TR overall gear ratios for euro, CH, and US versions

Since I had made an excel file to calculate the overall drive ratios for each gear of the various versions of 308QV, I thought I could easily just change the various teeth numbers and get similar results for euro, CH, and US version TRs. I was wrong . However, I learned a lot about the different TR versions and how each version had changed gear-wise over the years:

1. I was surprised to find that 1984 to about 1990 euro TR and 1985 to somewhere in mid-1988 US TR have identical gear ratios (these are the values shown in the TR WSM on page E14, but they mangled their own “final reduction ratio” calculation a little).

2. Somewhere circa 1990, the euro TR had a very slight change to the 1st and 2nd gear sets and split into two separate types with different transfer gears: “without catalyst” that retained the 27/29 transfer gears, and the “with catalyst” (I think this might be the “CAT” version mentioned in the TR SPC) with 26/27 transfer gears (making it very much like the early CH version).

3. The CH version is a different beast, but it follows the same trend as 328 CH where, by using a less reducing transfer gear set of 26/27, every gear of the 1985-1987 CH version is taller than the 1984-90 euro version (where I’d guess that Ferrari assumed that you be in one gear lower than normal in hilly/tight terrain so making that lower gear have a taller gear ratio helps limit engine over-revving and noise). For the 1988 CH TR, the corresponding OM indicates that they changed the diff ratio to a lower 17/61 value which lowers all of the gear ratios (but I am a little suspicious if this was a typo as the OM table of the final drive ratios for 1988 CH version TR was not changed from the 1985-87 CH version TR OMs).

4. On the US TR, somewhere in Model Year 1988, they changed the transfer gear set from 27/29 to 27/30 (the 480/87 TR OM shows that 1988 Model Year US version TR can have either 27/29 transfer gears or 27/30 transfer gears). My guess would be this roughly corresponded to the change from single-bolt wheels to the 5-lugbolt wheels, but the SN switchovers for both changes in the TR SPC don’t match up exactly (5-lug wheels starting at SN 75997 and the transfer gear change starting at SN 76474).

Maybe what surprises me most is that I can’t recall a single time that these differences in gear ratios between the TR versions, or within the same TR version, has ever come up here for discussion. Maybe the greater power and torque of the TR engine just makes it a non-issue. Here are the results for each version TR:

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You're giving me homework! I don't have any TR CH OM later than the one for the 1988 year. I've got three euro 512TR OMs (dated 91, 92, and 93, but they aren't clear about what model years they apply to) and three US 512TR OMs (dated 91 for 92 MY, 92 for 93 MY, and 93 for for 94 MY). I've got no CH 512TR OMs -- so please post any 512TR CH OM gear/gear ratio/# of teeth information that you have.

 

Greg -- Even though your CH car came with the 790/93 OM, it does not mean that the 790/93 OM is for a CH version 512TR, and Ferrari is pretty good about labeling the OMs when they are not for a standard (euro) version. I'm 99.9% sure that the 790/93 OM is for a euro 512TR as the pictures of the transfer (idle) gears at Maranello Classic Parts show that the CH 512TR transfer gears are 26/27 (which is identical to all the other CH version models) and the euro 512TR transfer gears are 27/29. The 512TR SPC also shows that there are no different CH (nor US) gear sets and no different ring and pinion for a CH (nor US) 512TR. Consequently, I'll do the CH version 512TR table with:

transfer gears = 26/27
gear sets = same as euro
ring & pinion = same as euro

And the US version seems to be:

transfer gears 27/30
gear sets = same as euro
ring & pinion = same as euro

but I'll give everything one more careful look, and then post the euro/CH/US 512TR table in a day or two.

Have you actually decoded your VIN at red-headed.com to confirm that it is a CH version? (Sometimes a euro version that gets sold into Switzerland and then gets sold to the US can get the moniker of being a "Swiss" car when it really isn't.)

 

Agree that it's a CH version if the 8th digit of the VIN stamped on the car is "S" (although you haven't stated that directly). The Swiss Dealer adding a stick-on label to a euro manual is something they would do if there was no CH manual available (and that may be the case as the OM file set from Ferrari doesn't include a CH 512TR OM). Also, sometimes Ferrari just added a small single/few page insert to an older/different OM and maybe that got lost (my 1991 US TR came with a 1989 US TR OM with an insert titled "Changes for M.Y. 1991). The different versions for the OM (from that era) are usually indicated on the title page of the OM like these examples for the TR (the "blank" one on the left is a euro version):

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But no matter -- I think the 512TR transfer gear photos from Maranello Classic Parts and the 512TR SPC information showing that no special CH or US gear sets nor different CH or US diff gears is pretty strong evidence, and will proceed on that basis. Although speedometers and tachometers aren't super-precise, your CH 512TR should have a low RPM to go 60mph vs a euro 512TR and especially lower vs a US 512TR.

 

No, first blush is that the Boxers are more like the later US TR because the Boxer transfer gear ratio is 27/30. My guess would be that the goal on the early TRs was maximum top speed (and 4-valve TR had a little more power) so they went to 27/29 on the transfer gears on the early euro TR and the early US TR. There are some gear differences, too, between BB512 and BB512i, with 1st gear on a BBi being lower than a BB, and 2nd gear on a BBi being a small bit lower than a BB (3, 4, and 5 seem the same, but they completely butchered the overall reverse ratio entry for a BB512i in the OM as being an impossible 1:0.418) . Let me get the 512TR stuff done and then I'll have a closer look at the Boxers, but let me add that it's often (on all models) like the F engineers calculator was sometimes broken, or they mangled a hand calculation, or sometimes things got mis-transcibed as often they'll give the exact number of teeth yet their own corresponding calculation for that tooth ratio is off in the 2nd or 3rd decimal place by a small amount greater than just a rounding error.

 

No, what you have (790/93) is what we typically call the "Owners Manual" here even though Ferrari changed the name (and the form factor) to "Technical Manual" on the 512TR.

I don't know 928, but it sounds like they made the trade-off that many auto manufacturers make where the top gear is very tall to get better MPG in that top gear, but the engine really doesn't have enough power to get to redline in that top gear -- if it could, you'd be going 200 mph in your 928 at the ~6K RPM engine redline . Since Porsche's claimed top speed for the 928 is more like 140 mph, it probably does that in 4th gear. Many modern Corvettes are like this, too, where the upper gears are so tall that the maximum speed is achieved in 1 or even 2 gears below the top gear.

 

See this thread where I posted the 512TR overall drive ratios with those different transfer gears (I stated the reasons I think they made those transfer gears changes there):

https://www.ferrarichat.com/forum/threads/512tr-overall-gear-ratios-for-euro-ch-and-us-versions.672830/

 

The gear ratio information for the BB512 and BBi512 are in this thread:

https://www.ferrarichat.com/forum/threads/boxer-bb512-bbi512-overall-gear-ratios.673140