300 inline 6/ 3spd - 5spd conversion

[biggj]

Alright here goes, I have a 68' with the 300 inline 6 and a 3 spd. everything works pretty good on it, but I want more overdrive, it has a factory 3.70 geared 9in. rearend. I bought a t-5 transmission that was supposed to have come out of a early 80's mustang gt. I was wondering if anybody could point me in the right direction toward swapping this one in. The transmission does not have a hydraulic slave cylinder so I think it will be a fairly straight forward swap.

My concerns are;
1. Will the gearing be ok for the 300 inline 6 w/ a 3.70 gear?
2. where is the shifter gonna end up at? can I swap out for a different tailshaft that will move the shifter location?
3. driveshaft length?
4. and anything I may be overlooking...

Any help is much appreciated!

[HIO Silver]

Alright here goes, I have a 68' with the 300 inline 6 and a 3 spd. everything works pretty good on it, but I want more overdrive, it has a factory 3.70 geared 9in. rearend. I bought a t-5 transmission that was supposed to have come out of a early 80's mustang gt. I was wondering if anybody could point me in the right direction toward swapping this one in. The transmission does not have a hydraulic slave cylinder so I think it will be a fairly straight forward swap.

My concerns are;
1. Will the gearing be ok for the 300 inline 6 w/ a 3.70 gear?
2. where is the shifter gonna end up at? can I swap out for a different tailshaft that will move the shifter location?
3. driveshaft length?
4. and anything I may be overlooking...

1. An 80s era T-5 will have either a top gear of .72 or .68. Multiplying that to 3.70 equates to final drive ratios of 2.66 and 2.51, respectively. The former is very borderline to be useable and the latter will be a dawg and willl be waaay below the sweet spot of the RPM range. However, MPG will be improved and suitable for the flat lands. A better rear gear is 4.10 which equates it to a 2.80 rear gear... a factory ratio.

2. I believe the shifter will end up in the correct location since the T5 is only an inch or so longer than a C4. You'll need a lengthier shifter arm.

3. Dunno. Long bed or short bed? Nonetheless, the driveshaft length is the last thing to measure. I wouldn't be concerned about it at this point.

http://www.carcraft.com/howto/116_0609_ ... ewall.html
http://www.flatheadv8.org/ernie/ernie-t5.htm

[biggj]

ok thanks for the info
I plan to run a 255/35r20 tire, so that may improve the gear ratio some. I think I will try it out and if it is too bad a set of 4.10 gears shouldn't be a big deal.
sorry about that it is a swb truck, I plan to cut the ibeams out and put a CV IFS in, probably gonna Z the front frame stub 2" or so also.
so you think a bench seat would still work with this tranny?

[HIO Silver]

Oh sorry..... I shouldda read your signature that clearly says SWB.

Bench seat... Yea, I believe it will work out but the bench center is kinda use less for your girl/wife is she wants to sit next to ya - She'll have to straddle the shifter and you'll be busy rowing through the gears. IMO, go buckets with a floor mounted shifter or a bench with a notched center.

Why Z the front clip? That'll get ya lower but it might be too low for day to day use. I wouldn't want to be afraid of every speed bump or driveway I encounter. I think you should re-think that part of your plan or at least verify that the final ride height will be adequate for normal usage. Btw, head over to the Panther platform forum and search for lowering springs. IIRC, Eaton recently came out with a set for the CVs so that can buy an other inch without all the hassle of a front Z.

Lastly, consider doing some body mods to visually lower your 68. The bodies of our F-trucks sit on top of the frame and the lower body lines dive inboard. Adding skirts/rockers can make it look lower without physically being lower.

[biggj]

good point that the middle will be useless as far as the bench goes.
as far as the Z goes, I want to have the front pretty low, I know the CV clip drops it -+5", which judging by some others on here that would put me about 2" or so above the front tire. I want to have the front tire sitting pretty much level with the fender lip. The benefit to the Z is it would keep the suspension geometry pretty much stock without having to install the lowering springs.
I come from the minitruckin' background and have owned several bagged rangers and one sport trac, so one half of me wants to make it a frame dragger! (think marz68)
So just having a low static dropped truck is going to be different for me
I may not Z it, I need to get a CV clip and get it bolted on before cutting the framerails for a Z...
as far as the body kit I will have to respectively decline!
thanks for the help with the gearing, I hope the 5 speed will still be ok when I open it up, it has been sitting out for some time. but hey what can you expect for a $30 transmission...