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Discussion Starter #1 (Edited)
The idea of the tall top gear is not a new one. Indeed, most VW's in time have had a top gear that goes beyond direct one to one (1:1) drive to the wheels - that is, for every turn of the engine the gearbox turns the final drive once. These higher top gears are known as overdrive ratios.

The essence of the gearbox and final drive is torque multiplication. An engine's power alone is insufficient, even when motion resistent forces are overcome, to maintain a vehicle's momentum without the multiplying effect of the crown wheel and pinion in the differential of around 4:1 - thus, four times the engine's power reaches the wheels with direct top gear drive.



In 1981 VW launched the Formel E versions of the Mk2 Polo, Mk1 Golf and Jetta. These models featured a very high compression version of the 50bhp 1093cc Polo engine. In addition to sporting various spoilers these models also featured a 3+E economy gearbox. The idea moved on with the adoption of 4+E gearing across the wider 1980's VW range, including a Formel E version of the Passat - this was the model that famously switched itself off at traffic lights - the idea resurfaced in the 1990's with the Golf Ecomatic.

As 5-speed gearboxes became common place, VW's 4+E marketing strategy fell away on paper, leaving the nuts and bolts intact. The economy gearbox lived on as a 5-speed.

Naturally, VW also built their GTI's with sporty close ratio gearing. That is precisely what some of us have in our T4 panel vans and pick-ups - close ratio transaxles, which are great for pulling away around town but they do nothing for relaxed highway cruising and fuel economy - Caravelles have the economy touring gearboxes.

High power engines need less multiplying effect from their gearboxes for cruising, but they still need to get their host vehicles moving. That's why we have first, second and third gears. Fourth gear can be an overdrive gear in some instances - hence, the most powerful diesel T4 is the most economical.

Finding Fifth Gear - 02 Family Connections

The gearbox fitted to the majority of the T4 range including the TDI (the 88bhp blue I) is the O2B and it's Syncro cousin - the O2D.

These are the versions dealt with in this article, not the...

... O2G gearbox fitted to the 102bhp TDI (including the TDI Syncro) and the 150bhp TDI, for which replacement parts are not so readily available as the critical parts are unique to this gearbox.

The 02B Gearbox is a beefed up 5-speed gearbox derived from the all new cable operated 02A gearbox design, first found in the '89 Corrado, '88 Passat and Mk2 Golf G60. From here on, the O2A gearbox shall be refered to as the "Golf" gearbox, even though it is more abundant in the transverse engined MK3 Passat (should there be any left after the T3 boys have hoisted their TDI engines) and Corrado.

Gear selection in the Transporter is relayed by heavy duty rods rather than cables and the final drive casings are enlarged to house a bigger - and stronger - crown wheel and pinion.

An O2C version was fitted to the all wheel drive Golf Rallye. The T4 Syncro's initial launch in August 1992 saw the introduction of the 02D gearbox, a development of the strengthened 02B with an additional angle housing for the drive to the rear wheels.

Gearbox Links (Golf MK2 to T5)

  • The 02A gearbox was used across the VW Group throughout the 1990's in the Mk3 Passat and Corrado range and 16V, VR6 and TDI MK3 Golf
  • The O2A grew into the O2J for the Audi A3; MK4 Golf / Bora; Seat Leon / Toledo; Skoda Octavia clan
  • The O2J gearbox can be found in the larger engined versions of the MK4 Golf family - the 1.8 20v, 1.8T, 2.0, V5 (10 valve model) and TDI's (non PD versions)
  • The O2J evolved into the O2S 6-speeder that is found in the MK5 Golf family - and also found in the Caddy
  • The O2R gearbox is fitted to high torque versions of the Polo / Seat Ibiza / Skoda Fabia models
  • The 02Z 5-speed cable operated gearbox is fitted to 4-cylinder T5 Transporters
  • For Syncro fans - The 5-speed O2Q and 6-speed O2M grew from the 02C for high power 1.8T, V5 (20 valve model), V6 4Motion and TDI PD models across the VW Group, and is compatable with the 4 Motion Haldex clutch. (The MK4/5 O2Q angle drive can be retrofitted to the O2C MK3 "Golf" Syncro gearbox for a Syncro to Haldex conversion - the 6-speed O2M does not lend itself for this conversion)
In 2000 VW announced that 6-speed gearboxes could be ordered across the model ranges. Gearboxes were grouped into one of three catagories; MQ200, MQ250 and MQ350 depending on how much torque they could handle.

Commonality

  • the 5-speed O2A, O2B, O2J 02R and 02Z 2wd gearboxes share common internal componentry although there are external detail differences
  • they live in VW's MQ250 group - i.e they are designed to handle upto 250Nm of engine torque (thus the 02G TDI gearbox lives in the MQ350 group
  • the O2A, O2J and O2R gearboxes are interchangable in the cars with relative ease
Additional Gearboxes (that we need not concern ourselves with)

  • The smaller 1.4, 1.6 litre and SDI "MK4" models originally had the O2K rod change gearbox - a development of the original 020 MK1 Golf 5-speed gearbox that was fitted to the MK2 and MK3 Golfs up to the GTI 8v and Seat's 1.6, 1.8, 2.0 and TDI MK2 Ibiza, Cordoba and MK1 Toledo. Beware though as it lived on in the 1.4 / 1.6 16v Leons and Octavias...
  • The O2T gearbox family is a MQ200 lightweight gearbox built in either 5-speed or 6-speed form as fitted to Lupo and Polo derived models and later versions of the lesser Golfs and their ilk
  • The 6-speed 02N gearbox fitted to 2001 on Sharan
  • The OA4 gearboxes as fitted to Mk5 Golf and OA5 6-speed T5 gearbox
  • any "in-line" Audi gearboxes
and, of course, the 02G TDI gearbox.


"Overdrive" Gear Sets

Of all the gearboxes, these are the only ones that match or better T4 Caravelle boxes from the following models:


Late MK2 (1G) Golf G60 / G60 Syncro / Rallye


02A / 02C (Syncro) Gearbox Codes

  • CBA, CBB - 30:39 = 0.769 as per T4a CPV
  • AYC, AYN, AWP, AYO - 34:45 = 0.756 as per T4a AYE, AYF, CCX, CCY, CHR, CHS, CRM, CRN
MK3 (1H) Golf


02A Gearbox Codes

  • ASD - 33:46 = 0.717
  • CYP (from 1996) - 29:39 = 0.744 as per TDI
02C (Syncro) Gearbox Codes
  • CGL, CGM - 30:39 = 0.769
  • CCT - 33:46 = 0.717
Corrado (Type 50)...



... and MK3 Passat (Type 31 1988-1993), (3A facelift 1994-1998)






02A Gearbox Codes
  • CBA, CGP - 30:39 = 0.769
  • AYM, AYN , AYP, AYY - 34:45 = 0.756
  • CAT - 33:46 = 0.717
02C (Syncro) Gearbox Codes
  • AWR, AYR - 34:45 = 0.756
  • AME, CBC, CDG, CDH - 30:39 = 0.769
MK4 (1J) Golf


MK1 Audi A3 (8L)


MK1 Seat Leon (1M) / MK2 Seat Toledo


MK1 Skoda Octavia (1U)


02J Gearbox Codes

  • DEA, EBF, EGS - 30:39 = 0.769 as per T4b DCW
  • DQY, EBT, EGR - 34:45 = 0.756 as per T4b DCV, DJZ, DQJ, DQL, EVV, EVY
  • CZL - 33:46 = 0.717
  • EWX, EUH - 29:39 = 0.744 as per TDI DQH, DUH, EVW, EWA
02C (4wd) Gearbox Codes (as fitted to Skoda Octavia only)

  • EAG, EWK - 33:46 = 0.717
MK4 (9N) Polo


02R Gearbox Codes

  • EWT, GGU - 28:40 = 0.700 as per TDI
  • EWR, GGV, HET - 34:45 = 0.756 as per T4b DCV, DJZ, DQJ, DQL, EVV, EVY
T4/T5 Fifth Gear Sets

02B Gearbox Codes (T4a 1990 - 1995)

Caravelle

  • AYE, AYF, CCX, CCY, CHR, CHS, CRM, CRN - 34:45 = 0.756
  • CPV - 30:39 = 0.769
Transporter
  • AYD, AYG, CCW, CCZ, CHP, CHT, CRL, CRP - 36:43 = 0.837
  • CPW - 31:37 = 0.838
02B Gearbox Codes (T4b 1996 - 2004)


Caravelle

  • DCV, DJZ, DQJ, DQL, EVV, EVY - 34:45 = 0.756
  • DCW - 30:39 = 0.769
  • DUJ, EVU - 28:40 = 0.700 TDI Caravelle
Transporter
  • DCX, DKA, DQK, DQM, EVX, EVZ - 36:43 = 0.837
  • DCU, DQG, EVU - 31:37 = 0.838
  • DQH, DUH, EVW, EWA - 29:39 = 0.744 TDI Transporter
02D Syncro Gearbox Codes (T4a 1992 - 1995)


Cravelle

  • ARL, CRZ - 34:45 = 0.756
  • CRW, CLX - 30:39 = 0.769
Transporter
  • ARF, CLY - 36:43 = 0.837
  • CRV, CLW - 31:37 = 0.838
02D Syncro Gearbox Codes (T4b 1996 - 2004)



Caravelle
  • DCY - 30:39 = 0.769
  • DQP, EWD - 29:39 = 0.744
Transporter
  • DCZ, DQN, EWC - 31:37 = 0.838
Crawler / Mountain
  • DDA, DQQ - 32:47 = 0.681
02Z Gearbox Codes (T5 2003on) with part numbers


Caravelle

  • FJH, FJJ - 27:41 = 0.658
  • FJK, FJL - 23:37 = 0.622
Transporter
  • FJM, FJL - 31:37 = 0.838
Summary of "Overdrive" Ratios (with part numbers)


  • 30:39 = 0.769 (02A 311 361 N : 02A 311 158 L)
  • 34:45 = 0.756 (02A 311 361 Q : 02A 311 158 E)
  • 29:39 = 0.744 (02A 311 361 AD : 02A 311 158 AE) as per TDI
  • 33:46 = 0.717 (02A 311 361 M : 02A 311 158 R)
  • 28:40 = 0.700 (02A 311 361 AM : 02A 311 158 AF) as per TDI
  • 32:47 = 0.681 (02D 311 361 : 02D 311 158) as per T4 Syncro
  • 27:41 = 0.658 (02Z 311 361 A : 02Z 311 158 A) as per T5
  • 23:37 = 0.622 (02Z 311 361 : 02Z 311 158) as per T5
Gearbox end cover gasket - 02A 301 215 A
Gearbox end cover - 02A 301 211 A
Fifth gear syncro ring - 02A 311 295 C

But which is best?

Example

Let's start by comparing the range topping T4b (1996-2004) TDI with the basic T4a (1990-1995) 1.9 Diesel (normally aspirated - i.e. not the turbo charged model):

TDI - the 150bhp red "I"

  • peak engine torque = 295Nm developed between 1900rpm and 3000rpm
  • 5th gear ratio (02G) = 0.694:1
  • final drive ratio = 3.944:1
therefore
  • the overall top gear ratio = (0.694 x 3.944) 2.737:1
therefore
  • the overall applied torque at the wheels in top gear = (295 x 2.737) 807Nm tractive effort (or pulling power) between 1900 rpm and 3000rpm
  • top gear road speed at 2500rpm = 71mph
  • average fuel economy = 38.5mpg
Compared to


1.9D na with overdrive gearing

  • peak engine torque = 127Nm developed between 1700rpm and 2500rpm
  • 5th gear ratio (02B) = 0.756:1
  • final drive ratio = 4.941:1
therefore
  • the overall top gear ratio = (0.756 x 4.941) 3.735:1
therefore
  • the overall applied torque at the wheels in top gear = (127 x 3.735) 474Nm tractive effort (or pulling power) between 1700rpm and 2500rpm
  • top gear road speed at 2500rpm = 52mph
  • average fuel economy = 35.7mpg
F.A.Q's - those with Project Power vans based on the TDI - the 88bhp blue "I" should aim for the TDI gearing, whilst those with project power vans based on the 1.9TD should aim for the standard TDI gearing, bearing in mind that the standard final drive ratio remains as listed below
  • 4.235:1 as per TDI
  • 4.563:1 T4a/b 4-cyl 1.9TD, 5-cyl 2.4D na and 2.5 litre petrol models
  • 4.611:1 T4a/b 4-cyl 1.9TD, 5-cyl 2.4D na and 2.5 litre petrol models
  • 4.941:1 T4a/b 4-cyl 1.8 and 2.0 litre petrol and 1.9D na
  • 5.313:1 as per Syncro mountain gearbox (combined with the 0.681 fifth gear)
TDI based Project Power theorectical road speed at 2500rpm - 4.235 x
  • 0.744 = 62mph (standard Transporter). Tractive Effort (pulling power) 614Nm (std) / 929Nm (TDI)
  • 0.717 = 63mph. TE 592Nm / 896Nm (TDI)
  • 0.700 = 65mph (standard Caravelle). 578Nm / 874Nm (TDI)
  • 0.681 = 67mph. 562Nm / 851Nm (TDI)
  • 0.658 = 69mph. 543Nm / 822Nm (TDI)
  • 0.622 = 74mph. 514Nm / 777Nm (TDI)
1.9TD based project power theorectical road speed at 2500rpm (3000rpm) - 4.611 x
  • 0.837 = 50 (60) mph (standard Transporter). Tractive Effort (pulling power) = 540Nm (std) / 752Nm (TDI)
  • 0.769 = 54 (65) mph. TE = 496Nm / 691Nm (TDI)
  • 0.756 = 55 (66) mph (standard Caravelle). TE = 488Nm / 680Nm (TDI)
  • 0.744 = 57 (68) mph. TE = 480Nm (1.9D na = 474Nm) / 669Nm (TDI)
  • 0.717 = 58 (70) mph. TE = 463Nm / 645Nm (TDI)
  • 0.700 = 60 (72) mph. TE = 452Nm / 629Nm (TDI)
  • 0.681 = 62 (74) mph. TE = 440Nm / 612Nm (TDI)
  • 0.658 = 64 (76) mph. TE = 425Nm / 592Nm (TDI)
  • 0.622 = 68 (81) mph. TE = 402Nm / 559Nm (TDI)
Gearbox Codes: CCY, CHS, CRN, AYD, CCW, CHP, CRL, DJZ, DQL, EVY, DKA, DQM, EVZ




the alternative 1.9TD set of figures - 4.563 x
  • 0.838 = 50 (61) mph (standard Transporter). TE = 535Nm
  • 0.769 = 55 (66) mph (standard Caravelle). TE = 491Nm
  • 0.756 = 56 (67) mph. TE = 483Nm
  • 0.744 = 57 (69) mph (standard Caravelle). TE = 475Nm (1.9D na = 474Nm)
  • 0.717 = 59 (71) mph. TE = 458Nm
  • 0.700 = 61 (73) mph. TE = 447Nm
  • 0.681 = 62 (75) mph. TE = 435Nm
  • 0.658 = 64 (77) mph. TE = 420Nm
  • 0.622 = 68 (82) mph. TE = 397Nm
Gearbox Codes: CPV, CPW, DCW, DQH, EVW, DCU, DQG, EVU

These road speed figures also relate to the 2.4D na and 2.5 litre petrol models - what differs is how quickly the vehicles arrives at those speeds. For the clculation I have used an overall wheel rolling diameter of 26" (661mm) - the acceptable range (without affecting speedometer accuracy to any significant degree) is from 25.5" to 27".

It is worth noting that fitting tyres of a larger diameter will have similar incremental gains in road speed through all the gears, not just fifth gear.

The standard 1.9TD produces 140Nm of torque between 2000rpm and 3000rpm. Each project power van will undoubtedly produce more power but each power band and output will be different. As we are aiming to equal or better TDI figures, I have included them for comparison purposes only, as I have with the TDI to TDI figures (these speed figures do not apply to TDI Project Power which have the 02G gearbox).

And not forgetting the 2.0 litre petrol models...




Theoretical road speed at 2500 rpm - 4.941 x
  • 0.837 = 47mph (standard Transporter). TE = 658Nm
  • 0.769 = 51mph. TE = 604Nm
  • 0.756 = 52mph (standard Caravelle). TE = 594Nm
  • 0.744 = 53mph. TE = 584Nm
  • 0.717 = 54mph. TE = 563Nm
  • 0.700 = 56mph. TE = 550Nm
  • 0.681 = 58mph. TE = 535Nm
  • 0.658 = 59mph. TE = 517Nm
  • 0.622 = 63mph. TE = 489Nm (1.9D na = 474Nm)
Gearbox codes: AYF, CCX, AYE, CHR, CRM, AYG, CCZ, CHT, CRP
 
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