drop axle chassis; I can safely say if you get it right, you'll be surprised at the flat secure handling, and a smidge of improved acceleration even in stock trim. I think it's due to lightening and the loss of one bearing surface, as well as the superior characteristics of the AFX pick ups. 3/4 of the job is done with the knife and dremeling is kept to a minimum. Hallelujah.


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## 1976Cordoba (Sep 20, 2000)

Geez Bill, can ya dd a few paragrah returns to that?!  That's way too much text in one big glob for a Saturday morning! :roll:

I have to go rest my eyes now . . . thanks! :lol:

'doba


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## roadrner (Jul 21, 1999)

Man, I'm tired now. Have to go take a nap. :devil: rr


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## JordanZ870 (Nov 25, 2004)

That is a heck of alot of information, yeah, Bill? Thank you kindly for sharing it!
I hope you don't mind, but I have printed it off so I can study it and work a chassis as I read through it. It looks complete and well written to me, eh! Ok, 

Ok, off I go! I will let you know how it turns out!


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## Bill Hall (Jan 6, 2007)

*RE: Glob -O- Text*

What? I give you one simple paragraph of instructions, and the steno-pool whips out the correction fluid. :lol: 20 words a minute with 40 mistakes and the spellcheck is wincing with an ice pack on it's head. That's a good day for me! :thumbsup: Couldnt find my crayons, grandson ate'm. Where I came from we wrote with spray cans. I assumed there would be a lawyer or used car salesman that could translate my glorius run-on paragraph in one breath.  I took one look at that mess, and thought to myself, "Indent some paragraphs and fidget with grammar and punctuation, or go play slot cars?" Obviously the copy editor went racin'. Duh!  Isn't the paragraph thingie one of those gizmos in the little tool bar above? Seriously, I dozed through typing, it was after gym! Good luck Joe!


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## jph49 (Nov 20, 2003)

Thanks for the write-up, Bill. It gives me some insights for a new project. Really liked the way it made the Cheetah you did look.

Patrick


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