changing fifth gear to a taller ratio

Tony,

Best place to start:

http://www.rbttrans.com/index.html

Larry

Tony,

I installed the tallest 5th gear Lloyd Butfoy makes. It's a .620, this knocks 500RPM off the engine and achieves a satnav indicated 100MPH at 4000RPM with a 4.22 ring and pinion.
It's the best single improvement I have made to the car. I did not want a 3.77 as I have 335/17 rear tyres.

It makes high speed cruising much more enjoyable and quieter!

I also have a 1984 Porsche 911 3.2, this pulls a satnav indicated 100MPH at 4000RPM as standard so I think the Pantera is a bit low geared anyway.

I dont know about pricing you need to talk to Lloyd.

Johnny

There are a variety of ratios available both for a change of ring & pinion and for changing only 5th gear. The stock ring/pinion was 4.22:1 and many if not all post-80s Panteras had a 3.77:1 ratio. A slightly modified Pantera engine can pull this taller gear with ease, and it gives better mileage and a more relaxed high speed cruise. Changing only 5th gear gives you the same cruise rpms but the stock lower R & P ratio still allows stock acceleration. Both methods are equally expensive and both require the entire transaxle to be disassembled, so now is the time to decide, since its presumably apart already.
FWIW, RBT Transmissions in the U.S long ago bought the world-wide rights to that model of ZF transaxle so all official parts- from gaskets to gears- will come from them. Others that sell such things are usually cannibalizing useable bits from broken ZFs, or they are not true factory parts. Caveat Emptor!

thanks for the advice guys i will contact Lloyd and get some prices as my zf is being rebuilt it would be maddness not to do this mod now ,my zf has a 4.22 diff in it , i am putting a tuned engine and am expecting around 450 bhp cheers tony

I really like the existing ZF gearing and especially how the ratios get progressively closer at higher speed. It seems like a 6th gear is the best of all solutions.

Mike

The 215/70VR15 tires that were oem on Panteras were 26.8" diameter. The H60 tires on the Ford spec Pantera L were 27" diameter. The 285/50VR15 Pirelli P7s on the Euro GTS Panteras were 26.2" diameter. All these Panteras had the 4.22:1 gearing as standard equipment.

The GT4, GT5 and GT5-S Panteras had 345/35VR15 Pirelli P7s which were only 24.5" diameter, that is why those cars were equipped with taller gears, most often 3.77:1 or 4.00:1.

Installing a ring and pinion with a higher gear ratio (smaller numerically) has the effect of giving the car a wider ratio gear box, you may like that, you may not. It would depend upon how you drive your car. The standard 5th gear in most Panteras is 0.846:1. Here's the overall 5th gear ratio for the 4.22:1 ring and pinion, and the available higher ratio ring and pinions:

4.22 x 0.846 = 3.57:1 (standard)
4.11 x 0.846 = 3.47:1
4.00 x 0.846 = 3.38:1
3.77 x 0.846 = 3.18:1
3.56 x 0.846 = 3.01:1
3.44 x 0.846 = 2.91:1
3.20 x 0.846 = 2.70:1

An over drive 5th gear is much less expensive than a new ring and pinion however, it allows the gear spacing to remain the same while providing a more relaxed crusing gear, and a higher attainable top speed. Here's how the available higher 5th gear ratios affect the overall 5th gear ratio with the standard ring and pinion:

4.22 x 0.846 = 3.57:1 (standard)
4.22 x 0.740 = 3.12:1 (about the same as using a 3.77 ring and pinion)
4.22 x 0.704 = 2.97:1
4.22 x 0.655 = 2.76:1
4.22 x 0.642 = 2.70:1 (same as using the highest ratio ring and pinion available)
4.22 x 0.620 = 2.61:1

Changing the 5th gear is the economical way to achieve a more relaxed cruise rpm. I've never known anybody to regret installing the overdrive 5th.

-G

thanks for the great advice guys do you guys have a idea of what price you would pay for a .642 or .620 fifth gear ,as i like the idea of standard ratios thru the box and a taller fifth as a overdrive gear cheers tony

from the link above....

1887, be aware that the 6-speed ZF, developed for Ford's GT but then not chosen, is indeed available from RBT Transmissions- at least two are in U.S Panteras. The cost is less than the gigantic Ricardo trans that was chosen for the Ford GT, and uses the same cases as original with a 4" extension to house the new 6th gear. The shifter works unaltered, the bell housing and trans mounts fit as-stock and the only known mod is a small notch needs to be cut or bent up on the A/C shroud bottom (if its still in back on your car; many have been moved to a more efficient front mount) to clear the slightly longer cases. Lloyd at RBT could tell you if the 6th gear could be installed in your ZF, or what if any "trade-in" value your ZF has with him on the upgrade. FAX is the best way of contacting him.

quote:

Originally posted by Cowboy from Hell:

The standard 5th gear in most Panteras is 0.846:1.

-G

George, The RBT Configurator defaults to a .704 5th gear for the Pantera. Please explain. Thanks.

Ron

My -2 that is in my 71 has a .705 5th There is a gear, tire and RPM calculator on this page that might be helpful http://www.panteraplace.com/page32.htm

Mike

quote:

Originally posted by rlee63a4:
The RBT Configurator defaults to a .704 5th gear for the Pantera.

Explain? Memory lapse (old age, alcohol) ... the earliest cars had an 0.846:1 ratio fifth gear, but sometime in 1971 (June?) the gearbox ratios were changed. Most Panteras have the 0.705:1 fifth gear, and fourth is actually 0.846:1. I plain forgot about that.

I apologize if I mislead anyone, thanks for keeping me honest Ron.

-G

I had installed the overdrive fifth gear in my ZF and loved the results. I paid approx $1500 for the gear by itself and had Les Gray install it. I had spoken with Lloyd one day when he was at PI Motorsports and he happened to be driving his test car that had the 6 speed installed in it. He personally recommended the overdrive fifth gear, over the 6 speed ZF.

I also had the 0.642 5th installed and it cost $1500 extra while the box was apart for a rebuild. Without a doubt one of the best mods I have done. There is a guy in the UK that has a good reputation with ZF's, although his name slips my mind (Phil?). Johnny Woods would probably know.

A bit of thread drift but I would refute Jack's (Bosswrench) statement that a 6 speed ZF is cheaper than a Ricardo, as reconditioned Ricardo's sell for $6500 and a ZF 6 speed is somewhere around $16K now. However the Pantera chassis requires heavy modification to fit the much larger Ricardo.

Another alternative is the ZFQ made by Quaife for the GT40 guys, it is dimensionally the same as the ZF -2, has CV outputs and a 3.75 diff as std. and cost was GBP6500.

Julian

Does anyone have a ZFQ in their Pantera?
Chris Melia at Gttransmissions in UK say that Quaife never made the crown wheel and pinion for the inverted mount.
He claims that the Quaife website is wrong on that matter.

quote:

Originally posted by Tunnelport492:
Does anyone have a ZFQ in their Pantera?
Chris Melia at Gttransmissions in UK say that Quaife never made the crown wheel and pinion for the inverted mount.
He claims that the Quaife website is wrong on that matter.

I have had several friends tell me they inquired and were also told that ZFQ is not available in Pantera configuration though I thought the reasons were that the work was never done to insure proper lubrication during inverted operation as opposed to the inability to flip the orientaion of the ring and pinion.

Best,
K