Your tape drive has also a capstan which went to goo over the past 30 years, so please do not just put them into the drive without fixing that first.
The following are suggestions I'm not implemented, but they seem plausible to me based on other's discussions and some related experience. Please report any results. Consider making another capstan, otherwise called a "pressure roller". In the end, it's a stiff rubber wheel on a bronze bearing with an internal diameter to fit on some roller. Examine your drive or others of same brand and model to determine dimensions. Keep in mind: it's the metal drive roller which determines tape speed, not the roller. It's possible a piece of bronze can be machined to be the correct size, then rubber molded around it, and then carefully machine the rubber to the correct diameter. There are two-part rubber compounds which when mixed and cured are quite stiff. Or, obtain another larger roller and cut it to fit. Rubber can be abraded in a lathe at low speed. Stiff rubber pieces are often sold as furniture bumpers or "corks" for pipe and "test tubes". These machining operations may require practice, and old tape drives can be found to make test rollers - as all you really need to do is drive the capstan motor and monitor tape speed for stability. Any signal on any tape can be watched on an oscilloscope and tape speed determined. A stable signal means tape speed is stable, a wriggly signal means tape speed is varying, probably at the rotation rate of the capstan pressure wheel, or rotation rate of the drive capstan, or due to other irregularities. Herb Johnson -- Herbert R. Johnson, New Jersey USA http://www.retrotechnology.com OR .net