Part l:

From the start one thing was certain, I didn’t want a show car, but a GT to drive on a daily basis. Even if you had to do some modification more reliable and trouble-free technology should be integrated. 

The 2-liter Injection engine was already a successful step in this direction. In addition to the increase in efficiency, modern electronics will be noticed in each situation. Absolutely trouble-free cold start, chop-free, best acceleration, quiet, and better fuel economy, approximately 10.5 liters/100 km or 22.4 mpg fully loaded.   Weak-points emerged; however, in the combination with the original GT - 4-speed-transmission: frequent shifting in the city, too short 1st gear and wheel spin. 

The 2 liter FI engines rev up quickly on the highway in the GT. With the one look at the tachometer I was frightened to see the effects of 6200 revs/minute on the effort and the expenses of an engine change.  These sound effects with can be endured only with a grim expression over a long period of time. For sure the engine could have been revved even higher.  I also would like to drive faster, but anyone hearing the tack-tack-tack announcing a failure of the rod bearings, can live without it for the next 2 or 3 years.      

Speeds beyond 180 km/hs (110 mph) are a bit nerve-racking and should only be endured for a short time. But you can live with a reasonable noise level and engine rpm’s at 160 to 170kph (100-105mph.   Finally, to the subject of this document: The 5-speed transmission with final overdrive gear appears to be the optimal solution.  The rear axle ratio remains as is and acceleration will remains as is. You can shift into an additional gear and glide quietly and virtually without noise. Those were my thoughts, theoretically.  

Practically it looked different. I ignored the original optional Opel/ZF-transmission because of its high noise level. I concentrated my search on one, the Getrag 240, with the fifth gear .803 final drive ratio. Like many of you know, it’s not easy to find this type.

After some searching, I was lucky to buy a Getrag 240 from a Record E with 47,000 km (29,000 miles) for 700, - DM.($325 USD). The tranny looked rather huge, like it wouldn’t fit in the GT transmission tunnel.

I did some research and concluded that, without question, the gearshift extension would have to be shortened. Additionally, I would have to bend the gearshift to fit exactly. I built a mock-up of the original to test fit. See Fig. 1

I built a wooden plate and inserted 4 dowels to mate to the bellhousing. The pivot point of the shifter plate is also simulated with plywood and dowels.  Abb.2.   A piece of cardboard is also used to estimate the location of the shifter while in the neutral position of the shift pattern. (fig.) 3). In addition, it establishes the length of the travel for the 5-speed mechanism.  The Getrag mechanism 5-speed mechanism is different from the original 4-speed shifter principle. It only has one cross-connecting link, that leads from the front to the back of the body of the mechanism. The gearshift lever is attached to the shift plate with a ball-joint and connected with the shift linkage. This construction already leaves the possibility of a precise shift pattern suspect.

The rebuilt mechanism is in Figure 1.

Step 1   Cut out rear tab piece and reattach to reinforce the front of the shifter attachment bracket.  

Step 2   Cut shifter mechanism from rear of bracket along line illustrated in drawing.  Trim the side pieces from the shifter mechanism and leave a rectangle approximately the size of the center section of the shifter mounting plate, see illustration.  

Step 3   Cut center section from forward portion of shifter mounting plate as illustrated in the drawing.  

Step 4   Weld in shifter mechanism as illustrated.

Step 5   From the separated piece cut out the baseplate with the nylon bushing and shifter assembly. Do not drill the spot welded points.   Cut out an opening to fit in the baseplate. Do not weld yet.   Baseplate “A”, u-joint and bolt already installed Cut the pull-rod and drill a hole in the base of the u-joint to have the parts welded easily.   The pivot-head for the shift linkage fits in the socket.    

Step 6   The socket has to be rotates approximately 10 - 15° counter-clockwise on the axis of the transmission at the linkage weld point. This places the shifter in line with the GT engine tilt.  

Step 7   Cut out the bend in the gearshift lever (approximately 2 cm) and weld the lever together again by placing it 6 mm in driving direction.   Important: when welding several times in the same place, water quench the part to prevent the lose of tensile strength at the welded joint.      

Step 8   Mounting brackets " B " with ball-joint - Hold-plate welds Mechanisms into the idle switch. All Parts together-are as well as schrauben. In the teaching checks, whether that cross-connecting - stick in the right angle stands. The shift plate is temporarily assembled to test the operation of all parts. If necessary, you can correct the angle of the linkage. The final position of the linkage is based on this observation. Check all the shifter parts for function and clearance. If everything is properly positioned at the right position and the mechanism shifts without problems everything can be welded solidly. The linkage rebuild is complete. It is somewhat more simple to understand everything, if you have the transmission in front of you at the time.   In the next issue: Installing the Five-speed gearbox in the GT.    

Part II: Installation of the Transmission     In the last issue, I described the rebuilding of the shift linkage on GT-dimensions, or at least how I rebuilt it. It probably works for other applications. At first I thought about just moving the opening for the shifter, but that’s not likely to be the most surgically correct method and doesn’t help to keep the value of the car.  It is not necessary, if you, as described in Part I, rebuild the shift linkage. It fits! That was my goal.    

Installing the gearbox   Thequestion was: Will the 5-speed bell-housing and transmission-unit, mate to the engine? In a section of the workshop literature it is represented that the GT engine and transmission must be removed as a unit. “Do you have to remove the engine to get the transmission installed?”.  Maybe? I couldn’t figure it out, so I asked around.   That now comes also into brooding,:   Z. B. Starters, mechanisms etc Five-speed gearbox in the GT    

Now with a bit of serious thought:   IT IS POSSIBEL! I haven’t had any problems removing the original 4-speed and replacing it with the 5-speed.   First I had to remove the radiator. Then raise the GT off the ground approximately 60 cm (2 ft.) in the front and rear at the jack points. Not who over the suitable Decreed aids, should itself to this stable, high bucks and a hydraulic car - lifters lend.   Drive shaft and gearshift levers develop, Speedometer-wave and reverse light-counters clamps. If the rear transmission cross-member is unbolted the transmission comes down in one piece. The problem is un-bolting the bell-housing. I used a super long extension with a universal joint for badly accessible bolted connections, starter mechanisms, etc    

Instead of the big extension you can also use three short extensions together. Loosening of the bolts on the bottom is easy. After the transmission is bolted on, the motor is easily lifted in front using a jack with wood inserted to prevent damage to the oil pump cover.  The pump is exposed and can easily be damaged. At this point the engine is at a steep angle, and care should be taken not to strike other parts of the engine compartment.     

With injection engines the cold start-valve at the suction tube area is a tight fit. Therefore, a helper must watch that the cold - start-valve doesn’t hit the windshield wiper posts. With a carburated motor the throttle linkage should be protected so that it is not bent. The exhaust moves some with the movement of the engine and should be disconnected at two mounting points. You should take this opportunity to inspect the condition of the clutch, if necessary replace the clutch, pressure plate and throw-out bearing.   It’s also necessary to check the oil level in the 5-speed transmission before installation. The inspection plug is a 17 mm Hex head socket screw. The Getrag 240 holds 1.5 liters (apprx. 3 pints) of gear oil. My transmission was a missing about 1 liter (2 pints). That would be embarrassing when trying to test drive.    

Before bolting the Getrag in place, you must install the original 4-speed clutch release arm. The lever is identical, except in the mounting of the clutch cable, the GT has a ball-piece, the Getrag, a threaded screw and ball. An alternative is to swap the clutch cable. Then, the comfortable adjusts slips however - possibility the clutch above in the motor - area.    

Now you can start to fit in the Getrag. With some feeling and something That works out jerk-in straight away. The completed gearshift-assembly (hold-angles " B ") see part l, remains dismantled during installation. After the installation of the transmission complete the installation of the shift linkage.  Now, check the position of the shift pattern in the vehicle.  If it is incorrect it can be repositioned and corrected, see Part l.    

The wires for the reverse light switch must be extended, since switch on the other side of the transmission. Also the transmission cross-member on the Getrag 240 sits 9 cm further to the rear than the original cross-member. The rear transmission mount must be used from the Getrag,   Opel Part- No. Q6Q 2515, price 41,36 DM + VAT ($20 USD + Tax).  I didn’t want to cut the original GT transmission rear cross-member. I have duplicated the corresponding tilted profile out of zinc-coated sheet metal, see sketch.      

This sheet metal strip was installed after being cut, bent in to a vee-eight re-welded. When this cross-member was ready, it still appeared the mechanism sat too low. Therefore, I put another 8 mm thick aluminum-block between the cross-member and rubber. If not done, the drive shaft would bend at too severe an angle. You can control the height of the transmission based on a comparison measurement from the stock-GT.    

Remove material from the sheet metal edge of the gearshift hole  Remove material until on the driving shaft with the Original-GT approximately 120 mm, beim Five-speed approximately 117 mm, tail-piece on the drive shaft has a larger diameter. The bolt-up of the Getrag connection of the transmission cross-member takes place in the holes for the for the automatic transmissions. Fig.,   Drive shaft    

The tail-shaft of the 5-speed transmission is larger at the rear than the original manual transmission. It closely matches the Opel automatic transmission tail-shaft. Unfortunately, the GT’s available automatic transmission drive shaft doesn’t fit either.  It’s to short for the Getrag. Therefore, the Automatic drive shaft must be lengthen and the flange mated for a U-joint. At a salvage yard a drive shaft from an Ascona (1900) cost 30-40 DM ($12-15 USD).  

This drive shaft must be properly shortened to the correct length and re-welded. Here, do-it-yourself is absolutely prohibited. You can improperly weld the seam and structurally alter the material that may ultimately lead to failure of the drive shaft. For safety reasons, the re-welds must be thoroughly inspected for hairline cracks.  Also the balancing can only be done on specialized equipment. Balancing is no problem, if he has a fitting for an Opel drive shaft.    

If this service is not available, you could go to one of the GT mail order suppliers. There you get a drive shaft that has already been shortened and re-balanced. Prices range from 200-300,-DM ($90-140 USD), time of delivery approximately 2-3 weeks, they also do also do custom orders.  The use of the automatic transmission drive shaft is somewhat less expensive.   However; it is more important in my opinion to have the guarantee that the drive shaft is expertly welded and balanced. Improperly constructed and unbalanced drive shafts could break a nice hole in the floor board or other consequences that you can imagine. Additionally, an unbalanced drive shaft considerably reduces the joy of driving. Ask specifically, before you buy it.  

Speedometer-adjustment  

The connection of the speedometer cable to the 5-speed transmission is no problem, only the speedometer will register 40 km/h (25 mph) too slow. This can be remedied by calling the VDO Factory. The branch office in Hanover has been very cooperative and friendly in the past.    

Since one something similar, particularly as GT-drivers, not at all more know, I like to mention it. A test of relationship between the numbers of rotation and the distance the whells rollof thethe rolling lenght brollversuch first became through - led, i.e., a marked route became departed and with help an on them/her/it Speedometer-wave of pretentious gauge the register was determined. The register indicates the number of turns the speedometer gear must make to register one kilometer. With my car with 205/60 tires, original 3.44 rear axle and the 5-speed with a blue pinion in the speedometer.  The register was W = 685. VDO can re-calibrate a speedometer, in principle however, not this speedometer. That leaves for this reason Legislators only one deviation of 4%    

Speedometers -   from the real value to, since otherwise that Meter a later buyer of the drives - stuff's a too low mileage vorlügen would become. The GT had two different speedometers installed. The older models with W = 557, the newer with W = 660. The difference can be compensated for in the W 685 and W 660 at the speedometer. My speedometer; however, is a W = 557. For this VDO has a new speedometer replacement mechanism. The new mechanism is the size of a matchbox, sees fig.  Speed and distance are exactly indicated. Incidentally, variances in the speedometer, faster or slower, can be adjusted. The cost for this without VAT (Tax) and with the use of your original speedometer mechanism is:   Labor, 18-DM ($7.00 USD) Differentials, 46-DM ($21.00 USD) 2-speedometer gears, 50-DM ($22.75 USD)  

The speedometer mechanism should not be lubricated by any means.  It is already permanently lubricated, despite the fact that it has a provision for lubrication. An excessive amount of lubricant on the mechanism will completely ruin it.