Total Bolt In Astro T5 OD Trans (250 I6) All GM Off the Shelf Parts-1965 C10 SBSS

[Sharps40]

Just checked, I quoted a 27.3% ratio reducer with that 19 tooth driven, 9 tooth drive and 3.73 out back and the 27.4" tall tires.

By some struggling thru the math, I calculate my speedo reads one mph faster than actual.

Watchin Mistress Garmin, the speedo is dead on....likely the speedo ain't accurate enough at nigh onto 50 years old to pick out a mile or three per hour difference anywho.

Luck to ya!

[Sharps40]

In case anybody wonders how a 250 with a T5 pulls and how original drums with power added hold up. Here we go.

Started at 354 feet above sea level...drove Sanford to Asheville NC for Mountain trout fishing and hunting turkeys....170 miles west and we climbed to 2100 feet with no issues. Most of the 6% grades can be conquered with acceleration in fourth gear. A bit steeper and we used third every once in a while, specially for the hair pin turns, always accelerating up even the steepest grades.

No pinging on 10% alkyhall, 89 octane. Mileage out included Interstate and climbing mountains.....17.2 mpg total.

About 80 miles in and around going up and down mountains and hair pins to all the best Trout spots, spent about the entire day pulling in 4th gear, with acceleration up mountain and we changed altitudes regularly of about 1000 feet as we fished valleys to peaks. Topped off with E10 89 octane and checked mileage for the day, about 16.88 mpg.

Coming home, mountain roads and primarily interstate....shed altitude from 2100 ish feet to my home level of 354. Still no issues with power brake drums....rebuilt but all original equipment except for the addition of power booster and dual master from the 1967 time frame. So....who needs discs? Not me. Probably not you either. Tune yer brakes and go drive. About 188 miles home, a bit longer route on the return, holding steady on the interstate at 60 to 65 mpg. Pulled right at 18.5 mpg.

Couldn't think of a better flogging for the engine, trans and tune to see how it runs. Pretty much, seems perfect. Treated John Lee to a tank of 93 octane on arrival home. Good boy, not a drop of oil used or spilled, no ping, no brake fade......a bit like a rowboat in the hairpins and switchbacks if yer goin too hot but manageable with the rebuilt all original suspension.

So, if ya gotta 6 and yer wonderin how it pulls an overdrive....quit worryin and put a T5 in.

I think its time to plan a trip to Devils Tower....in the truck.

[Lugnutz65]

I just sent my Safari T5 (same as an Astro) to a buyer in Texas. I swapped the 0.72 OD gear for what he preferred, an 0.86 OD gear. Swapped the tail housing and shifter mechanism to the S10 variety. He's hooking it up to an inline 6.

Just doing my part to keep these inline sixes rolling with the T5 OD.

[Sharps40]

.86 ain't much....hope he's runnin 3.5 or 3.3 out back.

[Sharps40]

Throwout bearing is in and the T5 is hangin back on the bell. Long story and I'll post up later but a dropped trans and broken release bearing (broken by the 1965 fork bein too thick for the Short bearing groove, more later) and no room for studs in the bell up top but in the bottom worked for reassembly and ratchet straps and quarts of red oil on the floor and in my hair .... I have a new and better made release bearing installed and the fork modded so it won't cam the groove edges and rip the new bearing apart again....I think!

More later. Final assembly tomorrow and then I gotta fix another crapped out rear main seal! I'm getting the silicone seal this time......

[Sharps40]

The first half of the release bearing replacement went like this.

Remove shifter from trans, I left it in gear....that's important later.

Remove ebrake cable and cross member.

Remove drive shaft.

Remove lower clutch rod from the clutch fork.

Strap the trans up with ratchet ties and get the jack ready.

Remove the four bolts holding trans to bell housing....before I can get the studs in it slips back and drops onto the ratchet ties....Guess I had em too tight. (8" studs to slide the trans back on won't fit the top holes, there's too many shapes and fins and stuff stickin out of the side of the tranny, but they will fit the bottom holes, I used studs in the bottom holes, with nuts for reassembly.)

Try not to let the trans drop. Mine eventually rolled back, spilled all the oil and I wound up just takin it out....and cleaning up a bit.

Remove the release bearing.

Upon inspection it seems the failure of the bearing was caused by the fork. Big fat fork for a long bearing with a wider groove riding in a narrower groove short bearing.....as the bearing road back and forth, the thickness of the fork impinged on the bearing groove lips forcing it into its three pieces.

Master Pro 614018 and National 614018 are both short bearings, self centering and 3 piece assembly. The big difference is the Master Pro is held together by simple friction of the beville washer where the National the beville washer has the added advantage of being pressed into a machined groove....so, an interference fit to keep its three pieces together. I spose that's why Master Pro is $13 and National is $41.

[Sharps40]

So, upon inspecting the fork and its relationship to the new and old bearing, I identified real and potential interference points between fork legs and the lips of the bearing grooves.

Time to do some light grinding on the fork. Its hard steel, a file will NOT cut it. Careful grinding is the only way to smooth it up and make room for the fork to swing back and forth in the groove with out the interference that acted like a wedge breaking the first bearing into its component parts.

This is the trans side of the 1965 fork. No interference here, the rear lip of the bearing groove is smaller diameter and clears the nubs at the top and bottom of the fork.



The engine side of the fork had similar nubs. The front lip of the release bearing is much larger in diameter. The front lip and the nubs cammed against each other prying the bearing apart. The simple friction fit of the Bellville washer on the Master Pro bearing was not enough to resist and the bearing separated into three sections. Fortunatly, there is not enough room for it all to fall to pieces and other than very crunchy, I was able to keep driving until I could get inside and fix things.


This is an exaggerated view, photo taken after grinding the noted clearances in the engine side of the fork. The thing to note is with the thick nubs of the original fork in the narrow groove of the bearing, the fork actually acted as a wedge, making the groove wider. Had this been a one piece bearing I suspect it would have simply broken off the lips of the groove.



Here is the old, broken Master Pro 614018 bearing. On the far left you can see, the bearing and the small, friction only beville washer that holds it all together. The new National 614018 is similar but will have the advantage of its beville washer pressed into a matching groove in the collar for an interference/stronger fit and a better fitting fork assembly.

[Sharps40]

So, then the reassembly. No clutch alignment tool. And I needed it because we had reinstalled the bearing and the linkage and cycled the clutch to make sure the fork and bearing relationships were right. Naturally, the clutch disc dropped down out of alignment!

So, in with the clutch pedal and I eyeballed the alignment of the disc with a screwdriver....when it was close, released the clutch to clamp it.

Slid the trans up onto the ratched straps and manhandled it into place alone....it slid in, all but 2.5 inches.....wiggled and wiggled to no avail.

I cut two 1/2x13 TPI studs from thread all. Inserted them thru the lower trans ears and thru the lower bell housing holes. Put a nut on the studs inside the bell housing to keep em there....trans is better aligned and slid in another 1/2" or so....

Loosened the 6 bolts holding the clutch and pressure plate to the flywheel, no help.....so, I removed those 6 bolts after punchmarking the alignment on the flywheel and the pressure plate.

Turn the pressure plate, force it back, turn the clutch disc and it slides back a touch! Shove the trans forward, the lower ears almost make contact. (Having the trans in gear allowed me to verify the clutch was on the splines....as I rotated the pressure plate and the clutch I could feel the output shaft turn and I knew I was home free - A clutch alignment tool woulda been easier but I bring what I got!) Now the bearing is touching the pressure plate fingers....so....

A ratchet strap over the top of the T5 and around the shifter box to the rear engine cross member.... pulling the trans up a bit and forward, clunk, nose of the input shaft slips home in the roller bearing at the rear of the crank.

Now the clutch is clamped back up against the flywheel and so I release tension on the ratchet strap just a touch and the trans slips back about 1/4" and the clutch is released......

I lined up the punch marks on the flywheel and the pressure plate and reinstalled the bolts.

A gentle wiggle and the trans is back up against the bell housing and I installed the four bolts.

Done for the night. I went in, washed up, ate some spam as a reward and collapsed in bed.

Started at 6 PM.....had the bearing and trans back into place with the needed fork mods by 10 PM. We'll finish this job today and see if we can't get a good seal in the rear main and or the loop of the oil pan where it go's over the rear bearing cap.

Wish us luck!

[Sharps40]

Lugnutz65. Takin a break and then finishin the rear main and oil pan (pretty sure it was the rear rubber leakin, lotsa gunk in the corners and no sealant on the rear loop to fill in for a slightly loose rubber seal. Replacin the main seal with a silicone one anyway)....

But I checked my ratio reducer....its marked .73333333333

[Sharps40]

Okay. Just finished the test ride. All seems well. Got the transmission and associated bits locked back down.....everything adjusted.

I set the spacing between the throwout bearing and the fingers of the pressure plate at about 1/4" which is GM spec....I believe. Either way, it provides full clutch release and doesn't nose over or push the collar out so far on the shaft that it catches on the return stroke. Many thanks to GoodWife who lent much moral support and cycled the clutch pedal as I made the final adjustments. The fork does not seems to have any point in it where it would wedge the new bearing groove lips and break it into three pieces.

I have all five gears and reverse, smooth and easy. All the rattle, ticking and crunching are gone.

One thing I noticed....the old trucks are a long throw on the pedal, the Astros are a short throw. I did not adjust for 3/4" free travel on the pedal...it ain't possible with the space left in the bell and in any event, it would severely nose over the clutch and push the bearing off its shaft.

With the spacing of 1/4" from bearing face to clutch fingers, I have perfect function and about 2" or so of free travel up at the pedal. We checked and checked.....the clutch releases perfectly with the shorter stroke. I suppose that stroke is a function of having an Astro clutch pack installed, its a short stroke assembly. In any event....as far as the transmission is concerned, perfect function.

All told, 11 hours start to finish and that time included pulling off the pan and rear main cap to replace the rear seal and pan gasket and pour in all new oil and do the test ride and smoke a cigar.

I wouldn't make any money for a shop at that rate but I have no lift, no tranny jack, no clutch alignment spud. Just some greasy wrenches and just enough strength and stubbornness to get the job done by main force.

Now I need a good part number for an S10 T5 tail shaft seal. The one oriellies sold me is too small.....I had the drive shaft out for the job and I always replace the tail shaft seal everytime I take one out. Any help with the part numbers is appreciated, I'd prefer a National Seal but a good one is fine with me.

[Todd W. White]

Hi Guys!

LOVE this thread!

Questions:

I am running a 1965 Chevy C10 with a rebuilt 283 with an SM420 (also rebuilt), and a 3.08 rear end. I am getting around 16-17 in town, barring bad wind, and 18-21 (usually around 18) on the highway, again barring wind. My original engine was a 235 inline 6. I reused the flywheel, bell housing, starter, and put in a new clutch.

I am thinking of swapping out to the T5, as per this article, and wondered:

1. Will I realize better fuel economy?
2. Will I compromise the strength of my truck? I haul stuff and pull stuff, but don't overdo it.
3. What gear ratio's should I look for?
4. What else should I consider?

THANKS in advance for your help!

- Todd

[Lugnutz65]

Originally Posted by Todd W. White

Hi Guys!

LOVE this thread!

Questions:

I am running a 1965 Chevy C10 with a rebuilt 283 with an SM420 (also rebuilt), and a 3.08 rear end. I am getting around 16-17 in town, barring bad wind, and 18-21 (usually around 18) on the highway, again barring wind. My original engine was a 235 inline 6. I reused the flywheel, bell housing, starter, and put in a new clutch.

I am thinking of swapping out to the T5, as per this article, and wondered:

1. Will I realize better fuel economy?
2. Will I compromise the strength of my truck? I haul stuff and pull stuff, but don't overdo it.
3. What gear ratio's should I look for?
4. What else should I consider?

THANKS in advance for your help!

- Todd

Todd,
As nice as a T5 might be (I have a passion for them), you probably can't beat the setup you already have. The 3.08 rear will give you good highway RPMs and decent MPG with your 3 speed.

To answer your question, a T5 with a 0.72 OD gear works best with a 3.73 rear. If you have a V8 with decent HP, then you could match the 0.72 OD gear with a 3.42 rear.

A T5 with a 0.86 OD gear works great with a 3.42 rear.

The switch to a T5 for you would require a lot of changes. Shorten the drive shaft, cut a hole in the floor, find a way to get the speedometer to work (unless you find one with a cable speedo connection on the S10 tail housing), new pressure plate and clutch disc. Then you would need to swap rear differentials so it would make a good match (per my explanation above).

I recently talked to a guy with the same setup you have. He was very pleased and we both agreed that an OD was not needed.

Sorry if I am raining on your parade.

[Todd W. White]

My 4th gear in the SM420 is 1:1 - but, I'd still like to improve the mileage with an overdrive, but only IF it will make a marked difference.

Using the 283, what would be the "best" gearing to look for in a used transmission, assuming I go with, say, a rear end ratio of 3.52 or so (which I read somewhere is also a possible choice)?

[Lugnutz65]

Originally Posted by Todd W. White

My 4th gear in the SM420 is 1:1 - but, I'd still like to improve the mileage with an overdrive, but only IF it will make a marked difference.

Using the 283, what would be the "best" gearing to look for in a used transmission, assuming I go with, say, a rear end ratio of 3.52 or so (which I read somewhere is also a possible choice)?

Engine RPMs will be the same if you have a small engine, large engine, V8, V6, inline 6 or a 4 cylinder, or whatever. Engine RPMs are based or 4 things. Vehicle speed, transmission gear, rear differential gear and tire size.

Most gasoline engines are happiest cruising on the highway at 2000 to 2400 RPMs. With your current setup, your 283ci engine is probably doing around 2400 RPMs at 65 MPH if you have 28" diameter tires, or 2320 RPMs with 29" diameter tires.

If you swapped in a T5 with a 0.86 OD gear, then the RPMs would drop down to 2066 at 65MPH with a 28" tall tire and 1995 RPMs with a 29" diameter tire. Those numbers are pretty good for a V8 engine. It will work.

The S10 T5 will have a low 1st gear (usually 4.03 or 3.75) and that will work OK too with the 3.08 rear. It will give you a little more power starting off when the light turns green.

Check out my T5 page if you have time.

If you wanted to swap in a T5 from an S10 and use an electric pulse signal speedometer, then that would be the easiest setup to get your speedometer working again. Trying to find an S10 tail housing with the cable speedo connection is the trickiest part if you want to stay with the original factory speedometer. I just saw one sell on eBay for over $200 just for the tail housing alone - not the whole transmission! Yikes!

[luvbowties]

Originally Posted by Todd W. White

My 4th gear in the SM420 is 1:1 - but, I'd still like to improve the mileage with an overdrive, but only IF it will make a marked difference.

Using the 283, what would be the "best" gearing to look for in a used transmission, assuming I go with, say, a rear end ratio of 3.52 or so (which I read somewhere is also a possible choice)?

If I had your present setup(with a 283), was primarily interested in gas mileage, and was getting the mpg you indicated in your 1st post, I'd be tempted to "weld the hood shut" and protect the present combo. Maybe sell picture rights to anyone wishing to copy May luck continue riding with you.
sam

[Sharps40]

Originally Posted by luvbowties

If I had your present setup(with a 283), was primarily interested in gas mileage, and was getting the mpg you indicated in your 1st post, I'd be tempted to "weld the hood shut" and protect the present combo. Maybe sell picture rights to anyone wishing to copy May luck continue riding with you.
sam

Kinday what I was thinkin.....that mileage from an early 8 at 1:1 drive is awesome.

[Todd W. White]

Hello guys! I want to thank everyone for their insights and advice - I don't want to sink a bunch of time and money into something that's not going to help me.

OK - I ran the truck up and down the road, and here are the RPM's. All are in 4th gear, which is a 1.00 gear, and I'm running the 3.08 rear end with 29" tires:

1500 RPM @ 35 MPH
1800 RPM @ 40 MPH
2000 RPM @ 45 MPH
2200 RPM @ 50 MPH
2400 RPM @ 55 MPH
2600 RPM @ 60 MPH
2800 RPM @ 65 MPH

What do you recommend - a T5, a 7500R4 (not really very interested in this one, due to the amount of work it would take to use it), or something else? Another fellow recommended the AZ15.

What say ye?

[Sharps40]

Originally Posted by Sharps40

Kinday what I was thinkin.....that mileage from an early 8 at 1:1 drive is awesome.

I'll just repeat this......

I assume the money is burning a hole in yer pocket....maybe paint the truck?

[Todd W. White]

Follow up -

I talked to Mr. Langdon - wonderful man, by the way, very helpful! - he recommended, based on my current mileage, that I first upgrade my ignition system to HEI from a GM vehicle. My problem is getting one that will fit and not hit the firewall. He was adamantly opposed to ANY of the aftermarket units. Then, he said, see what it's doing and call him back about possible changes in the transmission.

Any suggestions in that department?

THANKS!

- Todd

[Lugnutz65]

Originally Posted by Todd W. White

Hello guys! I want to thank everyone for their insights and advice - I don't want to sink a bunch of time and money into something that's not going to help me.

OK - I ran the truck up and down the road, and here are the RPM's. All are in 4th gear, which is a 1.00 gear, and I'm running the 3.08 rear end with 29" tires:

1500 RPM @ 35 MPH
1800 RPM @ 40 MPH
2000 RPM @ 45 MPH
2200 RPM @ 50 MPH
2400 RPM @ 55 MPH
2600 RPM @ 60 MPH
2800 RPM @ 65 MPH

What do you recommend - a T5, a 7500R4 (not really very interested in this one, due to the amount of work it would take to use it), or something else? Another fellow recommended the AZ15.

What say ye?

I agree with LuvBowties. Your current setup is hard to beat.
If you are absolutely sure your RPMs listed above are correct, then you could do better by lowering the RPMs with a T5 and OD gear.

Personally, I would NOT do anything until you are dead certain (like open the diff and count teeth on the ring and pinion) that you have a 3.08 rear. The RPMs you list are all wrong for a 3.08 rear and a 29" rear tire. You should have 2320 RPMs at 65MPH. Your speedometer could be wrong or your RPMs are wrong or a little of both.

If you are dead set to put a T5 in then go with a 0.86 OD (assuming you really have a 3.08 rear diff).

[Sharps40]

Be interesting to know the actual rear drive ratio...might reveal if the MPG of 18 to 21 is accurate or not. Seems some more info is needed and perhaps a GPS check of actual and indicated speeds at 40, 50 and 60 mph.

But I concur, if its a real 18 to 20, $1000ish for a tranny change seems like money better saved for a nice long vacation in the truck.

[Todd W. White]

I checked my speed with my GPS, and I am within +/- 1 mile per hour in real time on my speedometer. Incidentally, my speedometer was professionally rebuilt by Williamsom's Instruments in Chester, Arkansas, so I know it is correct.

I know the rear end is actually 3.08, because I installed it myself when I still had the inline 6.

The tachometer is a Sun Tach, also rebuilt by Williamsom's Instruments, and upgraded with modern electronics and professionally calibrated.

[Lugnutz65]

Originally Posted by Todd W. White

I checked my speed with my GPS, and I am within +/- 1 mile per hour in real time on my speedometer. Incidentally, my speedometer was professionally rebuilt by Williamsom's Instruments in Chester, Arkansas, so I know it is correct.

I know the rear end is actually 3.08, because I installed it myself when I still have the inline 6.

The tachometer is a Sun Tach, also rebuilt by Williamsom's Instruments, and upgraded with modern electronics and professionally calibrated.

Based on the info you give then we need to look for an explanation as to why the RPMs are off. Gears are not going to give different numbers unless there is slippage somewhere. 2800 RPMs is way too high for 65 MPH with a 29" tire. I know that it sounds like I'm trying to argue, but I'm really only tryoing to prevent a huge waste of money and time. 2320 RPMs at 65 MPH is the only thing that will make sense. Unless there is clutch slippage. Perhaps the Tach is set for a 6 cylinder engine and not for an 8 cylinder?

[Todd W. White]

I wonder if there could be an issue with the tachometer. The reason I say that, it is, because now that you mention it, I remember the RPM's being lower not long ago and they are now at the same speeds. Since the engine does it sound like its running any faster, and I know the speed is pretty close, it makes me suspect the tachometer. I believe that I have a stand-alone tachometer somewhere brand new in a box. Maybe I'll find it, hook it up, and compare.

[Lugnutz65]

Originally Posted by Todd W. White

I wonder if there could be an issue with the tachometer. The reason I say that, it is, because now that you mention it, I remember the RPM's being lower not long ago and they are now at the same speeds. Since I know the speed is pretty close, it makes me suspect the tachometer.

Checking the tach for accuracy would be the easiest first step.