Insert your tranny experience here

[cantrun10s]

Hi guys, new to the forum, blah blah blah.

Question - Got a 94 PSD with a ZF 5 speed that I'm going to rebuild, or replace. Trans isn't flat out broke, just needs synchros. I was thinking of just picking up a 6 speed, as I do tow alot, and the closer ratios look kinda nice to me.

Any of you running this trans in an older truck with some insights?
What to expect during the install? Any input would be appreciated. I haven't really come to a final decision yet, and I'm still trying to figure out where to get the bell I'd need to do it. Like I said, any opinions are welcome. Thanks guys.

[TxPSD9673]

well im not sure but i sure would like a zf6 in mine! cus i sure hate doin 2600rpm at 80 lol but heres a bump for ya

[Dallas4x4]

Mine doesnt like to be shifted into 3rd fast or go into reverse.
and im intrested in the zf6 swap too. Because mine is gona blow one day and hate going slow at high rpm.

Im pritty sure it would bolt upto the engine but not to sure about the bolting upto the t-case.

You should of put "ZF5 to Zf6 Swap?" as a title. Probaly would get more help full responces.

[nick_ava_06]

i am looking at the same swap. i got a 97 5sd duallie. so far i have not found a problems intherory it should bolt right in but..... and well if there is a problem get a bigger hammer or a fresh saw blade

[nsrchofpwr]

subscribed. it is always nice to know what works and what doesn't.

[BudDog]

Yeah I like the idea of having a 6 speed. But I have driven a few ZF6's and I dont like to have to find 1st gear. In mine its all the way to the left and down
. On a 6 thats reverse. Low gear in behind it then you have to find 1st instead of 3rd. I still like the idea of having a 6 speed and I might buy one but Im looking for an automatic right now.

[cantrun10s]

Made up my mind... or rather the 5 speed made it up for me.
I'm gonna do it. I wont be able to help you guys with transfer case info, as this truck is a 2 wheeler. I'll post pics and info as I go, but dont expect super-speedy results. The demolition is scheduled to begin next Monday. Need to put one last run on the five speed, without second gear, 12k# load. This should be fun.

[Big K]

I believe a few have done this conversion, but it isn't just BOLT ON application....

As I understand it, the bell housing will bolt directly to the block. Fabrication is needed for the cross member as the ZF6 is longer/larger. You cannot use the same clutch from a ZF5. It will require some modification. Also, due to the ZF6 being longer, the rear driveshaft has to be shorter.

Not to mention, if yours is 4WD, you will have to modify the TC also....

[Rantheman]

I believe your transmission is a ZFS5-42 which mine is a ZFS5-47 but really the only benifiet of the ZF6 is the Higher Tourque Rating of 520 Ft-lbs but here is some specs for you to look over.

ZF S5-42 – 5 speed manual transmission has an aluminum alloy main gear case and tail housing with the bell housing integral to the case.

The ZF S5-42 is built in both a 2 wheel drive and 4 wheel drive version with gas and diesel designs

ZF first introduced the S5-42 in 1987 and was used in the Ford F250, F350, F450 and Super Duty trucks until 1994.

All gears on the S5-42 are fully synchronized with an input torque rating of 420 ft-lb

Standard gear ratios on the ZF S5-42:

Close Ratio
1st Gear: 4.14
2nd Gear: 2.37
3rd Gear: 1.42
4th Gear: 1.00
5th Gear: 0.77
Rev Gear: 3.79
Wide Ratio
1st Gear: 5.72
2nd Gear: 2.94
3rd Gear: 1.61
4th Gear: 1.00
5th Gear: 0.76
Rev Gear: 5.24

The ZF S5-42 main case cast number is “1307”

ZF S5-47 – 5 speed manual transmission has an aluminum alloy main gear case and tail housing with the bell housing integral to the case.

The ZF S5-47 is built in both a 2 wheel drive and 4 wheel drive version with gas and diesel designs

ZF introduced the S5-47 in 1995 and was used in the Ford F250, F350, F450 and Super Duty trucks.

All gears on the S5-47 are fully synchronized with an input torque rating of 470 ft-lb

Standard gear ratios on the ZF S5-47:

Close Ratio - 7.3L Diesel
1st Gear: 5.08
2nd Gear: 2.60
3rd Gear: 1.53
4th Gear: 1.00
5th Gear: 0.77
Rev Gear: 4.66
Wide Ratio
1st Gear: 5.72
2nd Gear: 2.94
3rd Gear: 1.61
4th Gear: 1.00
5th Gear: 0.76
Rev Gear: 5.24

The ZF S5-47 main case cast number is “1317”

ZF S6-650 – Heavy Duty 6 speed manual transmission has an aluminum alloy main gear case and tail housing with the bell housing integral to the case.

The ZF S6-650 is built in both a 2 wheel drive and 4 wheel drive versions with a diesel design only.

ZF first introduced the S6-650 in 1998 on the Ford Super Duty and compatible stripped chassis’s.

The S6-650 has a an internal oil pump to circulate and cool the lubricant which is unique to a manual transmission.

All gears on the S6-650 are synchronized with a dual cone synchronizer in 2nd and 3rd gears with an input torque rating of 520 ft-lb.

GM started using the ZF S6-650 in 2001 with some improvements making this 6 speed transmission different from the Ford version.

Standard gear ratio on the ZF S6-650:

1st Gear: 5.79
2nd Gear: 3.31
3rd Gear: 2.10
4th Gear: 1.31
5th Gear: 1.00
6th Gear: 0.72
Rev Gear: 5.23

The ZF S6-650 main case cast number is “1319”

[metallitera]

6th gear and 5th of the 5spd are not that different, ive been wanting to do the same, but am also thinking of any manual that international used in their trucks. maybe an 8 or 9 speed would have higher top gears, and the bell housing should bolt right up, just a clutch and flywheel issue now.

i just dont know where to start looking for medium duty truck trannys that would work.

or would there be anyway to rebuild the 5spd or 6spd with like a 0.50 or 0.40 top gear?
maybe gear the 6spd like the 5spd and add that TALL gear as 6th?