Hello, all. I have a 1980 F100 with a 2.75:1 rear. The trans is a 3spd column shift. 1st gear synchro is worn from previous owners' maladjusted manual clutch pedal. (When I bought the truck, you could feel the synchro being trashed as you engage 1st ... bummer.) Clutch is adjusted now but the damage is done. 1st gear pops out on deceleration and occasionally grinds due to not being engaged fully from the worn out column linkage. There's no adjusting it, either. If the shifter rod is adjusted to engage 1st more firmly, then sometimes the column shift mechanism jams between gears and can only be fixed by moving the shifter rods manually. Getting out of your truck to shift is not an option ...

With this 2.75:1 rear, this trans' 1st gear is pretty steep. Clutch chatter is basically unavoidable with any weight in the bed or being towed. The idea occurred to me to put a T18 or T19 trans in the truck. There are various ratios available on the T18 and T19s. I did some calculations to see how engine speed would be at 10 mph w/ my 29" tires (235/75/15) in the creeper gear.

T-18 w/ 6.32:1 1st @ 10mph = 2014 rpm.
T-19 w/ 4.02:1 1st @ 10mph = 1281 rpm.
T-19 w/ 5.10:1 1st @ 10mph = 1625 rpm.
T-19 w/ 6.32:1 1st @ 10mph = 2014 rpm.
NP435 w/ 4.78:1 1st @ 10mph = 1523 rpm.
NP435 w/ 6.69:1 1st @ 10mph = 2132 rpm.

For comparison, my 4spd overdrive '86 F150 in 1st with 3.55:1 rear & 27.7" tires @ 10 mph is around 1500 rpm (must be about 3.5:1 1st gear). This rpm and wheel speed is good for moving weight.

So, for the swap, I think the 4.02:1 T-19 sounds best. That has a smooth spread across the higher gears, also. A guy near me has 2 parts trucks, an 86 F350 and an 80 F250 with 4spds. I'll need a trans and driveshaft for this swap, and I'll need the driveshaft shortened (7' bed on the F100). I have to go look at his trucks to identify the transmissions. NP435 has a flat bottom, T-18 & T-19s have a tapered bottom on the tailshaft side. T-18s have 1 PTO cover, T-19s have 2.

Will the manual clutch linkage work from the 3spd to the T18 / T19? Is there any way to identify transmission ratios other than counting the turns of the input & output shafts? Will speedometer cables interchange? Does anyone know my current trans model & ratios? Also, feel free to share your input on the swap idea.

Thanks, all.

 

What motor does the truck have I am think the 300 six with the rear gear.
For the trany in the truck I take it it is factory and if so what does the cert sticker inside the left door have for a trany code?

I also don't like picking a speed like you did for gear but I guess it could work.
I like to take all the ratios for each trany and see what the final is with the rear gear you have.
I find this helps when knowing what you have now and how it drives and then looking over the other tranys ratios and compare them.

First information I have on the T18/T19

T18A = 6.32, 3.09, 1.69, 1.00, rev- 7.44.

T18B = 4.32, 2.26, 1.51, 1.00, rev- ?

T18 & T19 = 4.02, 2.41, 1.41, 1.00,rev- 4.73. (Close Ratio)

T19 = 5.11, 3.03, 1.79, 1.00, rev- ? T19 has synchro 1st gear

Here is what I figured for my T18B with a gear vender OD unit

T18B = 4.32, 2.26, 1.51, 1.00 & GearVender Over Drive Unit = 0.78

4.32 x 2.75 = 11.88

4.32 x 2.75 x .78 = 9.27

2.26 x 2.75 = 6.22

2.26 x 2.75 x .78 = 4.85

1.51 x 2.75 = 4.15

1.51 x 2.75 x .78 = 3.24

1.00 x 2.75 = 2.75

1.00 x 2.75 x .78 = 2.15

Dave ----

 

Hey thanks for the reply. Yes it is a 300. Trans code C, Ford 3.03 3 speed. Good thinking, the door jam sticker.

Vehicle speed & engine rpm calculation accounts for tire size, rear ratio, trans ratio all in one.

Is there a way to tell a T-18A from a T-18B? Do they have different internal gear ratios? Any idea on what ratios the 3.03 had in a 1980 F100?

 

I want to say there were casting number/letter on mine, don't remember where on it, that I found when de-greasing it before painting and putting it back in my truck.


Check on the side for the number/letter.


Transmission Codes - ???Gary's Garagemahal
It is a Ford 3sp trany but no ratios on his site.


Closest I could come on ratios thru Google
https://www.ford-trucks.com/forums/4...ear-ratio.html
Ford transmission normally used behind the 300-6 and 302 in 1978

Normal ratio: 2.99 1.75 1.00 R3.17
Wide ratio option: 3.26 1.91 1.00 R3.46
Don't know how right that is?
Dave ----

 

Thanks for the 3.03 trans info. Yeah, it is hard to find a lot out about these! Bummer the column mechanism wears so badly ... This 4spd idea has me excited to have a lower 1st and reverse for towing, also.

 

I wish I could say what mine is like (with out the gear vender OD) but other than a short test drive and on/off trailer I have not driven mine.


Mine will be used as a back up to me DD and to pull my car trailer when needed.
The granny low should be good when pulling/towing a heavy load. Other wise you start off in 2nd gear normally and drive it like a 3sp.
Dave ----

 

Subscribed. Curious what you end up doing.

I have an '82 F100 - 300 - 3.03 RAT 3-speed. I've got a good (looked-over by a local trans shop) T-18 that I haven't installed yet because I don't have a driveshaft solution to get from the fixed-yoke T-18 to the fixed-yoke 9" (2.48 rear gear!!!).

It IS confusing, with all the wheelbase/powertrain/drivetrain combos for these early-80s trucks!

 

Hey thanks, I'll update this thread as progress progresses. Just sourced what I think are all the parts I need - T18, bellhousing, dust cover, and the floor cover panel w/ shift boot.

A local shop I'm friendly with and work part time at recommended having a custom driveshaft made, because of the dual fixed-yoke setup. Driveshafts can be made one-piece with a slip joint in the middle. The driveshaft from the donor truck was a two-piece, whereas my truck has a one-piece.

And yes, there were a ton of options on these old trucks. Super cool finding used ones for sale because of all the things that can differ among them.

 

Getting closer to starting this project. We took our 1984 E350 Holiday Rambler to FL and avoided a series of harsh nor'easters. We'll be back in a couple weeks.

What clutch can I get for this project? LUK and Sachs make a few models. I don't know if the input splines are the same between the old and new trans.

 

If it's a Ford T18, it should have the same/right spline count, as long as you buy the same clutch for your original application, everything should work. If possible, you should use your original 3.03 bell housing on the T18 to make sure it goes together right

 

I don't know who made my clutch kit but I got it thru Car Quest Auto Parts.
I may still have the box with the old parts in it and will check next time out in the garage.
I want to say it was a 10" disc and had 10 count splines but the spline count could be wrong.

What I do if I want to know if parts will work from other models or years is look the parts up on line and see if the part numbers are the same.
Look up the clutch kit for your year truck & trany then look it up for the year truck the new trany (T18?) came out of.
If you don't know the year use mine, 81 F100 with a 300 six & T18. If you need more information let me know

Now it has been posts that the flywheels "may" be drilled / tapped for 11" disc. If so that would be an option when doing a clutch.
I cant remember if mine was drilled or not for the 11" disc and the kit had a 10" so that is what went with.
Hope that helps some.
Dave ----

 

Thanks for the replies, guys. Sounds like the input shaft spline counts should be the same. I'll certainly know once I start pulling it all apart! Maybe I can peak in through the dust cover first, too.

Looking forward to giving this truck a new set of gears. I think it'll feel so much better. Moving weight around in a trailer is torture on this clutch.

 

The T18 swap begins. The trans I have looks good internally. The shifter "pin" on mine appears to have been a 1/4 - 20 bolt at one point in its life I plan on welding the worn shifter ball slot and grinding it to fit the new shifter pin, saving $75 vs. replacing the whole lever. The T18 will be filled with 50w oil. The crossmember looks to be in the correct location and even drilled for the shorter T18 to mount in.

Next came speedometer calibration ... new tires are in order this year. Stock this truck takes 195 75 15. It currently has 235 75 15 tires. After playing around with tire size dimensions and the 2.75:1 rear, I calculated what speedometer drive and driven gears are needed. 215 75 15 tires require a 7 tooth drive gear & a 14 tooth driven gear, but a 14 tooth isn't available. The drive gear will have to be changed to an 8 tooth, and the driven gear to a 16 tooth. This will be accurate (according to calculations).



An unforseen hurdle appears to be the speedometer cable. The boss entering the 3 spd manual is very large, whereas the T18 speedometer cable is a lot smaller ... anyone know more about this? The listings for manual or automatic 1980 F100s all picture a smaller boss speedometer cable so maybe mine is not an original trans, don't know. I suppose I'm ordering a new speedometer cable as well!

After swapping speedometer gears, repairing the shifter, cutting a hole in the floor, swapping the new flywheel, clutch, trans, and having a driveshaft made, and this project should be done. Unfortunately it's being juggled with my self-employment (spring lawn equipment repairs) so I will report back when there's more to report.

Side note - the 1984 E350 motorhome took us over 4000 miles this winter from PA to St. Charles, Louisiana, Tampa, Florida, and back. 7.6 mpg avg towing a Ford Focus on a 500 lb tow dolly. Wonderful machine and wonderful trip.

 

Interesting. I thought the speedometer cable connections at the transmissions were all the same. I swapped a 3spd manual column shift to a 5spd, and the existing speedo cable worked just fine. Plugged it into the 5spd and everything worked as normal.

 

It sounds like you have a good game plan on the swap.
You may want to rethink the W50 oil as I am sure the T18 took W90 oil.

Any way to get the speedo cable from the truck the T18 came from?
I would think the cluster end would be the same on all 80 - 86 trucks.
Mine is still not on the road so cant tell you how it is with the T18 or speedo being right or not.
Dave ----