J160 gearbox conversion guide
Using various components supplied from our business it’s quite straightforward to convert a vehicle with a 4age / 7A engine to use a modern 6-speed J160 transmission.
This is a significant upgrade over the original gearbox and is an excellent conversion overall. This is due to J160 gearboxes featuring a very nice range of gear ratios, modern / optimised internal design, taller final drive for lower highway RPM, having a strength comparable to that of the old Supra Style / W5x gearboxes and due to being newer they are significantly less prone to being worn. Without the shifters and dry the J160 is only 9.5kg (40kg total) heavier than the T50 it replaces.
Additional information
NOTE: This is one of two articles that features information on performing a J160 conversion, the other also features technical, modification and other information. It can be found here:
– Additional J160 conversion and modification information
In due time these two articles will be combined together for simplicity. It’s highly suggested to read both articles.
Potential Parts Checklist
Engine to Gearbox adapter: There are two different models / variations of this J160 gearbox and we offer individual adapters to for each to bolt to a A-series engine
Gearbox adapter kit: 4AGE / 7A to J160-G (1GFE)
Gearbox adapter kit: 4AGE / 7A to J160-S (3sge Beams)
Gear stick relocation kit: The OEM design allows for two different possible locations of the original gearstick. Unfortunately both of them are still quite far rearward. Our Relocation kit moves this another 110mm further forward from the front position to allow it to fit out of the original shifter hole of cars such an AE86.
J160 gearbox- Gear shifter relocation kit
Speedo drive: The J160 normally uses an electronic speed sensor. Conveniently a mechanical speedo drive can readily be fitted where required. Pending on the amount of teeth on the gear the drive from a W5x / “Supra” gearbox will fit right into place.
J160 gearbox- mechanical speedo drive kit
Gearbox to body mount / crossmember:
– Engine crossmember spacers: For some car models it maybe required to use either lowered rubber engine mounts or Engine crossmember to body spacers to allow enough clearance for the bellhousing part of the new gearbox to clear the body.
AE86 / AE71 / KE70- Engine Crossmember Spacers
Tailshaft: The output spline between a T50 and a J160 is different, however the J160 and W5x / “Supra” gearboxes share both input and output splines. Pending the length a tailshaft from a W5x gear is likey to fit right into place. For others it’s not expensive to have the existing tailshaft modified. Another option is to fit the tailshaft from a different model that is compatible. A RA40 Celica is reported to have the correct length and spline type to suit and bolt to the rear of an AE86 tailshaft.
Clutch line: A new custom clutch line will likely need to be made. This is a cheap and easy process with many businesses offering the service. This custom line can be made to join the existing metal line on the body or be made to run all the way to the clutch master cylinder. For people using the J160-G (1GFE) a “Banjo” type fitting is suggested for the slave cylinder connection. Australian customers can use this website to easily find the businesses closest to them offering the service. NOTE: The thread size of the J160 Clutch slave cylinders, the metal clutch lines and clutch master fittings as used on Toyota’s all use an M10 with a 1mm pitch.
Installation notes: Car body clearance
During the development of our 4a to J160-G gearbox adapter a J160 was fitted into the SQ-Engineering AE86, this was done without any modifications to the body and using the same parts as what we offer for sale. The following was used / undertaken by us to make this possible. Most of these are likely to apply to other car models as well
– Gear shifter relocation kit: One of our relocation kits was fitted to allow the shifter assembly and gearstick to fit out of the original hole. This makes it also compatible with the original center console and rubber gear stick boot.
– Engine crossmember spacers: The top-middle of the bellhousing would likely touch or be just off touching the body, to give some extra clearance spacers were fitted between the engine crossmember and the sub-frame of the car body. These are only 10mm thick and don’t require different bolts nor any different parts in the steering. We offer these for sale.
– J160 Gearbox type: We used the J160-G model from originally behind the 1GFE engine. The other type of J160 (3S Beams) has the top of the bellhousing section is physically a little taller, this may cause it to be just off being able to clear.
– Gearbox housing: Some of the external ribs were ground down a little, this can be seen pictured below. This is a 5 minute job with a hand grinder and a flapper wheel with no accuracy required. This modification does not compromise the structure all.
Highlighted in red is the ribs that have been modified. The left side of the gearbox (next to the Toyota logo) was for clearance directly off the tunnel, however the right side was for fuel line clearance. The highlighted section on the top of the bellhousing is where it comes the closest to touching the body of an AE86, as pictured the ribs should be completely removed in this section.
While not a modification we had to undertake if more clearance is required another way to go about it is to directly cut a whole section out and weld a panel in it’s place. Photo courtesy of Simon.M.
