Thinking about a manual transmission swap for my 99

[WrenchTech]

I’m very happy with the automatic, but I am confronted with the problem of wanting to flat tow my 4runner behind my RV. I don’t want the extra weight and inconvenience of a trailer and I don’t want to be taking the rear driveshaft on and off. So I am thinking about a manual transmission swap. That alone would not solve my problem and so I am also considering installing the earlier style gear type transfer case. With that set up I would have a vehicle that could be flat towed. When most people talk about doing a manual swap on these vehicles they are planning to do an OEM style swap with the correct chain drive transfer case. I cannot do that because those t-cases are not towable because they have a lubrication pump that requires the input shaft to be turning to function (I don’t know this for a fact but this is what I’ve been told). I am almost 100% certain that’s the RF1A gear type transfer case has no such pump and is simply lubricated by the good old fashion oil bath and splash method. I already have most of what is needed. An early style (short input) R150F transmission, an RF1A transfer case with a 23 spline input, a 3VZE bellhousing, an Aisin clutch kit for a 3VZE, a new flywheel for a 3VZE. I have a clutch and brake pedal assembly out of a first gen 4runnerBut don’t know if that will work.

I know that I am going to have to get an adapter to mate the transfer case with the transmission and I’m also considering whether I would be better off with a 5VZFE bellhousing and a long input transmission. In either case I’m figuring I will have to do something custom for the crossmember (or at least the trans mount) and the driveshaft lengths.

I am also considering the possibility that I might be better off with a manual ECU. I have heard that the automatic ECU doesn’t function properly with a manual swap.

 

[WrenchTech]

It just dawned on me. The gear type transfer case I’m talking about has a passenger side drop for the front driveshaft and my third GEN 4runner has a driver side drop.

 

[WrenchTech]

Well it looks like there’s no easy solution to my problem. I’ve heard there are some driveshaft disconnect devices. So I’ll look into that. Any suggestions would be welcome. I could also do a full float rear axle with selectable locking hubs.

 

[WrenchTech]

So I pondered a couple other possible solutions. One is building a hybrid R150/AX15 transmission to mate with a flipped Dana 300 transfer case. That would get me the driver side drop that I want and The ability to flat tow the vehicle without burning up the drivetrain. While I was at it, I might as well throw a NP 231 reduction box in between them to get some crawling gears. Dana 300 In Toyota w/o Adapters - Hybrid R150/AX15 Tranny | Pirate 4x4

The transmission and transfer case swap is well-documented. The folks over at front range off-road fabrication had that set up on a 1996 4runner that was the subject of a featured article in Four Wheeler magazine. This 1996 Toyota 4Runner Proves IFS Doesn’t Have to Be Weak

Another option would be to get a full floater Land Cruiser rear axle. Narrowing it down by 3 inches on the passenger side would center the differential and give it the same track width as the 4runner axle. Then with some custom axle shafts I could throw some Aisin selectable hubs on there so I could unlock it for towing. And I would get a 9 inch electric locking differential and factory rear disc brakes as part of the bargain.

 

[Bad Luck]

So I pondered a couple other possible solutions. One is building a hybrid R150/AX15 transmission to mate with a flipped Dana 300 transfer case. That would get me the driver side drop that I want and The ability to flat tow the vehicle without burning up the drivetrain. While I was at it, I might as well throw a NP 231 reduction box in between them to get some crawling gears. Dana 300 In Toyota w/o Adapters - Hybrid R150/AX15 Tranny | Pirate 4x4

The transmission and transfer case swap is well-documented. The folks over at front range off-road fabrication had that set up on a 1996 4runner that was the subject of a featured article in Four Wheeler magazine. This 1996 Toyota 4Runner Proves IFS Doesn’t Have to Be Weak

Another option would be to get a full floater Land Cruiser rear axle. Narrowing it down by 3 inches on the passenger side would center the differential and give it the same track width as the 4runner axle. Then with some custom axle shafts I could throw some Aisin selectable hubs on there so I could unlock it for towing. And I would get a 9 inch electric locking differential and factory rear disc brakes as part of the bargain.

Have you considered twin sticking your j shift transfer case? That would allow for a true neutral in the transfer case for flat towing. TWIN STICK SHIFTER TOYOTA TRANSFER TCASE CASE J DUAL MARLIN

 

[Team_Jake]

You should contact NorthWest Fab. They are currently developing a crawl box specific to Toyota chain drive cases, with a front/back split housing that can be customized to fit any chain drive Toyota tranny (including the old R150F) to many different transfer cases (gear drive case, chain drive case, atlas, NP205, & Dana 300).

 

[swapped_mini]

According to Marlin the RF1A cases should not be flat towed either. A twin stick wouldn't fix this as the output shaft still turns when it is in neutral and the input has to turn for proper oiling.

Whether you have an early or late R150 You want to use a 3.4 flywheel and clutch because they are stronger and the 3.0 clutch may slip. With short input shaft run a 3.0 clutch fork and throwout bearing. You would need a 3.4 throwout bearing and fork with the long input shaft. The 3.4 throwout is physically longer than the 3.0 bearing and it won't fit within the short input bellhousing. The difference would depend on where you want your shifter to come through the floor, I believe they would be in different spots. All 3.4 crankshafts are machined for a pilot bearing and Toyota has used the same one since the 70's in pickups and 4runners which makes that part easy. I just put one in a 3.4 that came out of an auto 4runner yesterday actually.

The manual swap "should" work with your computer but would always have a check engine light. There are differences with computers though and not all years are compatible. I think the major differences are the two different types of MAF's (98 is old, 99 is new?), narrow and wideband O2 sensors (I think this changed in 2000?), and 2004 Tacoma's were drive by wire. There may have been differences in years with 4runner and Tacoma on when Toyota switched stuff too, I can't remember. So if you get a manual computer make sure it is compatible. Mike at Off Road Solutions has all that info, he helped me but I was also buying lots of stuff from him. He might help you out though if you call him.

I think the easiest option would be just a driveline disconnect behind your auto trans.

A cooler option would be to get an Atlas transfer case for whichever trans you go with, I believe they have a true neutral that allows flat towing and/or a driveline disconnect can be incorporated into the case. This also allows for front wheel drive. A twin stick is great for a front locker too. I think they will build you just about anything you want, I would give them a call.

A full floater would be badass though too. I have the brakes to do this to my mini truck, just need to save my money for the expensive parts. :moping:

Toyota Pickup Brake Upgrade | Toyota Parking Brake Kit

 

[WrenchTech]

Thanks for all the good information. RF1A doesn't have an oil pump, but I can see where it might not get lubricated properly if only the output side is turning. A ready solution might be to do a full-floater conversion on the rear axle with selectable hubs, but that is a pricy alternative, and it widens the rear track width by 3" (which may not be a deal breaker for someone else, but is not what I am looking for).

By the way, I flat towed an '82 Toyota 4x4 manual trans/RF1A pickup from Chicago to San Jose, California several decades ago (appx 1800 miles) without any noticeable problem.

 

[WrenchTech]

I was just reading through your post again lots of good information.One thought I had though is that you could probably flat tow a manual transmission third GEN 4runner if you left the transfer case engaged in 2-high and the transmission in neutral. If I recall correctly, the chain drive transfer case has a lubrication pump that only operates if the input side is turning. If the transfer case is in neutral only the output side will turn as the vehicle is going down the road and so the pump will not operate. Now the question is can the R150 transmission go down the road in neutral without having a lubrication problem? The same would apply to a two transfer case setup with an RF1A transfer case in the middle. As long as the middle transfer case was engaged, as it was being turned by the rear transfer case, it would be properly lubricated. The only thing I don’t like about all this is that when you’re flat towing the vehicle, you’re turning all those nice gearboxes putting unnecessary wear on them. I really wouldn’t be towing it that much though so maybe it’s nothing to worry about.

Some kind of driveshaft disconnect or full floater kit with selectable hubs on the rear axle would be a great option, but it wouldn’t be cheap. I looked at Front Range Off-Road Fabrication’s website recently and noticed that the Full floater kit is a little over $2000 if you order the package with all the bits and pieces. It also makes your axle 3 inches wider overall, and if you add the D rotor brake package I think you gain 3 inches per side, or 6 inches overall. A lot of people will be happy with the additional width. I could stand to gain of 3 inches overall, but probably not 6 inches.

By the way when front range off road built there third GEN 4runner, They pulled out the Toyota transfer cases and went with a New Process planetary for the center section and a Dana 300 for the transfer case. I believe all that stuff flat tows with no problem.

According to Marlin the RF1A cases should not be flat towed either. A twin stick wouldn't fix this as the output shaft still turns when it is in neutral and the input has to turn for proper oiling.

Whether you have an early or late R150 You want to use a 3.4 flywheel and clutch because they are stronger and the 3.0 clutch may slip. With short input shaft run a 3.0 clutch fork and throwout bearing. You would need a 3.4 throwout bearing and fork with the long input shaft. The 3.4 throwout is physically longer than the 3.0 bearing and it won't fit within the short input bellhousing. The difference would depend on where you want your shifter to come through the floor, I believe they would be in different spots. All 3.4 crankshafts are machined for a pilot bearing and Toyota has used the same one since the 70's in pickups and 4runners which makes that part easy. I just put one in a 3.4 that came out of an auto 4runner yesterday actually.

The manual swap "should" work with your computer but would always have a check engine light. There are differences with computers though and not all years are compatible. I think the major differences are the two different types of MAF's (98 is old, 99 is new?), narrow and wideband O2 sensors (I think this changed in 2000?), and 2004 Tacoma's were drive by wire. There may have been differences in years with 4runner and Tacoma on when Toyota switched stuff too, I can't remember. So if you get a manual computer make sure it is compatible. Mike at Off Road Solutions has all that info, he helped me but I was also buying lots of stuff from him. He might help you out though if you call him.

I think the easiest option would be just a driveline disconnect behind your auto trans.

A cooler option would be to get an Atlas transfer case for whichever trans you go with, I believe they have a true neutral that allows flat towing and/or a driveline disconnect can be incorporated into the case. This also allows for front wheel drive. A twin stick is great for a front locker too. I think they will build you just about anything you want, I would give them a call.

A full floater would be badass though too. I have the brakes to do this to my mini truck, just need to save my money for the expensive parts. :moping:

Toyota Pickup Brake Upgrade | Toyota Parking Brake Kit

 

[WrenchTech]

According to Marlin the RF1A cases should not be flat towed either. A twin stick wouldn't fix this as the output shaft still turns when it is in neutral and the input has to turn for proper oiling...

...A full floater would be badass though too. I have the brakes to do this to my mini truck, just need to save my money for the expensive parts. :moping:

Toyota Pickup Brake Upgrade | Toyota Parking Brake Kit

I have been admiring the products that Front Range produces for as long as I can remember.

I took a big step forward in my project yesterday when I acquired a five speed manual transmission, transfer case, clutch pedal, master and slave cylinders, manual ECU, drive shafts, crossmember, shifter boot, and center console trim sourced from a 2000 4runner.