The AX15 5 speed is used in Toyota trucks and Jeeps. It's rugged and reasonably compact, easily handle 300 hp...Should be available in Australia ...comes in 2 and 4 wheel drive versions Rear this...https://www.novak-adapt.com/catalog/adapters/engine-to-transmission/ax15
Exactly. The downside of spending a bunch of time (and possibly money) to get the perfect oddball parts is that if and when they fail you'll be spending at least as much time and money again to find replacements - if they are rare today it will be worse a few years down the road.
Thanks, Jim; Hone is who I was thinking of. Esoteric tranny? . Was common, depended on where you looked. I've got ~8 of them sitting here, 5 in cars. I do agree on using a late model 5 or 6 sp instead. Although you can make a good argument for going either way. But the OP didn't ask about that. So I gave him a few ideas. . &, btw, that same argument holds for the rest of the driveline, incl brakes & engines & like components. . Marcus...
Knew a guy who had a '68 MG with the inline six and a four speed with electric-operated overdrive. He replaced the six with a 327 SBC and had no issues, so it must be a stout unit. Probably hard to find, but thought it was worth mentioning.
Use a Laycock De Normanville Overdrive that was common on Volvo's ,Jags, Astons, Triumphs etc These are electric, so a reverse lockout is simple. And the "mechanical" speedo drive is on the RH side of the tailshaft This is basically what gear venders did, they adapt the laycock to a TH400 and also converted one to a stand alone unit
The AX15 [and alloy case Supra] trans has a funky bearing retainer on the front so it would require a special bellhousing. @Reidy needs to retain his bellhousing which has the engine mount pads on it A better choice is the early "Iron Case" Celica/Hilux/Hiace which has a normal bearing retainer. These have been adapted to 308 Holdens and 302 Fords for years in NZ /Aus All you need is an adaptor ring on the bearing retainer and re-drill the bellhousing. The input shaft is slightly shorter, requiring a small adaptor to extend the pilot bearing. [If the Reidy goes down this path , I will give him the pilot bearing adaptor that was from a 283/Celica combo. I have this in my pile of bolts etc] We need to take note that the Reidy is in Australia.... The Holden 4 speed and Falcon rear-end is readily available there and will suit his needs. The Holden 4 speed has the shifter arms on the RH side [needed for RH drive in Australia]
Your info is helpful......The link to Novak shows the adapter to mate the AX15 to a Chevy bellhousing with the typical bolt pattern first used on 48 truck, then the 55 car and remained the same to the 80's. If he keeps the 41 housing, no transmission other than the original type will fit without some sort of adapter or reworking....
Thanks for all of the input. The 261 Chev I will be using is a 1958. It has a different pattern to the 41. The 261 chev has the bell housing. Something I find surprising, and I am not being critical here, is if I asked could I put a 1980 Toyota 2F Land Cruiser motor, which is similar in design to the 261 Chev, and the Toyota 5 speed box I would likely be told it is not HAMB appropriate. Yet it could be made to look so similar to a 261 only a few would notice. Yet the T5 appears to be accepted by some. I like the look of the Laycock De Normanville Overdrive and will do some research as we had a lot of Jags and Volvos in Australia. As for all of the other suggestions, more info is better than no info. That is what I am after. If it helps others that is a bonus. There are many ways to skin a cat and see all the options helps me pick the best way for me. If I decide to go late model 5 speed I would go a T5 as I can get one with the same bolt pattern and spline count out of a V8 Holden Commodore. Steve
If you're using a 261 Truck bellhousing ,it will have a larger bore for the SM420 trans. So you will need to machine up a simple locating/centering ring. If you're using a Car bellhousing it is the same bolt pattern as a Muncie/BW Super T10 [and same size hole] But the engine mount pads are different on the bell between car and truck. The gas guzzling Toyota 2F Land Cruiser motor, is a totally different animal to the 235/261 Chevy. The engine has a lot more length and nothing interchanges. But the early cruiser engine does have a neat 2 barrel vacuum secondary Mikuni Carb that is worth considering. Just be careful with the V8 Holden Commodore T5 , [halfway through production they switched to Ford Bolt pattern which is more common] The GM pattern is an early NWC T5 Also check the T5 for electric or mechanical speedo drive [you cant swap them without a tailhousing swap]
Are you sure about that? I've always found that the SM420 uses the same size center hole as the car transmissions. The later SM465 (1968-on) uses the larger center hole, as do later 3 speed transmissions that were installed in 68-up trucks.
I had the Laycock de Normanville in an Austin Healey when I was a kid. Great set up. As factory installed in the AH it worked in third and fourth gear. Switch off, normal four speed. Switch on third and fourth were the o/d ratio. Running in either third or fourth it “kicked down” from o/d to standard ratio with the throttle like an automatic. Great in bopping along thru traffic. Leave the trans in third or fourth (depending on speed of traffic) with the o/d engaged and toggle between the two ratios with your foot. Most of the time as a daily I just left the overdrive engaged all the time. Between the original owner (a family friend), my father, and myself we put over 150k miles on that little car, and the o/d was bulletproof with nothing but routine maintenance.
The LdN and GV overdrive has a pump in it, so it needs to have the car moving before it will build pressure, so it won't work if you try to engage it at too low of a speed. And also the way the overrunning clutch is set up, it will break if you engage it when in reverse, so it needs a positive reverse lockout of some sort. Having it only engage when the shifter is in the 3/4 position is a great way to accomplish this. That's how it worked in the Triumph I had several years ago. In my old Chevy, I have a switch on the TH400 shifter that only allows it to engage in high gear (it has a full manual valve body).
Simplest: no OD. Gear it and cam it to run down the road at highway speed comfortably. Don't expect to cruise at 1800 rpm like a late model. Consider the overall cost of all the conversions to get an OD trans versus engine wear. How much do rings and bearings cost for a 261 Convert to OD: use a trans that's readily available in your area, and will hold up to the engine your planning. Paying 5X more for a trans that's acceptable on this site being shipped from US versus using what's on your continent is crazy. TKO: look hard at all of the conversion BS required to use a stock trans and adapters. Unless you have access to a machine shop, the TKO is usually a better deal on a better trans. I can't speak on 261 to TKO specifics. Sounds like there's unique bell housing challenges. RPM in general we've all become scared of RPM in the last 20 years or so. These engines hummed down the highway for years, they did get worn. Most of these are hobby cars that get driven limited miles per year. Rebuild the engine, let them wind, insulate the cabin for noise. It'll be a long time before they need a rebuild due to limited use they get. I bet we can still freshen an engine for far less than most of the available OD trans options.
The reason most overdrives have the lock out, so that it will only work in the top two gears, is so that the torque of the engine is not multiplied as much in those gears. Most overdrive gears are somewhat “ lighter” than the lower gears in the main transmission and cannot take the torque of the engine multiplied by a factor of 3. Overdrives were designed for cruising , not all out performance. As designed by the OEM , if you go to WOT the OD will drop ,out and go to direct. Most overdrives were designed to be used only in high gear, but due to design factors , the OD could also be used in second gear, which puts almost twice the torque on the OD unit than high gear! Also, liked mentioned, most ODs don’t like reverse. Also , the longevity of the OD depends a lot on the driver and the torque of the engine in front of the OD. I took an OD from behind a Y-block and mated it with a 200 cubic inch six in a 1960 Econoline. Now that combo was bulletproof! Lol Just some thoughts on overdrives. Bones
I don't know of any overdrives that have such a lockout, for that reason. The BW overdrive can be engaged in low gear if you're going over the governed speed.
I as referring to Boatmarks post, maybe I should have said “ Some” instead of “most”. But the basis of the fact is that most/some Overdrives cannot handle WOT in low gear. They were not designed to do that. It has been forty years since I did that combo, so I am a little foggy on the actual details on it. But it think the speed at which the governor will let it work is at the upper speed of low gear ,or close. Bones
I was told by an old British mechanic back in the 70’ that engine torque was the reason the smaller engines (Spitfire or Sprite) had o/d in 3/4, while the larger Healey’s only had it in 4th. It was electrically controlled off the shift linkage that way in a Volvo I had. Just for background if you’re swapping one in.
Yeah, some of them don't like the torque they get in low gear! The BW planetary needle bearings, especially.
The is going to be a lot of measuring and some adapting to fabricate whatever you chose. The fewer number of parts that you have to fabricate will probably give you the best chance for success and reliability. With a 5 speed transmission you have the simplest path to get where you want and the fewest number of components to wear or fail. Probably the least amount of fabrication needed.
Traditional? No one will like this answer but a traditional way to do it is use 2 3 speeds, one turned around backward and coupled to the other. That gives you a few OD gears and is actually an old old trick. OK you have other options, that I probably won't throw out there. LOL
Aww, wth, Beaner, drop the other "options" on us. Don't hold back... . Inquiring minds want, no, need, to know! . Marcus...
Reidy, I have to ask, is the vehicle you're working on a dinky half-ton pickup or that two-ton monster you have in your Avatar? The GVW is going to dictate what transmissions are appropriate to use.
The short answer is it is the body work of my avatar on a 115 inch chassis with a 261 engine. The long answer is contained here https://www.jalopyjournal.com/forum...ruck-41-chev-long-read.1195381/#post-13631698 If you read the long answer I am solving the transmission question. I solved the I beam question by using an International truck I beam, the 12 inch backing plates and 12" 6 stud hubs from a caravan. I am staying reasonably on track to the long answer. Steve
That is incorrect. Mine was in fact in a final generation (BJ7-8) Austin Healey 3000. Although technically an option, all the 3000’s of that generation shipped to the states had the o/d, and it was third and fourth gear.
A thought came to mind, and I think many here have the knowledge to answer - would a period solution be a two speed rear axle? I know nothing about them other than my father talking about them. Would this be a option rather than o/d trans?
The two speed rear axles used in larger trucks give you an extra low gear...not overdrive...so no, it's not what you want.
I know I have pushed for the T5 transmission for your set up, but I just happened to remember a few things. Eons ago I had a Ford single axle dump truck, International Backhoe, and a heavy trailer to haul it with. It had a 300 cu in 6 cylinder and a 4 speed. I swapped it out for a 5 speed and it was one good decision. The 6 cyl did pretty well pulling all that weight. As I remember now, the problem was more about trying to stop......and it didn't have power steering. Anyway, the trans made a lot of difference with that 6 cyl motor. Since you are doing this for a large truck, it seems applicable to your question. Also, I went to a swap meet earlier this year and met a guy who was selling 5 speed conversions and he was working on a set-up which would provide 10 speeds for the T5. Don't remember the details, but he was a very nice older gentleman. If interested, you should be able to contact him here: John Baker 606 348 8533 [email protected] He's in Monticello Ky Here is what I put a 5 speed in years ago, but it was before they made the T5. It was a heavy truck transmission. I'm thinkin the truck was a mid 60s Ford. The backhoes wheels used to raise into the air when being loaded on the trailer. It was a lot to ask of the little 300 six engine. My pole barn now sits just about where the truck is in this picture.
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