buzzboy HalfDork
11/23/19 10:06 p.m.

Spitballing my 2020 project plans. I'm working on a 3000lbs car, street and maybe a track day, hopefully 120-150whp and 200-250ft*lbs, manual transmission. I'm not into building an adapter plate for the planned VW TDI so I've been researching pre-built adapters. All of these would use the donor's flywheel, PP and clutch. There are plenty of good bolt pattern options but I'm thinking gearing, quality/speed of shifting and availability of quality used transmissions.

Two things I want to keep in mind:
My car has 3.07 gears and not too many other options in the US, except my spare 2.63LSD(in case I go cummins?).

I like a slightly longer, notchier shift, like a short shift kit and a long handle.

So the bellhousing patterns I saw available:

Nissan L/KA/Z transmissions

Jeep AX15 or NSG370

Toyota R151 or W56

Chevy Smallblock 2piece or 1piece rear main(too many options to list)

Dodge Smallblock (not sure what all the options would be)

Ford T5 or M5ODR2

Of all those choices I've driven a Nissan Z(the truck engine), Nissan KA, AX15, W56 and Mustang 4.0 T5. A few of those are truck transmissions that don't belong in a sporty car. I liked the shift feel of the  KA trans in the 240SX but I don't know what else was going on in there as far as gear ratios and weight and power and.... I also really liked the Mustang T5 for it's shift feel, probably even more so than the KA transmission.

ProDarwin UltimaDork
11/23/19 10:13 p.m.

Whats a dyno look like for a 120-150whp TDI motor?  Is that at like 3000rpm?

Daylan C
Daylan C PowerDork
11/23/19 10:15 p.m.

In reply to buzzboy :

I'm thinking ford T5 is probably going to be your most readily available option. You have all your Mustang transmissions and I think v6 4th gen f body t5s were Ford pattern cases as well.

ShawnG PowerDork
11/23/19 10:16 p.m.

T5. Cheap, gettable anywhere and easy to rebuild.

After that, the M5OD.


pres589 (djronnebaum)
pres589 (djronnebaum) PowerDork
11/23/19 10:22 p.m.

T5 due to the rear end ratio / first gear combination not being a crawler setup. 

slowbird Dork
11/23/19 10:22 p.m.

M5OD is also available in Super Coupe Thunderbirds, albeit slightly different from the truck version. Supposedly stronger, from what I recall. I need to get one to swap into my Cougar someday.

SkinnyG UltraDork
11/23/19 10:37 p.m.

I -believe- the gear ratios are the same between the Hardbody and the 240SX. 

pres589 (djronnebaum)
pres589 (djronnebaum) PowerDork
11/23/19 10:40 p.m.

I thought the M50D in the SuperCoupe had a taller 1st gear vs. the truck boxes which is where the added strength comes from.  Same box, slightly different gearing, that's it.

slowbird Dork
11/23/19 10:44 p.m.

In reply to pres589 (djronnebaum) :

Could be, I honestly would have to look it up again. I remember there being some reason to look for the SC one specifically instead of just getting the more common truck version.

Curtis UltimaDork
11/24/19 12:58 a.m.

The M5OD has a nice first ratio to match the low-ish hp and the gears you have.  The only problem I have with it is that it looks like a nice trans, seems like a nice trans, and can take a fair amount of torque, but fast shifts are not what I would call its strong point.  It shifts more like an SM465.  Yes, notchy, but definitely slow.  Certainly not a performance choice.  I suppose you could take out every other spline on the dogs, faceplate it, or dog box it, but not likely to fit that into a challenge budget.

The T5 is so common you should be able to find a good ratio choice and not spend a fortune.  At your power levels, they will last forever.

Have you thought about an AX5?  It was the wimpy, bastard brother to the AX15.  Came in zillions of Jeeps from mid 80s-2000s and were known for sucking as an offroad transmission when you gave it the torque feedback from a low-range transfer case.  For that reason, Jeepy people often sell them for pennies.  Find one from a XJ, YJ or TJ on a jeep-ish forum and you can likely snag it cheap.

Hit up some Ford Ranger resources.  Lots of TDI swaps in Rangers.  They have resources on T5, NV3550, and other transmissions.

Knurled. MegaDork
11/24/19 5:54 a.m.

Chevy V8 T5 because they're less valuable than Ford V8 T5s, and they have the closest gear spread, which you will need for your narrow powerband.  Also, since Diesels don't accelerate well but they load down well, the engine will appreciate the tall first gear.

Actually the Autogear "M23" transmissions would probably be the awesomest, because they are NEW, and they have closer ratios than any T5 fould dream of.  But even as cheap as they are they'd blow budget.  (I assume "2020 plans" mean "GRM challenge plans" here)


Doing anything with a Chevy transmission pattern will give you room to grow as Chevy basically used the same pattern for decades, and every grassrootsable racing transmission under the sun is made for the Chevy pattern.  The Jerico pattern is the Chevy pattern with a couple more bolts added.

buzzboy HalfDork
11/24/19 6:52 p.m.
ProDarwin said:

Whats a dyno look like for a 120-150whp TDI motor?  Is that at like 3000rpm?

250ft*lbs at 2300-2500 and 150hp at 4000

pres589 said:

T5 due to the rear end ratio / first gear combination not being a crawler setup. 

That's something I think about a lot in a street car. My summer DD has a final crawl ratio of 12.3 and my winter DD has 9.7. A  Mustang T5 would give this car either an 11.5 or a 10.2 depending on generation of transmission. Both right in the meat of what I'm used to driving. The V8 Camaro T5 as mentioned by Knurled would come in at 9.0.

Knurled said:

I assume "2020 plans" mean "GRM challenge plans" here

Actually, no. This is my old Lemon that blew up in 2016 and I want to bring it back to life. It's slow and stupid so I'm "bending" the Lemons budget and I'm not sure it'll ever race again but I am a cheap bastard and I want to keep it in the Lemons/GRM vein of thinking. I've got 5 months until I see the car again and I want to have all my research ready so I can get some work done on it next year.


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